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Lecture notes, cheat sheets
General biology. Lecture notes: briefly, the most important
Directory / Lecture notes, cheat sheets Table of contents
LECTURE #1. Introduction 1. Cell theory (CT) Background of the cell theory The prerequisites for the creation of the cell theory were the invention and improvement of the microscope and the discovery of cells (1665, R. Hooke - when studying a cut of the bark of a cork tree, elderberry, etc.). The works of famous microscopists: M. Malpighi, N. Gru, A. van Leeuwenhoek - made it possible to see the cells of plant organisms. A. van Leeuwenhoek discovered unicellular organisms in water. The cell nucleus was studied first. R. Brown described the nucleus of a plant cell. Ya. E. Purkine introduced the concept of protoplasm - liquid gelatinous cellular contents. The German botanist M. Schleiden was the first to come to the conclusion that every cell has a nucleus. The founder of CT is considered to be the German biologist T. Schwann (together with M. Schleiden), who in 1839 published the work "Microscopic studies on the correspondence in the structure and growth of animals and plants." His provisions: 1) cell - the main structural unit of all living organisms (both animals and plants); 2) if there is a nucleus in any formation visible under a microscope, then it can be considered a cell; 3) the process of formation of new cells determines the growth, development, differentiation of plant and animal cells. Additions to the cellular theory were made by the German scientist R. Virchow, who in 1858 published his work "Cellular Pathology". He proved that daughter cells are formed by division of mother cells: each cell from a cell. At the end of the XIX century. mitochondria, the Golgi complex, and plastids were found in plant cells. Chromosomes were detected after dividing cells were stained with special dyes. Modern provisions of CT 1. Cell - the basic unit of the structure and development of all living organisms, is the smallest structural unit of the living. 2. Cells of all organisms (both unicellular and multicellular) are similar in chemical composition, structure, basic manifestations of metabolism and vital activity. 3. Reproduction of cells occurs by their division (each new cell is formed during the division of the mother cell); in complex multicellular organisms, cells have different shapes and are specialized according to their functions. Similar cells form tissues; tissues consist of organs that form organ systems, they are closely interconnected and subject to nervous and humoral mechanisms of regulation (in higher organisms). Significance of cell theory It became clear that the cell is the most important component of living organisms, their main morphophysiological component. The cell is the basis of a multicellular organism, the place where biochemical and physiological processes take place in the body. At the cellular level, all biological processes ultimately occur. The cell theory made it possible to draw a conclusion about the similarity of the chemical composition of all cells, the general plan of their structure, which confirms the phylogenetic unity of the entire living world. 2. Definition of life at the present stage of development of science It is quite difficult to give a complete and unambiguous definition of the concept of life, given the huge variety of its manifestations. In most definitions of the concept of life, which were given by many scientists and thinkers over the centuries, the leading qualities that distinguish the living from the non-living were taken into account. For example, Aristotle said that life is "nutrition, growth and decrepitude" of the organism; AL Lavoisier defined life as a "chemical function"; G. R. Treviranus believed that life is "a stable uniformity of processes with a difference in external influences." It is clear that such definitions could not satisfy scientists, since they did not reflect (and could not reflect) all the properties of living matter. In addition, observations indicate that the properties of the living are not exceptional and unique, as it seemed before, they are separately found among non-living objects. AI Oparin defined life as "a special, very complex form of matter motion." This definition reflects the qualitative originality of life, which cannot be reduced to simple chemical or physical laws. However, even in this case, the definition is of a general nature and does not reveal the specific peculiarity of this movement. F. Engels in "Dialectics of Nature" wrote: "Life is a mode of existence of protein bodies, the essential point of which is the exchange of matter and energy with the environment." For practical application, those definitions are useful, which contain the basic properties that are necessarily inherent in all living forms. Here is one of them: life is a macromolecular open system, which is characterized by a hierarchical organization, the ability to self-reproduce, self-preservation and self-regulation, metabolism, a finely regulated flow of energy. According to this definition, life is a core of order spreading in a less ordered universe. Life exists in the form of open systems. This means that any living form is not closed only on itself, but constantly exchanges matter, energy and information with the environment. 3. Fundamental properties of living matter These properties in a complex characterize any living system and life in general: 1) self-updating. Associated with the flow of matter and energy. The basis of metabolism is balanced and clearly interconnected processes of assimilation (anabolism, synthesis, formation of new substances) and dissimilation (catabolism, decay). As a result of assimilation, the body structures are updated and new parts (cells, tissues, parts of organs) are formed. Dissimilation determines the breakdown of organic compounds, provides the cell with plastic matter and energy. For the formation of a new one, a constant influx of necessary substances from the outside is needed, and in the process of life (and dissimilation, in particular), products are formed that need to be brought into the external environment; 2) self-reproduction. Provides continuity between successive generations of biological systems. This property is associated with the information flows embedded in the structure of nucleic acids. In this regard, living structures are constantly reproduced and updated, without losing their similarity with previous generations (despite the continuous renewal of matter). Nucleic acids are capable of storing, transmitting and reproducing hereditary information, as well as realizing it through protein synthesis. Information stored on DNA is transferred to a protein molecule with the help of RNA molecules; 3) self-regulation. It is based on a set of flows of matter, energy and information through a living organism; 4) irritability. Associated with the transfer of information from the outside to any biological system and reflects the reaction of this system to an external stimulus. Thanks to irritability, living organisms are able to selectively react to environmental conditions and extract from it only what is necessary for their existence. Irritability is associated with self-regulation of living systems according to the feedback principle: waste products are able to have an inhibitory or stimulating effect on those enzymes that were at the beginning of a long chain of chemical reactions; 5) maintenance of homeostasis (from Gr. homoios - "similar, identical" and stasis - "immobility, state") - the relative dynamic constancy of the internal environment of the body, the physicochemical parameters of the existence of the system; 6) structural organization - a certain orderliness, harmony of a living system. It is found in the study of not only individual living organisms, but also their aggregates in connection with the environment - biogeocenoses; 7) adaptation - the ability of a living organism to constantly adapt to changing conditions of existence in the environment. It is based on irritability and its characteristic adequate responses; 8) reproduction (reproduction). Since life exists in the form of separate (discrete) living systems (for example, cells), and the existence of each such system is strictly limited in time, the maintenance of life on Earth is associated with the reproduction of living systems. At the molecular level, reproduction is carried out due to matrix synthesis, new molecules are formed according to the program laid down in the structure (matrix) of pre-existing molecules; 9) heredity. Provides continuity between generations of organisms (based on information flows). It is closely related to the autoreproduction of life at the molecular, subcellular and cellular levels. Due to heredity, traits are transmitted from generation to generation that provide adaptation to the environment; 10) variability is a property opposite to heredity. Due to variability, a living system acquires features that were previously unusual for it. First of all, variability is associated with errors in reproduction: changes in the structure of nucleic acids lead to the emergence of new hereditary information. New signs and properties appear. If they are useful for an organism in a given habitat, then they are picked up and fixed by natural selection. New forms and types are being created. Thus, variability creates prerequisites for speciation and evolution; 11) individual development (the process of ontogenesis) - the embodiment of the initial genetic information embedded in the structure of DNA molecules (i.e., in the genotype) into the working structures of the body. During this process, such a property as the ability to grow is manifested, which is expressed in an increase in body weight and size. This process is based on the reproduction of molecules, reproduction, growth and differentiation of cells and other structures, etc.; 12) phylogenetic development (its patterns were established by C. R. Darwin). Based on progressive reproduction, heredity, struggle for existence and selection. As a result of evolution, a huge number of species appeared. Progressive evolution has gone through a series of stages. These are pre-cellular, unicellular and multicellular organisms up to humans. At the same time, human ontogeny repeats phylogenesis (i.e., individual development goes through the same stages as the evolutionary process); 13) discreteness (discontinuity) and at the same time integrity. Life is represented by a collection of individual organisms, or individuals. Each organism, in turn, is also discrete, since it consists of a set of organs, tissues and cells. Each cell consists of organelles, but at the same time is autonomous. Hereditary information is carried out by genes, but not a single gene alone can determine the development of a particular trait. 4. Levels of life organization Living nature is an integral, but heterogeneous system, which is characterized by a hierarchical organization. A hierarchical system is such a system in which the parts (or elements of the whole) are arranged in order from highest to lowest. The hierarchical principle of organization makes it possible to single out separate levels in living nature, which is very convenient when studying life as a complex natural phenomenon. There are three main stages of life: microsystems, mesosystems and macrosystems. Microsystems (pre-organism stage) include molecular (molecular-genetic) and subcellular levels. Mesosystems (organismal stage) include cellular, tissue, organ, systemic, organismic (organism as a whole), or ontogenetic, levels. Macrosystems (supraorganismal level) include population-species, biocenotic and global levels (biosphere as a whole). At each level, one can single out an elementary unit and a phenomenon. An elementary unit (EE) is a structure (or object), the regular changes of which (elementary phenomena, EE) make its contribution to the development of life at a given level. Hierarchical levels: 1) molecular genetic level. EE is represented by the genome. A gene is a section of a DNA molecule (and in some viruses, an RNA molecule) that is responsible for the formation of any one trait. The information embedded in nucleic acids is realized through the matrix synthesis of proteins; 2) subcellular level. EE is represented by some subcellular structure, i.e., an organelle that performs its inherent functions and contributes to the work of the cell as a whole; 3) cellular level. EE is a cell, which is an independently functioning elementary biological system. It is only at this level that the realization of genetic information and the processes of biosynthesis are possible. For unicellular organisms, this level coincides with the organism level. EE are the reactions of cellular metabolism, which form the basis of the flows of energy, information and matter; 4) tissue level. A set of cells with the same type of organization constitutes a tissue (EE). The level arose with the advent of multicellular organisms with more or less differentiated tissues. The tissue functions as a whole and has the properties of a living thing; 5) organ level. It is formed together with functioning cells belonging to different tissues (EE). Only four main tissues are part of the organs of multicellular organisms, six main tissues form the organs of plants; 6) organismic (ontogenetic) level. EE is an individual in its development from the moment of birth to the termination of its existence as a living system. EI are regular changes in the body in the process of individual development (ontogenesis). In the process of ontogenesis, under certain environmental conditions, hereditary information is embodied in biological structures, i.e., on the basis of the genotype of an individual, its phenotype is formed; 7) population-species level. EE is a population, i.e., a set of individuals (organisms) of the same species that inhabit the same territory and freely interbreed. The population has a gene pool, i.e., the totality of the genotypes of all individuals. The impact on the gene pool of elementary evolutionary factors (mutations, fluctuations in the number of individuals, natural selection) leads to evolutionarily significant changes (ER); 8) biocenotic (ecosystem) level. EE - biocenosis, i.e., a historically established stable community of populations of different species, connected with each other and with the surrounding inanimate nature by the exchange of substances, energy and information (cycles), which represent the EE; 9) biosphere (global) level. EE - the biosphere (the area of \uXNUMXb\uXNUMXbdistribution of life on Earth), that is, a single planetary complex of biogeocenoses, different in species composition and characteristics of the abiotic (non-living) part. Biogeocenoses determine all processes occurring in the biosphere; 10) nospheric level. This new concept was formulated by Academician V. I. Vernadsky. He founded the doctrine of the noosphere as the sphere of the mind. This is an integral part of the biosphere, which is changed due to human activity. LECTURE № 2. Chemical composition of living systems. The biological role of proteins, polysaccharides, lipids and ATP 1. Overview of the chemical structure of the cell All living systems contain chemical elements in various proportions and chemical compounds built from them, both organic and inorganic. According to the quantitative content in the cell, all chemical elements are divided into 3 groups: macro-, micro- and ultramicroelements. Macronutrients make up to 99% of the cell mass, of which up to 98% is accounted for by 4 elements: oxygen, nitrogen, hydrogen and carbon. In smaller quantities, cells contain potassium, sodium, magnesium, calcium, sulfur, phosphorus, and iron. Trace elements are predominantly metal ions (cobalt, copper, zinc, etc.) and halogens (iodine, bromine, etc.). They are contained in amounts from 0,001% to 0,000001%. Ultramicroelements. Their concentration is below 0,000001%. These include gold, mercury, selenium, etc. A chemical compound is a substance in which the atoms of one or more chemical elements are connected to each other through chemical bonds. Chemical compounds are inorganic and organic. Inorganic include water and mineral salts. Organic compounds are compounds of carbon with other elements. The main organic compounds of the cell are proteins, fats, carbohydrates and nucleic acids. 2. Biopolymers Proteins These are polymers whose monomers are amino acids. They are mainly composed of carbon, hydrogen, oxygen and nitrogen. A protein molecule can have 4 levels of structural organization (primary, secondary, tertiary and quaternary structures). Protein functions: 1) protective (interferon is intensively synthesized in the body during a viral infection); 2) structural (collagen is part of tissues, participates in scar formation); 3) motor (myosin is involved in muscle contraction); 4) spare (egg albumins); 5) transport (erythrocyte hemoglobin carries nutrients and metabolic products); 6) receptor (receptor proteins provide recognition by the cell of substances and other cells); 7) regulatory (regulatory proteins determine the activity of genes); 8) hormone proteins are involved in humoral regulation (insulin regulates blood sugar levels); 9) enzyme proteins catalyze all chemical reactions in the body; 10) energy (the breakdown of 1 g of protein releases 17 kJ of energy). Carbohydrates These are mono- and polymers, which include carbon, hydrogen and oxygen in a ratio of 1: 2: 1. Functions of carbohydrates: 1) energy (with the breakdown of 1 g of carbohydrates, 17,6 kJ of energy is released); 2) structural (cellulose, which is part of the cell wall in plants); 3) storage (supply of nutrients in the form of starch in plants and glycogen in animals). Fats Fats (lipids) can be simple or complex. Simple lipid molecules are composed of the trihydric alcohol glycerol and three fatty acid residues. Complex lipids are compounds of simple lipids with proteins and carbohydrates. Lipid functions: 1) energy (with the breakdown of 1 g of lipids, 38,9 kJ of energy is formed); 2) structural (phospholipids of cell membranes forming a lipid bilayer); 3) storage (supply of nutrients in the subcutaneous tissue and other organs); 4) protective (subcutaneous tissue and a layer of fat around the internal organs protect them from mechanical damage); 5) regulatory (hormones and vitamins containing lipids regulate metabolism); 6) heat-insulating (subcutaneous tissue retains heat). ATP The ATP (adenosine triphosphoric acid) molecule consists of the nitrogenous base of adenine, the five-carbon sugar of ribose, and three phosphoric acid residues interconnected by a macroergic bond. ATP is produced in mitochondria by phosphorylation. During its hydrolysis, a large amount of energy is released. ATP is the main macroerg of the cell - an energy accumulator in the form of energy of high-energy chemical bonds. LECTURE № 3. Nucleic acids. Protein biosynthesis Nucleic acids are phosphorus-containing biopolymers whose monomers are nucleotides. Nucleic acid chains include from several tens to hundreds of millions of nucleotides. There are 2 types of nucleic acids - deoxyribo-nucleic acid (DNA) and ribonucleic acid (RNA). The nucleotides that make up DNA contain a carbohydrate, deoxy-ribose, while RNA contains ribose. 1. DNA As a rule, DNA is a helix consisting of two complementary polynucleotide chains twisted to the right. The composition of DNA nucleotides includes: a nitrogenous base, deoxyribose and a phosphoric acid residue. Nitrogenous bases are divided into purine (adenine and guanine) and pyrimidine (thymine and cytosine). Two chains of nucleotides are connected to each other through nitrogenous bases according to the principle of complementarity: two hydrogen bonds occur between adenine and thymine, and three between guanine and cytosine. DNA functions: 1) ensures the preservation and transmission of genetic information from cell to cell and from organism to organism, which is associated with its ability to replicate; 2) regulation of all processes occurring in the cell, provided by the ability to transcription with subsequent translation. The process of self-reproduction (auto-reproduction) of DNA is called replication. Replication ensures the copying of genetic information and its transmission from generation to generation, the genetic identity of daughter cells formed as a result of mitosis, and the constancy of the number of chromosomes during mitotic cell division. Replication occurs during the synthetic period of the interphase of mitosis. The replicase enzyme moves between the two strands of the DNA helix and breaks the hydrogen bonds between the nitrogenous bases. Then, to each of the chains, using the DNA polymerase enzyme, the nucleotides of the daughter chains are completed according to the principle of complementarity. As a result of replication, two identical DNA molecules are formed. The amount of DNA in a cell doubles. This method of DNA duplication is called semi-conservative, since each new DNA molecule contains one "old" and one newly synthesized polynucleotide chain. 2. RNA RNA is a single-stranded polymer whose monomers include purine (adenine, guanine) and pyrimidine (uracil, cytosine) nitrogenous bases, a ribose carbohydrate, and a phosphoric acid residue. There are 3 types of RNA: information, transport and ribosomal. Messenger RNA (i-RNA) is located in the nucleus and cytoplasm of the cell, has the longest polynucleotide chain among RNA and performs the function of transferring hereditary information from the nucleus to the cytoplasm of the cell. Transfer RNA (t-RNA) is also found in the nucleus and cytoplasm of the cell, its chain has the most complex structure, and is also the shortest (75 nucleotides). T-RNA delivers amino acids to ribosomes during translation - protein biosynthesis. Ribosomal RNA (r-RNA) is found in the nucleolus and ribosomes of the cell, has a chain of medium length. All types of RNA are formed during the transcription of the corresponding DNA genes. 3. Protein biosynthesis Protein biosynthesis in eukaryotes occurs in several stages. 1. Transcription is the process of mRNA synthesis on a DNA template. DNA chains in the region of the active gene are freed from histones. Hydrogen bonds between complementary nitrogenous bases are broken. The main transcription enzyme, RNA polymerase, attaches to a promoter, a special section of DNA. Transcription takes place only from one (codogenic) DNA strand. As RNA polymerase moves along the codogenic DNA strand, ribonucleotides join the DNA strand according to the principle of complementarity, resulting in the formation of an immature pro-i-RNA containing both coding and non-coding nucleotide sequences. 2. Then processing occurs - the maturation of the RNA molecule. At the 5-end of the mRNA, a site (CEP) is formed through which it connects to the ribosome. A gene, that is, a section of DNA encoding one protein, contains both coding nucleotide sequences - exons, and non-coding sequences - introns. During processing, introns are excised and exons are fused. As a result, at the 5-end of the mature mRNA there is an initiator codon, which will be the first to enter the ribosome, then there are codons encoding the amino acids of the polypeptide, and at the 3-end there are terminator codons that determine the end of translation. Numbers 3 and 5 denote the corresponding carbon atoms of ribose. A codon is a sequence of three nucleotides encoding an amino acid - a triplet. The nucleic acid reading frame assumes "words" - triplets (codons) consisting of three "letters" - nucleotides. Transcription and processing take place in the nucleus of the cell. The mature mRNA then enters the cytoplasm through pores in the nuclear membrane, and translation begins. 3. Translation is the process of protein synthesis on the matrix and RNA. At the beginning, the mRNA attaches to the ribosome at the 3-end. T-RNA is delivered to the acceptor site of the ribosome of amino acids, which are combined into a polypeptide chain in accordance with the codons that encode them. The growing polypeptide chain moves to the donor site of the ribosome, and a new t-RNA with an amino acid comes to the acceptor site. Translation is terminated at terminator codons. Genetic code This is a system for encoding the amino acid sequence of a protein as a specific sequence of nucleotides in DNA and RNA. A unit of the genetic code (codon) is a triplet of nucleotides in DNA or RNA that codes for one amino acid. In total, the genetic code includes 64 codons, of which 61 are coding and 3 are non-coding (terminator codons indicating the end of the translation process). Terminator codons in i-RNA: UAA, UAG, UGA, in DNA: ATT, ATC, ACT. The beginning of the translation process is determined by the initiator codon (AUG, in DNA - TAC), encoding the amino acid methionine. This codon is the first to enter the ribosome. Subsequently, methionine, if it is not provided as the first amino acid of this protein, is cleaved off. The genetic code has characteristic properties. 1. Universality - the code is the same for all organisms. The same triplet (codon) in any organism codes for the same amino acid. 2. Specificity - each codon codes for only one amino acid. 3. Degeneracy - most amino acids can be encoded by several codons. The exception is 2 amino acids - methionine and tryptophan, which have only one codon variant each. 4. Between the genes there are "punctuation marks" - three special triplets (UAA, UAG, UGA), each of which indicates the termination of the synthesis of the polypeptide chain. 5. There are no "punctuation marks" inside the gene. LECTURE No. 4. Basic cell forms 1. Prokaryotes All living organisms on Earth are usually divided into pre-cellular forms that do not have a typical cellular structure (these are viruses and bacteriophages), and cellular forms that have a typical cellular structure. These organisms, in turn, are divided into two categories: 1) prenuclear prokaryotes that do not have a typical nucleus. These include bacteria and blue-green algae; 2) nuclear eukaryotes, which have a typical well-defined nucleus. These are all other organisms. Prokaryotes arose much earlier than eukaryotes (in the Archean era). These are very small cells ranging in size from 0,1 to 10 microns. Sometimes there are giant cells up to 200 microns. A typical bacterial cell is surrounded on the outside by a cell wall, the basis of which is the substance murein (a polysaccharide is a complex carbohydrate). The cell wall determines the shape of the bacterial cell. On top of the cell wall there is a mucous capsule, or mucous layer, which performs a protective function. Under the cell wall is the plasma membrane (see its structure in eukaryotes). The entire cell inside is filled with cytoplasm, which consists of a liquid part (hyaloplasm, or matrix), organelles and inclusions. Hyaloplasm is a colloidal solution of biomolecules that can exist in two states: sol (under favorable conditions) and gel (under bad conditions, when the density of the hyaloplasm increases). Hereditary apparatus: one large "naked", devoid of protective proteins, DNA molecule, closed in a ring - nucleoid. In the hyaloplasm of some bacteria there are also short circular DNA molecules that are not associated with a chromosome or nucleoid - plasmids. There are few membrane organelles in prokaryotic cells. There are mesosomes - internal outgrowths of the plasma membrane, which are considered the functional equivalents of eukaryotic mitochondria. In autotrophic prokaryotes - cyanobacteria and others - lamellas and lamelosomes are found - photosynthetic membranes. They contain the pigments chlorophyll and phycocyanin. Many non-membranous organelles are found. Ribosomes, like those of eukaryotes, consist of two subunits: large and small. They are small in size, randomly located in the hyaloplasm. Ribosomes are responsible for the synthesis of bacterial proteins. Some bacteria have organelles of movement - flagella, which are built from microfilaments. Bacteria have recognition organelles - pili (fimbria), which are located outside the cell and are thin hair-like outgrowths. The hyaloplasm also contains non-permanent inclusions: protein granules, fat drops, polysaccharide molecules, salts. 2. General information about the eukaryotic cell Each eukaryotic cell has a separate nucleus, which contains genetic material separated from the matrix by a nuclear membrane (this is the main difference from prokaryotic cells). The genetic material is concentrated mainly in the form of chromosomes, which have a complex structure and consist of DNA strands and protein molecules. Cell division occurs through mitosis (and for germ cells - meiosis). Eukaryotes include both unicellular and multicellular organisms. There are several theories of the origin of eukaryotic cells, one of them is endosymbiontic. An aerobic cell of the bacterio-like type penetrated into the heterotrophic anaerobic cell, which served as the basis for the appearance of mitochondria. Spirochete-like cells began to penetrate into these cells, which gave rise to the formation of centrioles. The hereditary material was fenced off from the cytoplasm, a nucleus arose, mitosis appeared. Some eukaryotic cells were invaded by cells such as blue-green algae, which gave rise to chloroplasts. This is how the plant kingdom came into being. The size of the cells of the human body varies from 2-7 microns (for platelets) to gigantic sizes (up to 140 microns for an egg). The shape of the cells is determined by the function they perform: nerve cells are stellate due to the large number of processes (axon and dendrites), muscle cells are elongated, as they must contract, erythrocytes can change their shape when moving through small capillaries. The structure of eukaryotic cells of animal and plant organisms is similar in many respects. Each cell is externally bounded by a cell membrane, or plasmalemma. It consists of a cytoplasmic membrane and a layer of glycocalyx (10–20 nm thick) that covers it from the outside. The components of the glycocalyx are complexes of polysaccharides with proteins (glycoproteins) and fats (glycolipids). The cytoplasmic membrane is a complex of a bilayer of phospholipids with proteins and polysaccharides. The cell has a nucleus and cytoplasm. The cell nucleus consists of a membrane, nuclear sap, nucleolus and chromatin. The nuclear envelope consists of two membranes separated by a peri-nuclear space and is permeated with pores. The basis of the nuclear juice (matrix) is made up of proteins: filamentous, or fibrillar (support function), globular, heteronuclear RNA and mRNA (the result of processing). The nucleolus is the structure where the formation and maturation of ribosomal RNA (rRNA) takes place. Chromatin in the form of clumps is scattered in the nucleoplasm and is an interphase form of the existence of chromosomes. In the cytoplasm, the main substance (matrix, hyaloplasm), organelles and inclusions are isolated. Organelles can be of general importance and special (in cells that perform specific functions: microvilli of the absorbing intestinal epithelium, myofibrils of muscle cells, etc.). Organelles of general importance - the endoplasmic reticulum (smooth and rough), the Golgi complex, mitochondria, ribosomes and polysomes, lysosomes, peroxisomes, microfibrils and microtubules, centrioles of the cell center. Plant cells also contain chloroplasts, where photosynthesis takes place. 3. Functions and structure of the cytoplasmic membrane The elementary membrane consists of a bilayer of lipids in complex with proteins (glycoproteins: proteins + carbohydrates, lipoproteins: fats + proteins). Among lipids, phospholipids, cholesterol, glycolipids (carbohydrates + fats), lipoproteins can be distinguished. Each fat molecule has a polar hydrophilic head and a non-polar hydrophobic tail. In this case, the molecules are oriented so that the heads are turned outward and inside the cell, and the non-polar tails are turned inside the membrane itself. This achieves selective permeability for substances entering the cell. Peripheral proteins are isolated (they are located only on the inner or outer surface of the membrane), integral (they are firmly embedded in the membrane, immersed in it, able to change their position depending on the state of the cell). Functions of membrane proteins: receptor, structural (support the shape of the cell), enzymatic, adhesive, antigenic, transport. The structural scheme of the elementary membrane is liquid-mosaic: fats make up a liquid-crystalline frame, and proteins are mosaically embedded in it and can change their position. The most important function: promotes compartmentation - the division of the contents of the cell into separate cells, differing in the details of the chemical or enzymatic composition. This achieves a high orderliness of the internal contents of any eukaryotic cell. Compartmentation contributes to the spatial separation of processes occurring in the cell. A separate compartment (cell) is represented by some membrane organelle (for example, a lysosome) or its part (cristae delimited by the inner membrane of mitochondria). Other features: 1) barrier (delimitation of the internal contents of the cell); 2) structural (giving a certain shape to cells in accordance with the functions performed); 3) protective (due to selective permeability, reception and antigenicity of the membrane); 4) regulatory (regulation of selective permeability for various substances (passive transport without energy expenditure according to the laws of diffusion or osmosis and active transport with energy expenditure by pinocytosis, endo- and exocytosis, the operation of the sodium-potassium pump, phagocytosis)); 5) adhesive function (all cells are interconnected through specific contacts (tight and loose)); 6) receptor (due to the work of peripheral membrane proteins). There are non-specific receptors that perceive several stimuli (for example, cold and heat thermoreceptors), and specific ones that perceive only one stimulus (receptors of the light-perceiving system of the eye); 7) electrogenic (change in the electrical potential of the cell surface due to the redistribution of potassium and sodium ions (the membrane potential of nerve cells is 90 mV)); 8) antigenic: associated with glycoproteins and membrane polysaccharides. On the surface of each cell there are protein molecules that are specific only for this type of cell. With their help, the immune system is able to distinguish between self and foreign cells. 4. Structure and functions of the cell nucleus The nucleus is in any eukaryotic cell. The kernel may be one, or there may be several cores in the cell (depending on its activity and function). The cell nucleus consists of a shell, nuclear juice, nucleolus and chromatin. The nuclear envelope consists of two membranes separated by perinuclear (near-nuclear) space, between which there is liquid. The main functions of the nuclear envelope are the isolation of the genetic material (chromosomes) from the cytoplasm, as well as the regulation of the bilateral relationships between the nucleus and the cytoplasm. The nuclear envelope is permeated with pores that have a diameter of about 90 nm. The pore area (pore complex) has a complex structure (this indicates the complexity of the mechanism for regulating the relationship between the nucleus and the cytoplasm). The number of pores depends on the functional activity of the cell: the higher it is, the more pores (there are more pores in immature cells). The basis of nuclear juice (matrix, nucleoplasm) is proteins. Juice forms the internal environment of the nucleus, plays an important role in the work of the genetic material of cells. Proteins: filamentous or fibrillar (support function), heteronuclear RNA (products of primary transcription of genetic information) and mRNA (processing result). The nucleolus is the structure where the formation and maturation of ribosomal RNA (rRNA) takes place. The rRNA genes occupy certain sections of several chromosomes (in humans, these are 13-15 and 21-22 pairs), where nucleolar organizers are formed, in the region of which the nucleoli themselves are formed. In metaphase chromosomes, these areas are called secondary constrictions and look like constrictions. Electron microscopy revealed filamentous and granular components of the nucleoli. Filamentous (fibrillar) is a complex of proteins and giant rRNA precursor molecules, which subsequently give rise to smaller molecules of mature rRNA. During maturation, the fibrils are transformed into ribonucleoprotein granules (granular component). Chromatin got its name for its ability to stain well with basic dyes; in the form of clumps, it is scattered in the nucleoplasm of the nucleus and is an interphase form of the existence of chromosomes. Chromatin consists mainly of DNA strands (40% of the mass of the chromosome) and proteins (about 60%), which together form the nucleoprotein complex. There are histone (five classes) and non-histone proteins. Histones (40%) have regulatory (strongly connected to DNA and prevent reading information from it) and structural functions (organization of the spatial structure of the DNA molecule). Non-histone proteins (more than 100 fractions, 20% of the chromosome mass): enzymes of RNA synthesis and processing, DNA replication repair, structural and regulatory functions. In addition, RNA, fats, polysaccharides, and metal molecules were found in the composition of chromosomes. Depending on the state of chromatin, euchromatic and heterochromatic regions of chromosomes are distinguished. Euchromatin is less dense and genetic information can be read from it. Heterochromatin is more compact, and information cannot be read within it. There are constitutive (structural) and facultative heterochromatin. 5. Structure and functions of semi-autonomous cell structures: mitochondria and plastids Mitochondria (from Gr. mitos - "thread", chondrion - "seed, grain") are permanent membrane organelles of a round or rod-shaped (often branching) shape. Thickness - 0,5 microns, length - 5-7 microns. The number of mitochondria in most animal cells is 150-1500; in female eggs - up to several hundred thousand, in spermatozoa - one helical mitochondria twisted around the axial part of the flagellum. The main functions of mitochondria: 1) play the role of energy stations of cells. They are the processes of oxidative phosphorylation (enzymatic oxidation of various substances with subsequent accumulation of energy in the form of molecules of adenosine triphosphate - ATP); 2) store hereditary material in the form of mitochondrial DNA. Mitochondria require the proteins encoded in the nuclear DNA genes to function, since their own mitochondrial DNA can provide mitochondria with only a few proteins. Side functions - participation in the synthesis of steroid hormones, some amino acids (for example, glutamine). The structure of mitochondria Mitochondria have two membranes: outer (smooth) and inner (forming outgrowths - leaf-shaped (cristae) and tubular (tubules)). Membranes differ in chemical composition, set of enzymes and functions. In mitochondria, the internal content is a matrix - a colloidal substance in which grains with a diameter of 20-30 nm were found using an electron microscope (they accumulate calcium and magnesium ions, reserves of nutrients, for example, glycogen). The matrix houses the organelle protein biosynthesis apparatus: 2-6 copies of circular DNA devoid of histone proteins (like in prokaryotes), ribosomes, a set of t-RNA, enzymes of reduplication, transcription, translation of hereditary information. This apparatus as a whole is very similar to that of prokaryotes (in terms of the number, structure and size of ribosomes, the organization of its own hereditary apparatus, etc.), which confirms the symbiotic concept of the origin of the eukaryotic cell. Both the matrix and the surface of the inner membrane are actively involved in the implementation of the energy function of mitochondria, on which the electron transport chain (cytochromes) and ATP synthase are located, which catalyzes the phosphorylation of ADP coupled with oxidation, which converts it into ATP. Mitochondria multiply by ligation, so during cell division they are more or less evenly distributed between daughter cells. Thus, succession is carried out between the mitochondria of cells of successive generations. Thus, mitochondria are characterized by relative autonomy within the cell (unlike other organelles). They arise during the division of maternal mitochondria, have their own DNA, which differs from the nuclear system of protein synthesis and energy storage. Plastids These are semi-autonomous structures (they can exist relatively autonomously from the cell's nuclear DNA) that are present in plant cells. They are formed from proplastids, which are present in the embryo of the plant. Delimited by two membranes. There are three groups of plastids: 1) leukoplasts. They are round, not colored and contain nutrients (starch); 2) chromoplasts. They contain molecules of coloring substances and are present in the cells of colored plant organs (fruits of cherries, apricots, tomatoes); 3) chloroplasts. These are the plastids of the green parts of the plant (leaves, stems). In structure, they are in many ways similar to the mitochondria of animal cells. The outer membrane is smooth, the inner one has outgrowths - lamelosomes, which end in thickenings - thylakoids containing chlorophyll. The stroma (liquid part of the chloroplast) contains a circular DNA molecule, ribosomes, reserve nutrients (starch grains, fat drops). 6. Structure and functions of lysosomes and peroxisomes. Lysosomes Lysosomes (from Gr. lysis - "decomposition, dissolution, decay" and soma - "body") are vesicles with a diameter of 200-400 microns. (usually). They have a single-membrane shell, which is sometimes covered on the outside with a fibrous protein layer. They contain a set of enzymes (acid hydrolases) that carry out hydrolytic (in the presence of water) cleavage of substances (nucleic acids, proteins, fats, carbohydrates) at low pH values. The main function is the intracellular digestion of various chemical compounds and cellular structures. There are primary (inactive) and secondary lysosomes (the process of digestion takes place in them). Secondary lysosomes are formed from primary ones. They are divided into heterolysosomes and autolysosomes. In heterolysosomes (or phagolysosomes), the process of digestion of material that enters the cell from the outside by active transport (pinocytosis and phagocytosis) takes place. In autolysosomes (or cytolysosomes), their own cellular structures that have completed their lives are destroyed. Secondary lysosomes that have already stopped digesting material are called residual bodies. They do not contain hydro-lases, they contain undigested material. In case of violation of the integrity of the lysosome membrane or in case of a disease, hydrolase cells enter the cell from lysosomes and carry out its self-digestion (autolysis). The same process underlies the process of natural death of all cells (apoptosis). microbody Microbodies make up a group of organelles. They are bubbles with a diameter of 100-150 nm, delimited by one membrane. They contain a fine-grained matrix and often protein inclusions. These organelles include peroxisomes. They contain enzymes of the oxidase group that regulate the formation of hydrogen peroxide (in particular, catalase). Since hydrogen peroxide is a toxic substance, it undergoes cleavage under the action of peroxidase. The reactions of formation and breakdown of hydrogen peroxide are included in many metabolic cycles, especially active in the liver and kidneys. Therefore, in the cells of these organs, the number of peroxisomes reaches 70-100. 7. The structure and functions of the endoplasmic reticulum, the Golgi complex Endoplasmic reticulum Endoplasmic reticulum (EPS) - a system of communicating or separate tubular channels and flattened cisterns located throughout the cytoplasm of the cell. They are delimited by membranes (membrane organelles). Sometimes tanks have expansions in the form of bubbles. EPS channels can connect with surface or nuclear membranes, contact with the Golgi complex. In this system, smooth and rough (granular) EPS can be distinguished. Rough XPS On the channels of the rough ER, ribosomes are located in the form of polysomes. Here, the synthesis of proteins occurs, mainly produced by the cell for export (removal from the cell), for example, secretions of glandular cells. Here, the formation of lipids and proteins of the cytoplasmic membrane and their assembly take place. The densely packed cisterns and channels of the granular ER form a layered structure where protein synthesis proceeds most actively. This place is called ergastoplasm. Smooth EPS There are no ribosomes on smooth ER membranes. Here, mainly the synthesis of fats and similar substances (for example, steroid hormones), as well as carbohydrates, proceeds. Through the channels of smooth EPS, the finished material also moves to the place of its packaging into granules (to the zone of the Golgi complex). In hepatic cells, smooth ER takes part in the destruction and neutralization of a number of toxic and medicinal substances (for example, barbiturates). In the striated muscles, the tubules and cisterns of the smooth ER deposit calcium ions. Golgi complex The Golgi lamellar complex is the packing center of the cell. It is a collection of dictyosomes (from several tens to hundreds and thousands per cell). Dictyosome - a stack of 3-12 flattened oval cisterns, along the edges of which are small vesicles (vesicles). Larger cisternae extensions give rise to vacuoles containing the cell's water reserve and responsible for maintaining turgor. The lamellar complex gives rise to secretory vacuoles, which contain substances intended for removal from the cell. At the same time, the prosecret entering the vacuole from the synthesis zone (EPS, mitochondria, ribosomes) undergoes some chemical transformations here. The Golgi complex gives rise to primary lysosomes. Dictyosomes also synthesize polysaccharides, glycoproteins and glycolipids, which are then used to build cytoplasmic membranes. 8. Structure and functions of non-membrane cell structures This group of organelles includes ribosomes, microtubules and microfilaments, the cell center. Ribosome It is a rounded ribonucleoprotein particle. Its diameter is 20-30 nm. The ribosome consists of large and small subunits, which combine in the presence of a strand of mRNA (matrix, or informational, RNA). The complex of a group of ribosomes united by a single mRNA molecule like a string of beads is called a polysome. These structures are either freely located in the cytoplasm or attached to the membranes of the granular ER (in both cases, protein synthesis actively proceeds on them). Polysomes of granular ER form proteins that are excreted from the cell and used for the needs of the whole organism (for example, digestive enzymes, proteins of human breast milk). In addition, ribosomes are present on the inner surface of mitochondrial membranes, where they also take an active part in the synthesis of protein molecules. Microtubules These are tubular hollow formations devoid of a membrane. The outer diameter is 24 nm, the lumen width is 15 nm, and the wall thickness is about 5 nm. In the free state, they are present in the cytoplasm; they are also structural elements of the flagella, centrioles, spindle, and cilia. Microtubules are built from stereotyped protein subunits by polymerization. In any cell, polymerization processes run parallel to depolymerization processes. Moreover, their ratio is determined by the number of microtubules. Microtubules have varying degrees of resistance to damaging factors such as colchicine (a chemical that causes depolymerization). Functions of microtubules: 1) are the supporting apparatus of the cell; 2) determine the shape and size of the cell; 3) are factors of directed movement of intracellular structures. Microfilaments These are thin and long formations that are found throughout the cytoplasm. Sometimes they form bundles. Types of micro-filaments: 1) actin. They contain contractile proteins (actin), provide cellular forms of movement (for example, amoeboid), play the role of a cell scaffold, participate in organizing the movements of organelles and sections of the cytoplasm inside the cell; 2) intermediate (10 nm thick). Their bundles are found along the periphery of the cell under the plasmalemma and along the circumference of the nucleus. They perform a supporting (framework) role. In different cells (epithelial, muscle, nerve, fibroblasts) they are built from different proteins. Microfilaments, like microtubules, are built from subunits, so their number is determined by the ratio of polymerization and depolymerization processes. The cells of all animals, some fungi, algae, higher plants are characterized by the presence of a cell center. The cell center is usually located near the nucleus. It consists of two centrioles, each of which is a hollow cylinder with a diameter of about 150 nm and a length of 300-500 nm. The centrioles are mutually perpendicular. The wall of each centriole is formed by 27 microtubules, consisting of the protein tubulin. Microtubules are grouped into 9 triplets. Spindle threads are formed from the centrioles of the cell center during cell division. Centrioles polarize the process of cell division, thereby achieving a uniform divergence of sister chromosomes (chromatids) in the anaphase of mitosis. 9. Hyaloplasm - the internal environment of the cell. Cytoplasmic inclusions Inside the cell is the cytoplasm. It consists of a liquid part - hyaloplasm (matrix), organelles and cytoplasmic inclusions. Hyaloplasm Hyaloplasm - the main substance of the cytoplasm, fills the entire space between the plasma membrane, the shell of the nucleus and other intracellular structures. Hyaloplasm can be considered as a complex colloidal system that can exist in two states: sol-like (liquid) and gel-like, which mutually transform one into another. In the process of these transitions, certain work is carried out, energy is expended. Hyaloplasm is devoid of any specific organization. The chemical composition of the hyaloplasm: water (90%), proteins (enzymes of glycolysis, sugar metabolism, nitrogenous bases, proteins and lipids). Some cytoplasmic proteins form subunits that give rise to such organelles as centrioles, microfilaments. Hyaloplasmic functions: 1) the formation of a true internal environment of the cell, which unites all organelles and ensures their interaction; 2) maintaining a certain structure and shape of the cell, creating a support for the internal arrangement of organelles; 3) ensuring intracellular movement of substances and structures; 4) ensuring adequate metabolism both within the cell itself and with the external environment. Inclusions These are relatively unstable components of the cytoplasm. Among them are: 1) reserve nutrients that are used by the cell itself during periods of insufficient intake of nutrients from the outside (during cellular starvation) - drops of fat, starch or glycogen granules; 2) products that are to be released from the cell, for example, mature secretion granules in secretory cells (milk in lactocytes of the mammary glands); 3) ballast substances of some cells that do not perform any specific function (some pigments, for example, lipofuscin of senescent cells). LECTURE No. 5. Non-cellular life forms - viruses, bacteriophages Viruses are precellular life forms that are obligate intracellular parasites, that is, they can exist and multiply only inside the host organism. Viruses were discovered by D. I. Ivanovsky in 1892 (he studied the tobacco mosaic virus), but their existence was proved much later. Many viruses are the causative agents of diseases such as AIDS, rubella measles, mumps (mumps), chickenpox and smallpox. Viruses are microscopic in size, many of them are able to pass through any filters. Unlike bacteria, viruses cannot be grown on nutrient media, since outside the body they do not exhibit the properties of a living thing. Outside a living organism (host), viruses are crystals of substances that do not have any properties of living systems. The structure of viruses Mature viral particles are called virions. In fact, they are a genome covered with a protein coat on top. This shell is the capsid. It is built from protein molecules that protect the genetic material of the virus from the effects of nucleases - enzymes that destroy nucleic acids. Some viruses have a super-capsid shell on top of the capsid, also built from protein. The genetic material is represented by nucleic acid. In some viruses, this is DNA (the so-called DNA viruses), in others it is RNA (RNA viruses). RNA viruses are also called retroviruses, since the synthesis of viral proteins in this case requires reverse transcription, which is carried out by the enzyme - reverse transcriptase (revertase) and is a DNA synthesis based on RNA. Virus propagation When the virus enters the host cell, the nucleic acid molecule is released from the protein, so only pure and unprotected genetic material enters the cell. If the virus is DNA, then the DNA molecule is integrated into the host's DNA molecule and reproduces along with it. This is how new viral DNA appears, indistinguishable from the original. All processes occurring in the cell slow down, the cell begins to work on the reproduction of the virus. Since the virus is an obligate parasite, a host cell is necessary for its life, so it does not die in the process of virus reproduction. Cell death occurs only after the release of viral particles from it. If it is a retrovirus, its RNA enters the host cell. It contains genes that provide reverse transcription: a single-stranded DNA molecule is built on an RNA template. From the free nucleotides, a complementary chain is completed, which is integrated into the genome of the host cell. From the resulting DNA, the information is rewritten to the mRNA molecule, on the matrix of which the retrovirus proteins are then synthesized. Bacteriophages These are viruses that parasitize bacteria. They play an important role in medicine and are widely used in the treatment of purulent diseases caused by staphylococci, etc. Bacteriophages have a complex structure. The genetic material is located in the head of the bacteriophage, which is covered with a protein coat (capsid) on top. In the center of the head is a magnesium atom. Next comes the hollow rod, which goes into the tail threads. Their function is to recognize their own species of bacteria, to attach the phage to the cell. After attachment, the DNA is squeezed out into the bacterial cell, and the membranes remain outside. LECTURE No. 6. The structure and functions of germ cells (gametes) 1. General properties of gametes Compared to other cells, gametes perform unique functions. They ensure the transfer of hereditary information between generations of individuals, which supports life in time. Gametes are one of the directions of differentiation of cells of a multicellular organism, aimed at the process of reproduction. These are highly differentiated cells, the nuclei of which contain all the necessary hereditary information for the development of a new organism. Compared with somatic cells (epithelial, nerve, muscle), gametes have a number of characteristic features. The first difference is the presence of a haploid set of chromosomes in the nucleus, which ensures the reproduction in the zygote of a diploid set typical for organisms of this type (human gametes, for example, contain 23 chromosomes; when gametes merge after fertilization, a zygote is formed that contains 46 chromosomes - a normal number for human cells). The second difference is the unusual nuclear-cytoplasmic ratio (i.e., the ratio of the volume of the nucleus to the volume of the cytoplasm). In eggs, it is reduced due to the fact that there is a lot of cytoplasm, which contains nutrient material (yolk) for the future embryo. In spermatozoa, on the contrary, the nuclear-cytoplasmic ratio is high, since the volume of the cytoplasm is small (almost the entire cell is occupied by the nucleus). This fact is in accordance with the main function of the sperm - the delivery of hereditary material to the egg. The third difference is the low level of metabolism in gametes. Their condition is similar to suspended animation. Male germ cells do not enter mitosis at all, and female gametes acquire this ability only after fertilization (when they already cease to be gametes and become zygotes) or exposure to a factor that induces parthenogenesis. Despite the presence of a number of common features, male and female germ cells differ significantly from each other, due to the difference in the functions performed. 2. The structure and functions of the egg The egg is a large immobile cell that has a supply of nutrients. The size of the female egg is 150-170 microns (much larger than male spermatozoa, whose size is 50-70 microns). The functions of nutrients are different. They are performed: 1) components needed for protein biosynthesis processes (enzymes, ribosomes, m-RNA, t-RNA and their precursors); 2) specific regulatory substances that control all the processes that occur with the egg, for example, the factor of disintegration of the nuclear membrane (prophase 1 of meiotic division begins with this process), the factor that converts the sperm nucleus into a pronucleus before the crushing phase, the factor responsible for the block of meiosis on stages of metaphase II, etc.; 3) the yolk, which includes proteins, phospholipids, various fats, mineral salts. It is he who provides nutrition to the embryo in the embryonic period. According to the amount of yolk in the egg, it can be alecital, i.e. containing a negligible amount of yolk, poly-, meso- or oligolecital. The human egg is alecithal. This is due to the fact that the human embryo very quickly passes from the histiotrophic type of nutrition to the hematotrophic one. Also, the human egg is isolecithal in terms of the distribution of yolk: with a negligible amount of yolk, it is evenly located in the cell, so the nucleus is approximately in the center. The egg has membranes that perform protective functions, prevent the penetration of more than one sperm into the egg, promote the implantation of the embryo into the uterine wall and determine the primary shape of the embryo. The ovum usually has a spherical or slightly elongated shape, contains a set of those typical organelles that any cell does. Like other cells, the egg is delimited by a plasma membrane, but on the outside it is surrounded by a shiny shell consisting of mucopolysaccharides (got its name for its optical properties). The zona pellucida is covered with a radiant crown, or follicular membrane, which is the microvilli of follicular cells. It plays a protective role, nourishes the egg. The egg cell is deprived of the apparatus of active movement. For 4-7 days, it passes through the oviduct to the uterine cavity, a distance that is approximately 10 cm. Plasma segregation is characteristic of the egg. This means that after fertilization in an egg that is not yet crushed, such a uniform distribution of the cytoplasm occurs that in the future the cells of the rudiments of future tissues receive it in a certain regular amount. 3. Structure and functions of spermatozoa A sperm cell is a male reproductive cell (gamete). It has the ability to move, which to a certain extent ensures the possibility of meeting heterosexual gametes. The dimensions of the spermatozoon are microscopic: the length of this cell in humans is 50-70 microns (the largest in a newt is up to 500 microns). All spermatozoa carry a negative electrical charge, which prevents them from sticking together in semen. The number of spermatozoa produced in a male is always colossal. For example, the ejaculate of a healthy male contains about 200 million spermatozoa (a stallion releases about 10 billion spermatozoa). The structure of the sperm In morphology, spermatozoa differ sharply from all other cells, but they contain all the main organelles. Each spermatozoon has a head, neck, intermediate section and tail in the form of a flagellum. Almost the entire head is filled with the nucleus, which carries the hereditary material in the form of chromatin. At the anterior end of the head (at its top) is the acro-soma, which is a modified Golgi complex. Here, the formation of hyaluronidase occurs - an enzyme that is able to break down the mucopolysaccharides of the egg membranes, which makes it possible for the sperm to penetrate into the egg. The mitochondria, which has a helical structure, is located in the neck of the spermatozoon. It is necessary to generate energy, which is spent on the active movement of the sperm towards the egg. The sperm receives most of its energy in the form of fructose, which is very rich in ejaculate. At the border of the head and neck is the centriole. On the transverse section of the flagellum, 9 pairs of microtubules are visible, 2 more pairs are in the center. The flagellum is an organelle of active movement. In the seminal fluid, the male gamete develops a speed equal to 5 cm / h (which, in relation to its size, is about 1,5 times faster than the speed of an Olympic swimmer). Electron microscopy of the spermatozoon revealed that the cytoplasm of the head has not a colloidal, but a liquid-crystalline state. This achieves the resistance of the spermatozoon to adverse environmental conditions (for example, to the acidic environment of the female genital tract). It has been established that spermatozoa are more resistant to the effects of ionizing radiation than immature eggs. The spermatozoa of some animal species have an acrosomal apparatus that ejects a long and thin thread to capture the egg. It has been established that the sperm membrane has specific receptors that recognize the chemicals released by the egg. Therefore, human spermatozoa are capable of directed movement towards the egg (this is called positive chemotaxis). During fertilization, only the head of the spermatozoon, which carries the hereditary apparatus, penetrates into the egg, while the rest of the parts remain outside. 4. Fertilization Fertilization is the process of fusion of germ cells. As a result of fertilization, a diploid cell is formed - a zygote, this is the initial stage in the development of a new organism. Fertilization is preceded by the release of reproductive products, i.e., insemination. There are two types of insemination: 1) outdoor. Sexual products are excreted into the external environment (in many freshwater and marine animals); 2) internal. The male secretes reproductive products into the female genital tract (in mammals, humans). Fertilization consists of three successive stages: convergence of gametes, activation of the egg, fusion of gametes (syngamia), and acrosomal reaction. Convergence of gametes C) due to a combination of factors that increase the likelihood of meeting gametes: sexual activity of males and females, coordinated in time, appropriate sexual behavior, excessive production of spermatozoa, large sizes of eggs. The leading factor is the release of gamons by gametes (specific substances that contribute to the convergence and fusion of germ cells). The egg cell secretes gynogamones, which determine the directed movement of spermatozoa towards it (chemotaxis), and the spermatozoa secrete androgamones. For mammals, the length of stay of gametes in the female genital tract is also important. This is necessary in order for the spermatozoa to acquire a fertilizing ability (the so-called capacitation occurs, that is, the ability for an acrosomal reaction). acrosomal reaction The acrosomal reaction is the release of proteolytic enzymes (mainly hyaluronidase) that are contained in the sperm acrosome. Under their influence, the membranes of the egg are dissolved in the place of the greatest accumulation of spermatozoa. Outside, there is a section of the cytoplasm of the egg (the so-called fertilization tubercle), to which only one of the spermatozoa is attached. After that, the plasma membranes of the egg and sperm merge, a cytoplasmic bridge is formed, and the cytoplasms of both germ cells merge. Further, the nucleus and centriole of the spermatozoon penetrate into the cytoplasm of the egg, and its membrane is embedded in the membrane of the egg. The tail part of the spermatozoon separates and dissolves without playing any significant role in the further development of the embryo. Ovum activation The activation of the egg occurs naturally as a result of its contact with the sperm. There is a cortical reaction that protects the egg from polyspermy, i.e., the penetration of more than one sperm into it. It lies in the fact that detachment and hardening of the yolk membrane occur under the influence of specific enzymes released from the cortical granules. In the egg, the metabolism changes, the need for oxygen increases, and the active synthesis of nutrients begins. The activation of the egg is completed by the beginning of the translational stage of protein biosynthesis (since m-RNA, t-RNA, ribosomes and energy in the form of macroergs were stored back in oogenesis). Fusion of gametes In most mammals, at the time of the meeting of the egg with the sperm cell, it is in metaphase II, since the process of meiosis in it is blocked by a specific factor. In three genera of mammals (horses, dogs, and foxes), the block occurs at the stage of diakinesis. This block is removed only after the nucleus of the sperm enters the egg. While meiosis is being completed in the egg, the nucleus of the sperm that has penetrated into it takes on a different form - first the interphase, and then the prophase nucleus. The sperm nucleus turns into a male pronucleus: the amount of DNA in it doubles, the set of chromosomes in it corresponds to n2c (contains a haploid set of reduplicated chromosomes). After meiosis is completed, the nucleus becomes a female pro-nucleus and also contains an amount of hereditary material corresponding to n2c. Both pronuclei make complex movements within the future zygote, approach and merge, forming a synkaryon (contains a diploid set of chromosomes) with a common metaphase plate. Then a common membrane is formed, a zygote appears. The first mitotic division of the zygote leads to the formation of the first two embryonic cells (blastomeres), each of which carries a diploid set of 2n2c chromosomes. LECTURE No. 7. Asexual reproduction. Forms and biological role Reproduction is a universal property of all living organisms, the ability to reproduce their own kind. With its help, species and life in general are preserved in time. It provides a generational change. The life of the cells that make up an organism is much shorter than the life of the organism itself, so its existence is maintained only by cell reproduction. There are two types of reproduction - asexual and sexual. During asexual reproduction, the main cellular mechanism that provides an increase in the number of cells is mitosis. The parent is one individual. The offspring is an exact genetic copy of the parent material. 1. The biological role of asexual reproduction Maintaining the greatest fitness in little-changing environmental conditions. It reinforces the importance of stabilizing natural selection; provides fast reproduction rates; used in practical selection. Asexual reproduction occurs in both unicellular and multicellular organisms. In unicellular eukaryotes, asexual reproduction is mitotic division, in prokaryotes, nucleoid division, and in multicellular forms, vegetative reproduction. 2. Forms of asexual reproduction In unicellular organisms, the following forms of asexual reproduction are distinguished: division, endogony, schizogony (multiple division) and budding, sporulation. Division is characteristic of such unicellular organisms as amoeba, ciliates, flagellates. First, the mitotic division of the nucleus occurs, then the cytoplasm is divided in half by an ever deeper constriction. In this case, daughter cells receive approximately the same amount of cytoplasm and organelles. Endogony (internal budding) is characteristic of toxoplasma. With the formation of two daughter individuals, the mother gives only two descendants. But there may be internal multiple budding, leading to schizogony. Schizogony develops on the basis of the previous form. It occurs in sporozoans (malarial plasmodium), etc. There is a multiple division of the nucleus without cytokinesis. Then the entire cytoplasm is divided into parts, which are isolated around new nuclei. From one cell, a lot of daughters are formed. Budding (in bacteria, yeast fungi, etc.). At the same time, a small tubercle containing a daughter nucleus (nucleoid) is initially formed on the mother cell. The kidney grows, reaches the size of the mother, and then separates from it. Sporulation (in higher spore plants: mosses, ferns, club mosses, horsetails, algae). The daughter organism develops from specialized cells - spores containing a haploid set of chromosomes. In the bacterial kingdom, sporulation also occurs. Spores, covered with a dense shell that protects it from the adverse effects of the environment, are not a way of reproduction, but a way of experiencing adverse conditions. 3. Vegetative form of reproduction characteristic of multicellular organisms. In this case, a new organism is formed from a group of cells that separate from the parent organism. Plants reproduce by tubers, rhizomes, bulbs, root tubers, root crops, root shoots, layering, cuttings, brood buds, leaves. In animals, vegetative reproduction occurs in the lowest organized forms. In sponges and hydras, it proceeds by budding. Due to the multiplication of a group of cells on the mother's body, a protrusion (kidney) is formed, consisting of cells of the ecto- and endoderm. The kidney gradually increases, tentacles appear on it, and is separated from the mother's body. Ciliary worms are divided into two parts, and in each of them the missing organs are restored due to disordered cell division. Annelids can regenerate an entire organism from a single segment. This type of division underlies regeneration - the restoration of lost tissues and body parts (in annelids, lizards, salamanders). A special form of asexual reproduction is strobilation (in polyps). The polypoid organism grows quite intensively, when it reaches a certain size, it begins to divide into daughter individuals. At this time, it resembles a stack of plates. The resulting jellyfish come off and begin an independent life. LECTURE No. 8. Sexual reproduction. Its forms and biological role 1. The evolutionary meaning of sexual reproduction Sexual reproduction occurs mainly in higher organisms. This is a later type of reproduction (there are about 3 billion years). It provides a significant genetic diversity and, consequently, a large phenotypic variability of the offspring; organisms receive great evolutionary opportunities, material for natural selection arises. In addition to sexual reproduction, there is a sexual process. Its essence is that the exchange of genetic information between individuals occurs, but without an increase in the number of individuals. Meiosis precedes the formation of gametes in multicellular organisms. The sexual process consists in combining hereditary material from two different sources (parents). During sexual reproduction, the offspring are genetically different from their parents, since genetic information is exchanged between the parents. Meiosis is the basis of sexual reproduction. Parents are two individuals - male and female, they produce different sex cells. This manifests sexual dimorphism, which reflects the difference in the tasks performed during sexual reproduction by male and female organisms. Sexual reproduction is carried out through gametes - sex cells that have a haploid set of chromosomes and are produced in parent organisms. The fusion of parental cells leads to the formation of a zygote, from which a descendant organism is subsequently formed. Sex cells are formed in the gonads - the sex glands (in the ovaries in females and the testes in males). The process of formation of germ cells is called gametogenesis (ovogenesis in females and spermatogenesis in males). If male and female gametes are formed in the body of one individual, then it is called hermaphroditic. Hermaphroditism is true (the individual has gonads of both sexes) and false hermaphroditism (the individual has the same type of sex glands - male or female, and the external genitalia and secondary sexual characteristics of both sexes). 2. Types of sexual reproduction In unicellular organisms, two forms of sexual reproduction are distinguished - copulation and conjugation. During conjugation (for example, in ciliates), special germ cells (sexual individuals) are not formed. These organisms have two nuclei - macro- and micronucleus. Usually ciliates reproduce by dividing in two. In this case, the micronucleus first divides mitotically. From it, stationary and migrating nuclei are formed, having a haploid set of chromosomes. Then two cells approach each other, a protoplasmic bridge is formed between them. Through it, the partner of the migrating nucleus moves into the cytoplasm, which then merges with the stationary one. Ordinary micro- and macronuclei are formed, the cells disperse. Since this process does not increase the number of individuals, they speak of a sexual process, and not of sexual reproduction. However, there is an exchange (recombination) of hereditary information, so the offspring are genetically different from their parents. During copulation (in protozoa), the formation of sexual elements and their pairwise fusion occur. In this case, two individuals acquire sexual differences and completely merge, forming a zygote. There is a combination and recombination of hereditary material, so the individuals are genetically different from the parent. 3. Differences between gametes In the process of evolution, the degree of difference between gametes increases. At first, simple isogamy takes place, when germ cells do not yet have differentiation. With further complication of the process, anisogamy occurs: male and female gametes differ, however, not qualitatively, but quantitatively (in chlamydomonas). Finally, in the Volvox algae, the large gamete becomes immobile and the largest of all gametes. This form of anisogamy, when the gametes are sharply different, is called oogamy. In multicellular animals (including humans), only oogamy takes place. Among plants, isogamy and anisogamy are found only in algae. 4. Atypical sexual reproduction We will talk about parthenogenesis, gynogenesis, androgenesis, poly-embryony, double fertilization in angiosperms. Parthenogenesis (virgin reproduction) Daughter organisms develop from unfertilized eggs. Opened in the middle of the XVIII century. Swiss naturalist C. Bonnet. Meaning of parthenogenesis: 1) reproduction is possible with rare contacts of heterosexual individuals; 2) the population size increases sharply, since the offspring, as a rule, are numerous; 3) occurs in populations with high mortality during one season. Types of parthenogenesis: 1) obligate (mandatory) parthenogenesis. It occurs in populations consisting exclusively of females (in the Caucasian rock lizard). At the same time, the probability of meeting heterosexual individuals is minimal (the rocks are separated by deep gorges). Without parthenogenesis, the entire population would be on the brink of extinction; 2) cyclic (seasonal) parthenogenesis (in aphids, daphnia, rotifers). Found in populations that have historically died out in large numbers at certain times of the year. In these species, parthenogenesis is combined with sexual reproduction. At the same time, in the summer, there are only females that lay two types of eggs - large and small. Females appear parthenogenetically from large eggs, and males from small ones, which fertilize the eggs lying at the bottom in winter. Of these, only females appear; 3) facultative (optional) parthenogenesis. It occurs in social insects (wasps, bees, ants). In a population of bees, females (worker bees and queens) emerge from fertilized eggs, and males (drones) from unfertilized eggs. In these species, parthenogenesis exists to regulate the numerical ratio of sexes in the population. There are also natural (exists in natural populations) and artificial (used by humans) parthenogenesis. This type of parthenogenesis was studied by V.N. Tikhomirov. He achieved the development of unfertilized silkworm eggs by irritating them with a thin brush or immersing them in sulfuric acid for a few seconds (it is known that only females give silk thread). Gynogenesis (in bony fish and some amphibians). The sperm enters the egg and only stimulates its development. In this case, the sperm nucleus does not merge with the egg cell nucleus and dies, and the DNA of the egg nucleus serves as a source of hereditary material for the development of the offspring. Androgenesis. The male nucleus introduced into the ovum participates in the development of the embryo, and the nucleus of the ovum dies. The egg cell provides only the nutrients of its cytoplasm. Polyembryony. The zygote (embryo) is divided into several parts asexually, each of which develops into an independent organism. It occurs in insects (riders), armadillos. In armadillos, the cellular material of initially one embryo at the blastula stage is evenly divided between 4-8 embryos, each of which subsequently gives rise to a full-fledged individual. This category of phenomena includes the appearance of identical twins in humans. LECTURE No. 9. The life cycle of a cell. Mitosis 1. The concept of the life cycle The life cycle of a cell reflects all the regular structural and functional changes that occur with the cell over time. The life cycle is the time of the existence of a cell from the moment of its formation by dividing the mother cell to its own division or natural death. In cells of a complex organism (for example, a person), the life cycle of a cell can be different. Highly specialized cells (erythrocytes, nerve cells, striated muscle cells) do not multiply. Their life cycle consists of birth, performance of intended functions, death (heterocalytic interphase). The most important component of the cell cycle is the mitotic (proliferative) cycle. It is a complex of interrelated and coordinated phenomena during cell division, as well as before and after it. The mitotic cycle is a set of processes occurring in a cell from one division to the next and ending with the formation of two cells of the next generation. In addition, the concept of the life cycle also includes the period of performance by the cell of its functions and periods of rest. At this time, the further cell fate is uncertain: the cell may begin to divide (enter mitosis) or begin to prepare to perform specific functions. Mitosis is the main type of somatic eukaryotic cell division. The division process includes several successive phases and is a cycle. Its duration is different and ranges from 10 to 50 hours in most cells. At the same time, in cells of the human body, the duration of mitosis itself is 1-1,5 hours, the 2-period of interphase is 2-3 hours, the S-period of interphase is 6-10 hours . 2. Biological significance of the life cycle Ensures the continuity of genetic material in a number of cells of daughter generations; leads to the formation of cells that are equivalent both in terms of volume and content of genetic information. The main stages of mitosis. 1. Reduplication (self-doubling) of the genetic information of the mother cell and its uniform distribution between the daughter cells. This is accompanied by changes in the structure and morphology of chromosomes, in which more than 90% of the information of a eukaryotic cell is concentrated. 2. The mitotic cycle consists of four consecutive periods: presynthetic (or postmitotic) G1, synthetic S, postsynthetic (or premitotic) G2, and mitosis proper. They constitute the autocatalytic interphase (preparatory period). Phases of the cell cycle: 1) presynthetic (G1). Occurs immediately after cell division. DNA synthesis has not yet taken place. The cell actively grows in size, stores the substances necessary for division: proteins (histones, structural proteins, enzymes), RNA, ATP molecules. There is a division of mitochondria and chloroplasts (i.e., structures capable of autoreproduction). The features of the organization of the interphase cell are restored after the previous division; 2) synthetic (S). Genetic material is duplicated by DNA replication. It occurs in a semi-conservative way, when the double helix of the DNA molecule diverges into two strands and a complementary strand is synthesized on each of them. As a result, two identical DNA double helixes are formed, each of which consists of one new and one old DNA strand. The amount of hereditary material is doubled. In addition, the synthesis of RNA and proteins continues. Also, a small part of mitochondrial DNA undergoes replication (its main part is replicated in the G2 period); 3) postsynthetic (G2). DNA is no longer synthesized, but there is a correction of the shortcomings made during its synthesis in the S period (repair). Energy and nutrients are also accumulated, the synthesis of RNA and proteins (mainly nuclear) continues. S and G2 are directly related to mitosis, so they are sometimes isolated in a separate period - preprophase. This is followed by mitosis itself, which consists of four phases. 3. Mitosis. Characteristics of the main stages Cell division includes two stages - nuclear division (mitosis, or karyokinesis) and cytoplasmic division (cytokinesis). Mitosis consists of four successive phases - prophase, metaphase, anaphase and telophase. It is preceded by a period called interphase (see the characteristics of the mitotic cycle). Phases of mitosis: 1) prophase. The centrioles of the cell center divide and diverge to opposite poles of the cell. From microtubules, a division spindle is formed, which connects the centrios of different poles. At the beginning of prophase, the nucleus and nucleoli are still visible in the cell, by the end of this phase, the nuclear membrane is divided into separate fragments (the nuclear membrane is dismantled), the nucleoli disintegrate. The condensation of chromosomes begins: they twist, thicken, become visible in a light microscope. In the cytoplasm, the number of structures of rough EPS decreases, the number of polysomes sharply decreases; 2) metaphase. The formation of the fission spindle is completed. The condensed chromosomes line up along the equator of the cell, forming the metaphase plate. Spindle microtubules are attached to the centromeres, or kinetochores (primary constrictions), of each chromosome. After that, each chromosome splits longitudinally into two chromatids (daughter chromosomes), which are connected only in the centromere region; 3) anaphase. The connection between the daughter chromosomes is broken, and they begin to move to the opposite poles of the cell at a speed of 0,2-5 µm/min. At the end of anaphase, each pole contains a diploid set of chromosomes. Chromosomes begin to decondense and unwind, become thinner and longer; 4) telophase. Chromosomes are completely despiralized, the structure of the nucleoli and the interphase nucleus is restored, and the nuclear membrane is mounted. The spindle of division is destroyed. Cytokinesis (division of the cytoplasm) occurs. In animal cells, this process begins with the formation of a constriction in the equatorial plane, which becomes deeper and deeper and finally completely divides the mother cell into two daughter cells. With a delay in cytokinesis, multinucleated cells are formed. This is observed during the reproduction of protozoa by schizogony. In multicellular organisms, syncytia are formed in this way - tissues in which there are no boundaries between cells (striated muscle tissue in humans). The duration of each phase depends on the type of tissue, the physiological state of the body, the impact of external factors (light, temperature, chemicals), etc. 4. Atypical forms of mitosis Atypical forms of mitosis include amitosis, endomitosis, and polythenia. 1. Amitosis is a direct division of the nucleus. At the same time, the morphology of the nucleus is preserved, the nucleolus and the nuclear membrane are visible. Chromosomes are not visible, and their uniform distribution does not occur. The nucleus is divided into two relatively equal parts without the formation of a mitotic apparatus (a system of microtubules, centrioles, structured chromosomes). If division ends at the same time, a binuclear cell appears. But sometimes the cytoplasm is also laced. This type of division exists in some differentiated tissues (in cells of skeletal muscles, skin, connective tissue), as well as in pathologically altered tissues. Amitosis never occurs in cells that need to preserve full genetic information - fertilized eggs, cells of a normally developing embryo. This method of division cannot be considered a full-fledged way of reproduction of eukaryotic cells. 2. Endomitosis. In this type of division, after DNA replication, chromosomes do not separate into two daughter chromatids. This leads to an increase in the number of chromosomes in a cell, sometimes by tens of times in comparison with the diploid set. This is how polyploid cells are formed. Normally, this process takes place in intensively functioning tissues, for example, in the liver, where polyploid cells are very common. However, from a genetic point of view, endomitosis is a genomic somatic mutation. 3. Polythenia. There is a multiple increase in the content of DNA (chromonemes) in the chromosomes without an increase in the content of the chromosomes themselves. At the same time, the number of chromonemes can reach 1000 or more, while the chromosomes become gigantic. During polythenia, all phases of the mitotic cycle fall out, except for the reproduction of primary DNA strands. This type of division is observed in some highly specialized tissues (liver cells, cells of the salivary glands of Diptera). The polylithic chromosomes of Drosophila are used to construct cytological maps of genes in chromosomes. LECTURE No. 10. Meiosis: characteristics, biological significance Meiosis is a type of cell division in which the number of chromosomes is halved and cells transition from a diploid to a haploid state. Meiosis is a sequence of two divisions. 1. Stages of meiosis The first division of meiosis (reduction) leads to the formation of haploid cells from diploid cells. In prophase I, as in mitosis, chromosomes spiralize. At the same time, homologous chromosomes approach each other with their identical sections (conjugate), forming bivalents. Before entering meiosis, each chromosome has doubled genetic material and consists of two chromatids, so the bivalent contains 4 strands of DNA. In the process of further spiralization, crossing over can occur - a crossing of homologous chromosomes, accompanied by the exchange of the corresponding sections between their chromatids. In metaphase I, the formation of the division spindle is completed, the threads of which are attached to the centromeres of chromosomes combined into bivalents in such a way that only one thread goes from each centromere to one of the poles of the cell. In anaphase I, the chromosomes move to the poles of the cell, with each pole having a haploid set of chromosomes consisting of two chromatids. In telophase I, the nuclear envelope is restored, after which the mother cell divides into two daughter cells. The second division of meiosis begins immediately after the first and is similar to mitosis, but the cells entering it carry a haploid set of chromosomes. Prophase II is very short in time. It is followed by metaphase II, while the chromosomes are located in the equatorial plane, a division spindle is formed. In anaphase II, the centromeres separate, and each chromatid becomes an independent chromosome. Daughter chromosomes separated from each other are sent to the division poles. In telophase II, cell division occurs, in which 4 daughter haploid cells are formed from two haploid cells. Thus, as a result of meiosis, four cells with a haploid set of chromosomes are formed from one diploid cell. During meiosis, two mechanisms of recombination of genetic material are carried out. 1. Intermittent (crossing over) is an exchange of homologous regions between chromosomes. Occurs in prophase I at the stage of pachytene. The result is the recombination of allelic genes. 2. Constant - random and independent divergence of homologous chromosomes in anaphase I of meiosis. As a result, gametes receive a different number of chromosomes of paternal and maternal origin. 2. Biological significance of meiosis 1) is the main stage of gametogenesis; 2) ensures the transfer of genetic information from organism to organism during sexual reproduction; 3) daughter cells are not genetically identical to the parent and to each other. LECTURE No. 11. Gametogenesis 1. Concepts of gametogenesis Gametogenesis is the process of formation of germ cells. It flows in the sex glands - gonads (in the ovaries in females and in the testes in males). Gametogenesis in the body of a female is reduced to the formation of female germ cells (eggs) and is called oogenesis. In males, male sex cells (spermatozoa) appear, the process of formation of which is called spermatogenesis. Gametogenesis is a sequential process, which consists of several stages - reproduction, growth, maturation of cells. The process of spermatogenesis also includes a formation stage, which is not present in oogenesis. 2. Stages of gametogenesis 1. Stage of reproduction. The cells from which male and female gametes are subsequently formed are called spermatogonia and ovogonia, respectively. They carry a diploid set of 2n2c chromosomes. At this stage, the primary germ cells repeatedly divide by mitosis, as a result of which their number increases significantly. Spermatogonia multiply throughout the reproductive period in the male body. Reproduction of oogonia occurs mainly in the embryonic period. In humans, in the ovaries of the female body, the process of reproduction of oogonia most intensively occurs between 2 and 5 months of intrauterine development. By the end of the 7th month, most of the oocytes enter prophase I of meiosis. If in a single haploid set the number of chromosomes is denoted as n, and the amount of DNA as c, then the genetic formula of cells in the reproduction stage corresponds to 2n2c before the synthetic period of mitosis (when DNA replication occurs) and 2n4c after it. 2. Stage of growth. The cells increase in size and turn into spermatocytes and oocytes of the first order (the latter reach especially large sizes due to the accumulation of nutrients in the form of yolk and protein granules). This stage corresponds to interphase I of meiosis. An important event of this period is the replication of DNA molecules with a constant number of chromosomes. They acquire a double-stranded structure: the genetic formula of cells during this period looks like 2n4c. 3. Stage of maturation. Two consecutive divisions occur - reduction (meiosis I) and equational (meiosis II), which together constitute meiosis. After the first division (meiosis I), spermatocytes and oocytes of the second order (with the genetic formula n2c) are formed, after the second division (meiosis II) - spermatids and mature eggs (with the formula nc) with three reduction bodies that die and are not involved in the reproduction process . This preserves the maximum amount of yolk in the eggs. Thus, as a result of the maturation stage, one spermatocyte of the 2st order (with the formula 4n2c) produces four spermatids (with the formula nc), and one oocyte of the 4st order (with the formula XNUMXnXNUMXc) forms one mature egg (with the formula nc) and three reduction bodies . 4. Stage of formation, or spermiogenesis (only during spermatogenesis). As a result of this process, each immature spermatid turns into a mature spermatozoon (with the formula nc), acquiring all the structures that are characteristic of it. The spermatid nucleus thickens, supercoiling of chromosomes occurs, which become functionally inert. The Golgi complex moves to one of the poles of the nucleus, forming the acrosome. Centrioles rush to the other pole of the nucleus, and one of them takes part in the formation of the flagellum. A single mitochondrion spirals around the flagellum. Almost the entire cytoplasm of the spermatid is rejected, so the sperm head contains almost no cytoplasm. LECTURE No. 12. Ontogeny 1. The concept of ontogenesis Ontogeny is the process of individual development of an individual from the moment a zygote is formed during sexual reproduction (or the appearance of a daughter individual during asexual reproduction) until the end of life. The periodization of ontogeny is based on the possibility of sexual reproduction by an individual. According to this principle, ontogenesis is divided into three periods: pre-reproductive, reproductive and post-reproductive. The pre-reproductive period is characterized by the inability of an individual to sexual reproduction, due to its immaturity. During this period, the main anatomical and physiological transformations take place, forming a sexually mature organism. In the pre-reproductive period, the individual is most vulnerable to the adverse effects of physical, chemical and biological environmental factors. This period, in turn, is divided into 4 periods: embryonic, larval, metamorphosis period and juvenile. The embryonic (embryonic) period lasts from the moment of fertilization of the egg to the release of the embryo from the egg membranes. The larval period occurs in some representatives of the lower vertebrates, the embryos of which, having emerged from the egg membranes, exist for some time, not having all the features of a mature individual. The larva is characterized by the embryonic features of the individual, the presence of temporary auxiliary organs, the ability to actively feed and reproduce. Due to this, the larva completes its development in the most favorable conditions for this. Metamorphosis as a period of ontogenesis is characterized by structural transformations of the individual. In this case, the auxiliary organs are destroyed, and the permanent organs are improved or newly formed. The juvenile period lasts from the end of metamorphosis to the entry into the reproductive period. During this period, the individual grows intensively, the final formation of the structure and function of organs and systems occurs. In the reproductive period, the individual realizes its ability to reproduce. During this period of development, it is finally formed and resistant to the action of adverse external factors. The post-reproductive period is associated with progressive aging of the body. It is characterized by a decrease, and then the complete disappearance of the function of reproduction, reverse structural and functional changes in the organs and systems of the body. Reduced resistance to various adverse effects. Postembryonic development can be direct or indirect. With direct (without a larva) development, an organism similar to an adult emerges from the egg membranes or from the mother's body. Postembryonic development of these animals is reduced mainly to growth and puberty. Direct development occurs in animals that breed by laying eggs when the eggs are rich in yolk (invertebrates, fish, reptiles, birds, some mammals), and in viviparous forms. In the latter case, the eggs are almost devoid of yolk. The embryo develops inside the maternal organism, and its vital activity is provided by the placenta (placental mammals and humans). Indirect development - larval, with metamorphosis. Metamorphosis can be incomplete, when the larva resembles an adult organism and becomes more and more similar to it with each new molt, and complete, when the larva differs from the adult organism in many of the most important features of the external and internal structure, and there is a pupal stage in the life cycle. 2. Embryonic development The period of embryonic development is most complex in higher animals and consists of several stages. The first stage of embryonic development is crushing. At the same time, first 2 cells are formed from the zygote by mitotic division, then 4, 8, etc. The resulting cells are called blastomeres, and the embryo at this stage of development is called the blastula. At the same time, the total mass and volume almost do not increase, and new cells become smaller and smaller. Mitotic divisions occur rapidly one after another, characterized by a shortening and sometimes by the loss of some stages of mitosis. Thus, this process is characterized by much faster DNA replication. Stage G1 (preparation for DNA synthesis and cell growth) falls out. Stage G2 is significantly shortened. This rapid succession of mitotic divisions is provided by the energy and nutrients of the cytoplasm of the egg. Sometimes the resulting blastula is a cavity formation in which the blastomeres are arranged in one layer, limiting the cavity - the blastocoel. In cases where the blastula looks like a dense ball without a cavity in the center, it is called a morula (morum - mulberry). The next stage of embryonic development is gastrulation. At this time, the blastomeres, which continue to divide rapidly, acquire motor activity and move relative to each other, forming layers of cells - germ layers. Gastrulation can occur either by invagination (invagination) of one of the walls of the blastula into the cavity of the blastocoel, immigration of individual cells, epiboly (fouling), or delamination (splitting into two plates). As a result, the outer germ layer is formed - the ectoderm, and the inner one - the endoderm. In most multicellular animals (except for sponges and coelenterates), a third, middle germ layer, the mesoderm, is formed between them, formed from cells lying on the border between the outer and inner sheets. Then comes the stage of histo- and organogenesis. In this case, the rudiment of the nervous system, the neurula, is first formed. This occurs by isolating a group of ectoderm cells on the dorsal side of the embryo in the form of a plate, which folds into a groove, and then into a long tube and goes deep into, under the layer of ectoderm cells. After that, the rudiment of the brain and sensory organs is formed on the front of the tube, and the rudiment of the spinal cord and peripheral nervous system is formed from the main part of the tube. In addition, the skin and its derivatives develop from the ectoderm. The endoderm gives rise to the organs of the respiratory and digestive systems. Muscle, cartilaginous and bone tissue, organs of the circulatory and excretory systems are formed from the mesoderm. LECTURE No. 13. Laws of inheritance 1. Laws of G. Mendel Inheritance is the process of passing on genetic information over a number of generations. Inherited traits can be qualitative (monogenic) and quantitative (polygenic). Qualitative traits are represented in the population, as a rule, by a small number of mutually exclusive options. For example, yellow or green pea seeds, gray or black body color in fruit flies, light or dark eye color in humans, normal blood clotting, or hemophilia. Qualitative traits are inherited according to the laws of Mendel (Mendelian traits). Quantitative traits are represented in the population by a variety of alternative options. Quantitative traits include such traits as growth, skin pigmentation, mental ability in humans, egg production in chickens, sugar content in sugar beet roots, etc. The inheritance of polygenic traits in general does not obey Mendel's laws. Depending on the localization of the gene in the chromosome and the interaction of allelic genes, several variants of monogenic inheritance of traits are distinguished. 1. Autosomal type of inheritance. There are dominant, recessive and co-dominant autosomal inheritance patterns. 2. Sex-linked (sex) type of inheritance. There are X-linked (dominant or recessive) inheritance and Y-linked inheritance. Mendel studied the inheritance of color in pea seeds by crossing plants with yellow and green seeds, and based on his observations he formulated patterns that were later named after him. Mendel's first law The law of uniformity of hybrids of the first generation, or the law of dominance. According to this law, with monohybrid crossing of individuals homozygous for alternative traits, the offspring of the first hybrid generation is uniform in genotype and phenotype. Mendel's second law splitting law. It states: after crossing the F1 offspring of two homozygous parents in the F2 generation, a splitting of the offspring according to the phenotype was observed in the ratio of 3: 1 in the case of complete dominance and 1: 2: 1 in case of incomplete dominance. The techniques used by Mendel formed the basis of a new method for studying inheritance - hybridological. Hybridological analysis is the formulation of a system of crosses that makes it possible to identify patterns of inheritance of traits. Conditions for conducting hybridological analysis: 1) parental individuals must be of the same species and reproduce sexually (otherwise crossing is simply impossible); 2) parental individuals must be homozygous for the studied traits; 3) parental individuals must differ in the studied characteristics; 4) the parents are crossed with each other once to obtain first generation F1 hybrids, which are then crossed with each other to obtain second generation F2 hybrids; 5) it is necessary to carry out a strict accounting of the number of individuals of the first and second generations that have the trait under study. 2. Di- and polyhybrid crossing. Independent Inheritance Dihybrid crossing is the crossing of parental individuals that differ in two pairs of alternative traits and, accordingly, in two pairs of allelic genes. Polyhybrid crossing is the crossing of individuals that differ in several pairs of alternative traits and, accordingly, in several pairs of allelic genes. Georg Mendel crossed pea plants that differed in seed color (yellow and green) and in the nature of the seed surface (smooth and wrinkled). Crossing pure lines of peas with yellow smooth seeds with clean lines having green wrinkled seeds, he obtained hybrids of the first generation with yellow smooth seeds (dominant traits). Then Mendel crossed the hybrids of the first generation with each other and received four phenotypic classes in a ratio of 9: 3: 3: 1, i.e., as a result, two new combinations of characters appeared in the second generation: yellow wrinkled and green smooth. For each pair of traits, a 3:1 ratio was noted, characteristic of monohybrid crossing: in the second generation, 3/4 smooth and 1/4 wrinkled seeds and 3/4 yellow and 1/4 green seeds were obtained. Consequently, two pairs of traits are combined in hybrids of the first generation, and then separated and become independent of each other. Based on these observations, Mendel's third law was formulated. Mendel's third law Law of independent inheritance: splitting for each pair of traits proceeds independently of other pairs of traits. In its pure form, this law is valid only for genes located on different chromosomes, and is partially observed for genes located on the same chromosome, but at a considerable distance from each other. Mendel's experiments formed the basis of a new science - genetics. Genetics is the science that studies heredity and variation. The following conditions contributed to the success of Mendel's research: 1. A good choice of the object of study - peas. When Mendel was asked to repeat his observations on the bink hawk, that ubiquitous weed, he was unable to do so. 2. Analysis of the inheritance of individual pairs of traits in the offspring of crossed plants that differ in one, two or three pairs of alternative traits. Records were kept separately for each pair of these traits after each crossing. 3. Mendel not only recorded the results obtained, but also carried out their mathematical analysis. Mendel also formulated the law of gamete purity, according to which the gamete is pure from the second allelic gene (alternative trait), that is, the gene is discrete and does not mix with other genes. In monohybrid crossing, in the case of complete dominance in heterozygous hybrids of the first generation, only the dominant allele appears, but the recessive allele is not lost and does not mix with the dominant one. Among hybrids of the second generation, both the recessive and the dominant allele can appear in its pure form, i.e., in the homozygous state. As a result, the gametes formed by such a heterozygote are pure, i.e. gamete A does not contain anything from the allele a, gamete a is pure from A. At the cellular level, the basis of the discreteness of alleles is their localization in different chromosomes of each homologous pair, and the discreteness of genes is their location in different loci of chromosomes. 3. Interactions of allelic genes In the interaction of allelic genes, different variants of the manifestation of a trait are possible. If the alleles are in the homozygous state, then the trait variant corresponding to the allele develops. In the case of heterozygosity, the development of a trait will depend on the specific type of interaction of allelic genes. Complete dominance This is a type of interaction of allelic genes, in which the manifestation of one of the alleles (A) does not depend on the presence of another allele (A1) in the genotype of an individual, and AA1 heterozygotes do not phenotypically differ from homozygotes for this allele (AA). In the heterozygous AA1 genotype, the A allele is dominant. The presence of the A1 allele does not manifest itself phenotypically in any way, therefore it acts as a recessive one. Incomplete dominance It is noted in cases where the phenotype of CC1 heterozygotes differs from the phenotype of CC and C1C1 homozygotes by an intermediate degree of manifestation of the trait, i.e., the allele responsible for the formation of a normal trait, being in a double dose in a CC homozygote, manifests itself more strongly than in a single dose in a CC1 heterozygote . The possible genotypes in this case differ in expressivity, i.e., the degree of expression of the trait. Codominating This is a type of interaction of allelic genes, in which each of the alleles has its own effect. As a result, an intermediate variant of the trait is formed, new in comparison with the variants formed by each allele separately. Interallelic complementation This is a rare type of interaction of allelic genes, in which an organism heterozygous for two mutant alleles of the M gene (M1M11) can form a normal M trait. For example, the M gene is responsible for the synthesis of a protein that has a quaternary structure and consists of several identical polypeptide chains. The mutant M1 allele causes the synthesis of the altered M1 peptide, and the mutant M11 allele determines the synthesis of another, but also abnormal, polypeptide chain. The interaction of such altered peptides and the compensation of altered regions during the formation of the quaternary structure can, in rare cases, lead to the appearance of a protein with normal properties. 4. Inheritance of blood groups of the ABO system The inheritance of blood groups of the ABO system in humans has some features. The formation of I, II and III blood groups occurs according to this type of interaction of allelic genes as dominance. Genotypes containing the IA allele in the homozygous state, or in combination with the IO allele, determine the formation of the second (A) blood type in a person. The same principle underlies the formation of the third (B) blood type, i.e., the IA and IB alleles act as dominant in relation to the IO allele, which in the homozygous state forms the first (O) blood type IOIO. The formation of the fourth (AB) blood group follows the path of codominance. The IA and IB alleles, which separately form the second and third blood groups, respectively, determine the IAIB (fourth) blood group in the heterozygous state. LECTURE No. 14. Heredity 1. Non-allelic genes Non-allelic genes are genes located in different parts of the chromosomes and encoding different proteins. Non-allelic genes can also interact with each other. In this case, either one gene determines the development of several traits, or, conversely, one trait is manifested under the action of a combination of several genes. There are three forms of interaction of non-allelic genes: 1) complementarity; 2) epistasis; 3) polymer. Complementary (additional) action of genes is a type of interaction of non-allelic genes, the dominant alleles of which, when combined in the genotype, determine a new phenotypic manifestation of traits. In this case, the splitting of F2 hybrids according to the phenotype can occur in ratios of 9: 6: 1, 9: 3: 4, 9: 7, sometimes 9: 3: 3: 1. An example of complementarity is the inheritance of the shape of a pumpkin fruit. The presence of dominant genes A or B in the genotype determines the spherical shape of the fruit, and recessive genes - elongated. If there are simultaneously dominant genes A and B in the genotype, the shape of the fetus will be disc-shaped. When crossing pure lines with varieties that have a spherical fruit shape, in the first hybrid generation F1, all fruits will have a disc-shaped shape, and in the F2 generation, splitting by phenotype will occur: out of every 16 plants, 9 will have disc-shaped fruits, 6 - spherical and 1 - elongated. Epistasis - the interaction of non-allelic genes, in which one of them is suppressed by the other. The repressive gene is called epistatic, the repressed gene is called hypostatic. If the epistatic gene does not have its own phenotypic manifestation, then it is called an inhibitor and is denoted by the letter I. The epistatic interaction of non-allelic genes can be dominant and recessive. In dominant epistasis, the expression of the hypostatic gene (B, b) is suppressed by the dominant epistatic gene (I > B, b). Phenotypic segregation in dominant epistasis can occur in a ratio of 12:3:1, 13:3, 7:6:3. Recessive epistasis is the suppression by the recessive allele of the epistatic gene of the alleles of the hypostatic gene (i > B, b). Splitting by phenotype can go in a ratio of 9: 3: 4, 9: 7, 13: 3. Polymeria - the interaction of non-allelic multiple genes that uniquely affect the development of the same trait; the degree of manifestation of a trait depends on the number of genes. Polymeric genes are denoted by the same letters, and alleles of the same locus have the same subscript. The polymer interaction of non-allelic genes can be cumulative and non-cumulative. With cumulative (accumulative) polymerization, the degree of manifestation of a trait depends on the summing effect of genes. The more dominant alleles of genes, the more pronounced this or that trait. F2 cleavage by phenotype occurs in a ratio of 1:4:6:4:1. With non-cumulative polymerism, the trait manifests itself in the presence of at least one of the dominant alleles of polymeric genes. The number of dominant alleles does not affect the severity of the trait. Phenotypic cleavage occurs at a ratio of 15:1. 2. Genetics of sex Inheritance of sex-linked traits The sex of an organism is a set of signs and anatomical structures that provide sexual reproduction and the transmission of hereditary information. In determining the sex of a future individual, the chromosomal apparatus of the zygote, the karyotype, plays a leading role. There are chromosomes that are the same for both sexes - autosomes, and sex chromosomes. The human karyotype contains 44 autosomes and 2 sex chromosomes - X and Y. Two X chromosomes are responsible for the development of the female sex in humans, that is, the female sex is homogametic. The development of the male sex is determined by the presence of X- and Y-chromosomes, that is, the male sex is heterogametic. Sex-linked traits These are signs that are encoded by genes located on the sex chromosomes. In humans, traits encoded by the X chromosome genes can occur in both sexes, while those encoded by the Y chromosome genes can only occur in men. It should be borne in mind that in the male genotype there is only one X chromosome, which almost does not contain regions homologous to the Y chromosome, therefore all genes localized in the X chromosome, including recessive ones, appear in the phenotype in the first generation. The sex chromosomes contain genes that regulate the manifestation of not only sexual characteristics. The X chromosome has genes responsible for blood clotting, color perception, and the synthesis of a number of enzymes. The Y chromosome contains a number of genes that control traits inherited through the male line (hollandric traits): ear hairiness, the presence of a skin membrane between the fingers, etc. Very few genes are known that are common to X and Y chromosomes. There are X-linked and Y-linked (Holandric) inheritance. X-linked inheritance Since the X chromosome is present in the karyotype of each person, the traits inherited linked to the X chromosome appear in both sexes. Females receive these genes from both parents and pass them on to their offspring through their gametes. Males receive the X chromosome from their mother and pass it on to their female offspring. There are X-linked dominant and X-linked recessive inheritance. In humans, an X-linked dominant trait is passed on by the mother to all offspring. A man passes on his X-linked dominant trait only to his daughters. An X-linked recessive trait in women appears only when they receive the corresponding allele from both parents. In men, it develops when receiving a recessive allele from the mother. Women pass the recessive allele to their offspring of both sexes, while men only pass it on to their daughters. With X-linked inheritance, an intermediate character of the manifestation of the trait in heterozygotes is possible. Y-linked genes are present in the male genotype only and are passed down from generation to generation from father to son. LECTURE No. 15. Heredity and variability 1. Types of variability Variability is a property of living organisms to exist in various forms (options). Types of variability Distinguish between hereditary and non-hereditary variability. Hereditary (genotypic) variability is associated with a change in the genetic material itself. Non-hereditary (phenotypic, modification) variability is the ability of organisms to change their phenotype under the influence of various factors. Modification variability is caused by changes in the organism's external environment or its internal environment. reaction rate These are the boundaries of the phenotypic variability of a trait that occurs under the influence of environmental factors. The reaction rate is determined by the genes of the organism, so the reaction rate for the same trait is different for different individuals. The range of the reaction rate of various signs also varies. Those organisms in which the reaction rate is wider for this trait have higher adaptive capabilities under certain environmental conditions, i.e., modification variability in most cases is adaptive in nature, and most of the changes that occur in the body when exposed to certain environmental factors are useful. However, phenotypic changes sometimes lose their adaptive character. If the phenotypic variability is clinically similar to a hereditary disease, then such changes are called phenocopy. Combination variability Associated with a new combination of unchanged parental genes in the genotypes of the offspring. Factors of combinative variability. 1. Independent and random segregation of homologous chromosomes in anaphase I of meiosis. 2. Crossing over. 3. Random combination of gametes during fertilization. 4. Random selection of parental organisms. Mutations These are rare, random, persistent changes in the genotype that affect the entire genome, entire chromosomes, parts of chromosomes, or individual genes. They arise under the influence of mutagenic factors of physical, chemical or biological origin. Mutations are: 1) spontaneous and induced; 2) harmful, useful and neutral; 3) somatic and generative; 4) gene, chromosomal and genomic. Spontaneous mutations are mutations that have arisen undirectedly, under the influence of an unknown mutagen. Induced mutations are mutations caused artificially by the action of a known mutagen. Chromosomal mutations are changes in the structure of chromosomes during cell division. There are the following types of chromosomal mutations. 1. Duplication - doubling of a section of a chromosome due to unequal crossing over. 2. Deletion - loss of a section of a chromosome. 3. Inversion - rotation of a chromosome segment by 180 °. 4. Translocation - moving a section of a chromosome to another chromosome. Genomic mutations are changes in the number of chromosomes. Types of genomic mutations. 1. Polyploidy - a change in the number of haploid sets of chromosomes in a karyotype. Under the karyotype understand the number, shape and number of chromosomes characteristic of a given species. There are nullosomy (the absence of two homologous chromosomes), monosomy (the absence of one of the homologous chromosomes) and polysomy (the presence of two or more extra chromosomes). 2. Heteroploidy - a change in the number of individual chromosomes in the karyotype Gene mutations are the most common. Causes of gene mutations: 1) nucleotide dropout; 2) insertion of an extra nucleotide (this and the previous reasons lead to a shift in the reading frame); 3) replacement of one nucleotide by another. 2. Linkage of genes and crossing over Genes localized in the same chromosome form a linkage group and are inherited, as a rule, together. The number of linkage groups in diploid organisms is equal to the haploid set of chromosomes. Women have 23 clutch groups, men have 24. The linkage of genes located on the same chromosome can be complete or incomplete. Complete linkage of genes, i.e., joint inheritance, is possible in the absence of the process of crossing-belief. This is typical for genes of sex chromosomes, organisms heterogametic for sex chromosomes (XY, XO), as well as for genes located near the centromere of the chromosome, where crossing over almost never occurs. In most cases, the genes localized in one chromosome are not fully linked, and in prophase I of meiosis, identical sections are exchanged between homologous chromosomes. As a result of crossing-over, allelic genes that were in the composition of the clutch groups of the parental individuals are separated and form new combinations that fall into gametes. Gene recombination occurs. Gametes and zygotes containing recombinations of linked genes are called crossover. Knowing the number of crossover gametes and the total number of gametes of a given individual, it is possible to calculate the frequency of crossing over as a percentage using the formula: the ratio of the number of crossover gametes (individuals) to the total number of gametes (individuals) multiplied by 100%. The percentage of crossing over between two genes can be used to determine the distance between them. For a unit of distance between genes - a morganide - 1% of crossing over is conventionally accepted. Crossover frequency also indicates the strength of linkage between genes. The linkage strength between two genes is equal to the difference between 100% and the percentage of crossover between these genes. The genetic map of a chromosome is a diagram of the mutual arrangement of genes that are in the same linkage group. Determination of linkage groups and distances between genes is not the final step in constructing a genetic map of a chromosome, since it is also necessary to establish the correspondence of the studied linkage group to a specific chromosome. The determination of the linkage group is carried out by the hybridological method, i.e., by studying the results of crossing, and the study of chromosomes is carried out by the cytological method with microscopic examination of preparations. To determine the correspondence of a given linkage group to a specific chromosome, chromosomes with a modified structure are used. A standard dihybrid crossing analysis is performed, in which one trait under study is encoded by a gene located on a chromosome with an altered structure, and the second is encoded by a gene located on any other chromosome. If there is a linked inheritance of these two traits, we can talk about the connection of this chromosome with a certain linkage group. Analysis of genetic and cytological maps made it possible to formulate the main provisions of the chromosome theory of heredity. 1. Each gene has a specific permanent location (locus) on the chromosome. 2. Genes in chromosomes are located in a certain linear sequence. 3. The frequency of crossing over between genes is directly proportional to the distance between them and inversely proportional to the linkage strength. 3. Methods for studying human heredity Genealogical method The genealogical method, or the method of analyzing pedigrees, includes the following steps: 1. Collecting information from the proband about the presence or absence of the analyzed trait (often a disease) in his relatives and compiling a legend about each of them (a verbal description). For a more accurate result, it is necessary to collect information about relatives in three or four generations. 2. Graphic representation of the pedigree using symbols. Each relative of the proband receives his own code. 3. Analysis of the pedigree, solving the following tasks: 1) determination of the group of diseases to which the studied disease belongs (hereditary, multifactorial or a group of phenocopies); 2) determination of the type and variant of inheritance; 3) determination of the probability of manifestation of the disease in the pro-gang and other relatives. Cytogenetic methods Cytological methods are associated with staining of cytological material and subsequent microscopy. They allow you to determine violations of the structure and number of chromosomes. This group of methods includes: 1) a method for determining the X-chromatin of interphase chromosomes by staining with non-fluorescent or fluorescent dyes; 2) a method for determining the Y-chromatin of interphase chromosomes by staining with fluorescent dyes; 3) a routine method for staining metaphase chromosomes to determine the number and group membership of chromosomes, identify 1, 2, 3, 9, 16 chromosomes and the Y-chromosome; 4) method of differential staining of metaphase chromosomes for identification of all chromosomes according to the features of transverse striation. In this method, lymphocytes, fibroblasts, bone marrow cells, germ cells, and hair follicle cells are most often used for microscopy. Biochemical methods This group includes methods used mainly in the differential diagnosis of hereditary metabolic disorders with a known defect in the primary biochemical product of a given gene. All biochemical methods are divided into qualitative, quantitative and semi-quantitative. For research, blood, urine or amniotic fluid are taken. Qualitative methods are simpler, less expensive and less time-consuming, therefore they are used for mass screening (for example, testing newborns in the maternity hospital for phenylketonuria). Quantitative methods are more accurate, but also more time-consuming and expensive. Therefore, they are used only for special indications and in cases where screening, carried out by qualitative methods, gave a positive result. Indications for the use of biochemical methods: 1) mental retardation of unclear etiology; 2) decreased vision and hearing; 3) intolerance to certain foods; 4) convulsive syndrome, increased or decreased muscle tone. DNA diagnostics This is the most accurate method for diagnosing monogenic hereditary diseases. Advantages of the method: 1) allows you to determine the cause of the disease at the genetic level; 2) reveals minimal violations of the DNA structure; 3) minimally invasive; 4) does not require repetition. The method is based on increasing copies of DNA fragments in various ways. twin method It is mainly used to determine the relative role of heredity and environmental factors in the occurrence of a disease. At the same time, monozygotic and dizygotic twins are studied. LECTURE No. 16. Structure and functions of the biosphere 1. The concept of the noosphere. Human impact on the biosphere The foundations of the doctrine of the biosphere were developed by the Russian scientist V. I. Vernadsky. The biosphere is the shell of the Earth inhabited by living organisms, including part of the lithosphere, hydrosphere and part of the atmosphere. The atmosphere as part of the biosphere is a layer 2-3 to 10 km thick (for spores of fungi and bacteria) above the Earth's surface. The limiting factor for the spread of living organisms in the atmosphere is the distribution of oxygen and the level of ultraviolet radiation. There are no microorganisms for which air would be the main habitat. They are introduced into the atmosphere from soil, water, etc. The lithosphere is inhabited by living organisms to a considerable depth, but their greatest number is concentrated in the surface layer of the soil. The amount of oxygen, light, pressure and temperature limit the spread of living organisms. The hydrosphere is inhabited by living beings to a depth of more than 11 m. Hydrobionts live in both fresh and salt water and are divided into 3 groups according to their habitat: 1) plankton - organisms living on the surface of water bodies and passively moving due to the movement of water; 2) nekton - actively moving in the water column; 3) benthos - organisms that live at the bottom of water bodies or burrow into silt. The limiting factor is light (for plants). The circulation of substances in nature between living and non-living matter is one of the most characteristic features of the biosphere. The biological cycle is the biogenic migration of atoms from the environment into organisms and from organisms into the environment. Biomass also performs other functions: 1) gas - constant gas exchange with the external environment due to the respiration of living organisms and plant photosynthesis; 2) concentration - constant biogenic migration of atoms into living organisms, and after their death - into inanimate nature; 3) redox - exchange of matter and energy with the external environment. During dissimilation, organic substances are oxidized; during assimilation, the energy of ATP is used; 4) biochemical - chemical transformations of substances that form the basis of the life of the organism. The term "noosphere" was introduced by V. I. Vernadsky at the beginning of the XNUMXth century. Initially, the noosphere was presented as a "thinking shell of the Earth" (from Gr. noqs - "mind"). At present, the noosphere is understood as the biosphere transformed by human labor and scientific thought. Ideally, the noosphere implies a new stage in the development of the biosphere, which is based on a reasonable regulation of the relationship between man and nature. However, at the moment, a person affects the biosphere in most cases, it is detrimental. Unreasonable human economic activity has led to the emergence of global problems, including: 1) change in the state of the atmosphere in the form of the appearance of the greenhouse effect and the ozone crisis; 2) decrease in the area of the Earth occupied by forests; 3) desertification of lands; 4) decrease in species diversity; 5) pollution of ocean and fresh waters, as well as land by industrial and agricultural waste; 6) continuous population growth. 2. Parasitism as an ecological phenomenon Parasitism is a universal, widespread phenomenon in wildlife, consisting in the use of one organism by another as a source of food. In this case, the parasite harms the host up to death. Pathways to parasitism. 1. The transition of free-living forms (predators) to ectoparasitism with an increase in the time of possible existence without food and the time of contact with the prey. 2. The transition from commensalism (meal, parasitism, a situation where the host serves only as a habitat) to endo-parasitism in the case of commensals using not only waste, but part of the host's diet and even its tissues. 3. Primary endoparasitism as a result of accidental, often repeated introduction of parasite eggs and cysts into the digestive system of the host. Features of the habitat of parasites. 1. Constant and favorable level of temperature and humidity. 2. Abundance of food. 3. Protection from adverse factors. 4. Aggressive chemical composition of the habitat (digestive juices). characteristics of parasites. 1. The presence of two habitats: the first order environment - the host organism, the second order environment - the external environment. 2. The parasite has a smaller body size and a shorter life span compared to the host. 3. Parasites are distinguished by a high ability to reproduce, due to the abundance of food. 4. The number of parasites in the host organism can be very high. 5. Parasitic way of life is their specific feature. Classification of parasites Depending on the time spent on the host, parasites can be permanent, if they never occur in a free-living state (lice, scabies, malarial plasmodium), and temporary, if associated with the host only during meals (mosquitoes, bedbugs, fleas). According to the obligatory parasitic lifestyle, parasites are obligate, if the parasitic lifestyle is their indispensable species feature (for example, helminths), and facultative, capable of leading a non-parasitic lifestyle (many plant parasites). According to the place of residence on the host, parasites are divided into ectoparasites living on the surface of the host's body (human lice, mosquitoes, mosquitoes, horseflies), intradermal parasites living in the thickness of the host's skin (scabies), cavitary parasites living in the cavities of various organs of the host, communicating with the external environment (bovine and porcine tapeworms) and actually endoparasites living in the internal organs of the host organism, cells and blood plasma (echinococcus, trichinella, malarial plasmodium). In the wild, parasites regulate the abundance of individuals in host populations. Features of the vital activity of parasites The life cycle of parasites can be simple or complex. A simple cycle of development occurs without the participation of an intermediate host; it is typical for ectoparasites, protozoa, and some geohelminths. A complex life cycle is characteristic of parasites that have at least one intermediate host (broad tapeworm). The parasite spreads throughout its life. The inactive resting stage of development ensures the continuation of the existence of the parasite in time, while the active mobile stage ensures expansion in space. In general, a host is a creature whose organism is a temporary or permanent habitat and food source for the parasite. The same host species can be a habitat and food source for several species of parasites. Parasites are characterized by a change of hosts associated with reproduction or with the development of the parasite. Many parasites have multiple hosts. The definitive (definitive) host is the species in which the parasite is in its adult state and reproduces sexually. There can be one or more intermediate hosts. These are species in which the parasite is at the larval stage of development, and if it reproduces, then, as a rule, asexually. A reservoir host is a host in which the parasite survives and where the parasite accumulates. Man is an ideal host for the parasite, because: 1) man is represented by numerous, ubiquitous populations; 2) a person constantly comes into contact with natural foci of diseases of wild animals; 3) a person often lives in conditions of overpopulation, which facilitates the transmission of the parasite; 4) a person is in contact with many types of animals; 5) man is omnivorous. Mechanisms of transmission of the parasite: fecal-oral, airborne, transmissible, contagious. The most common parasites in humans are a variety of helminth worms that cause diseases of the helminthiasis group. There are bio-, geohelminthiases and contact helminthiases. Biohelminthiases are diseases that are transmitted to humans with the participation of animals in whose body the pathogen develops (echinococcosis, alveococcosis, teniasis, teniarinhoz, diphyllobothriasis, opisthorchiasis, trichinosis). Geohelminthiases are diseases that are transmitted to humans through elements of the external environment, where the larval stages of the parasite develop (ascariasis, trichuriasis, necatoriasis). Contact helminthiases are characterized by the transmission of the parasite directly from the patient or through the surrounding objects (enterobiosis, hymenolepiasis). LECTURE No. 17. General characteristics of protozoa (Protozoa) 1. Overview of the structure of protozoa This type is represented by unicellular organisms, the body of which consists of the cytoplasm and one or more nuclei. The cell of the simplest is an independent individual, showing all the basic properties of living matter. It performs the functions of the whole organism, while the cells of multicellular organisms are only part of the organism, each cell depends on many others. It is generally accepted that unicellular beings are more primitive than multicellular ones. However, since the entire body of unicellular organisms, by definition, consists of one cell, this cell must be able to do everything: eat, and move, and attack, and escape from enemies, and survive adverse environmental conditions, and multiply, and get rid of metabolic products, and to be protected from drying out and from excessive penetration of water into the cell. A multicellular organism can also do all this, but each of its cells, taken separately, is good at doing only one thing. In this sense, the cell of the simplest is by no means more primitive than the cell of a multicellular organism. Most representatives of the class have microscopic dimensions - 3-150 microns. Only the largest representatives of the species (shell rhizomes) reach 2-3 cm in diameter. About 100 species of protozoa are known. Their habitat is water, soil, host organism (for parasitic forms). The body structure of a protozoan is typical of a eukaryotic cell. There are general organelles (mitochondria, ribosomes, cell center, EPS, etc.) and special purposes. The latter include organs of movement: pseudopodia, or pseudopodia (temporary outgrowths of the cytoplasm), flagella, cilia, digestive and contractile vacuoles. Organelles of general importance are inherent in all eukaryotic cells. Digestive organelles - digestive vacuoles with digestive enzymes (similar in origin to lysosomes). Nutrition occurs by pino- or phagocytosis. Undigested residues are thrown out. Some protozoa have chloroplasts and feed on photosynthesis. Freshwater protozoa have osmoregulatory organs - contractile vacuoles, which periodically release excess fluid and dissimilation products into the external environment. Most protozoa have one nucleus, but there are representatives with several nuclei. The nuclei of some protozoa are characterized by polyploidy. The cytoplasm is heterogeneous. It is subdivided into a lighter and more homogeneous outer layer, or ectoplasm, and a granular inner layer, or endoplasm. The outer integument is represented by either a cytoplasmic membrane (in amoeba) or a pellicle (in euglena). Foraminifera and sunflowers, inhabitants of the sea, have a mineral, or organic, shell. 2. Features of the vital activity of protozoa The vast majority of protozoa are heterotrophs. Their food can be bacteria, detritus, juices and blood of the host organism (for parasites). Undigested residues are removed through the powder (a special, permanent hole (for ciliates)) or through any place in the cell (for amoeba). Through contractile vacuoles, osmotic regulation is carried out, metabolic products are removed. Respiration, i.e., gas exchange, occurs through the entire surface of the cell. Irritability is represented by taxis (motor reactions). There are phototaxis, chemotaxis, etc. Reproduction of protozoa Asexual - by mitosis of the nucleus and cell division in two (in amoeba, euglena, ciliates), as well as by schizogony - multiple division (in sporozoans). Sexual - copulation. The cell of the protozoan becomes a functional gamete; As a result of the fusion of gametes, a zygote is formed. Ciliates are characterized by a sexual process - conjugation. It lies in the fact that cells exchange genetic information, but there is no increase in the number of individuals. Many protozoa are able to exist in two forms - a trophozoite (a vegetative form capable of active nutrition and movement) and a cyst, which forms under adverse conditions. The cell is immobilized, dehydrated, covered with a dense membrane, the metabolism slows down sharply. In this form, the protozoa are easily carried over long distances by animals, by the wind, and are dispersed. When exposed to favorable living conditions, excystation occurs, the cell begins to function in a trophozoite state. Thus, encystation is not a method of reproduction, but helps the cell to survive adverse environmental conditions. Many representatives of the Protozoa phylum are characterized by the presence of a life cycle consisting in a regular alternation of life forms. As a rule, there is a change of generations with asexual and sexual reproduction. Cyst formation is not part of a regular life cycle. The generation time for protozoa is 6-24 hours. This means that, once in the host's body, the cells begin to multiply exponentially and theoretically can lead to its death. However, this does not happen, since the protective mechanisms of the host organism come into force. Diseases caused by protozoa are called protozoan. The branch of medical parasitology that studies these diseases and their pathogens is called protozoology. Of medical importance are representatives of the protozoa, belonging to the classes of sarcodes, flagellates, ciliates and sporozoans. LECTURE No. 18. Variety of protozoa 1. General characteristics of the Sarcode class (rhizomes) Representatives of this class are the most primitive of the simplest. The main characteristic feature of sarcodes is the ability to form pseudopodia (pseudopodia), which serve to capture food and movement. In this regard, Sarcodidae do not have a permanent body shape, their outer cover is a thin plasma membrane. free-living amoeba More than 10 sarcodes are known. They live in the seas, freshwater reservoirs and in the soil (about 000%). A number of species have moved to a parasitic and commensal way of life. Representatives of the amoeba order (Amoebina) are of medical importance. A typical representative of the class - freshwater amoeba (Amoeba proteus) lives in fresh water, puddles, small ponds. The amoeba moves with the help of pseudopodia, which are formed during the transition of a part of the cytoplasm from the state of the gel to the sol. Nutrition is carried out when the amoeba swallows algae or particles of organic substances, the digestion of which occurs in the digestive vacuoles. The amoeba reproduces only asexually. First, the nucleus undergoes division (mitosis), and then the cytoplasm divides. The body is riddled with pores through which pseudopodia protrude. parasitic amoeba They live in the human body mainly in the digestive system. Some sarcodidae living freely in soil or polluted water can cause serious poisoning, sometimes resulting in death, if ingested by humans. Several types of amoeba have adapted to living in the human intestine. Dysentery amoeba (Entamoeba histolytica) is the causative agent of amoebic dysentery (amebiasis). This disease is widespread everywhere in countries with a hot climate. Invading the intestinal wall, amoebas cause the formation of bleeding ulcers. Of the symptoms, frequent loose stools with an admixture of blood are characteristic. The disease can end in death. It should be remembered that asymptomatic carriage of amoeba cysts is possible. This form of the disease is also subject to mandatory treatment, since carriers are dangerous to others. The intestinal amoeba (Entamoeba coli) is a non-pathogenic form, a normal symbiont of the human large intestine. Morphologically similar to dysenteric amoeba, but does not have such a detrimental effect. It is a typical commensal. These are trophozoites 20-40 microns in size, moving slowly. This amoeba feeds on bacteria, fungi, and in the presence of intestinal bleeding in humans - and red blood cells. Unlike the dysenteric amoeba, it does not secrete proteolytic enzymes and does not penetrate the intestinal wall. It is also capable of forming cysts, but it contains more nuclei (8 nuclei), in contrast to the dysenteric amoeba cyst (4 nuclei). The mouth amoeba (Entamoeba gingivalis) is the first amoeba found in humans. It lives in carious teeth, dental plaque, on the gums and in the crypts of the palatine tonsils in more than 25% of healthy people. It is more common in diseases of the oral cavity. It feeds on bacteria and leukocytes. With gingival bleeding, it can also capture red blood cells. Cyst does not form. The pathogenic effect is unclear. Prevention. 1. Personal. Compliance with the rules of personal hygiene. 2. Public. Sanitary improvement of public toilets, catering establishments. 2. Pathogenic amoeba The dysenteric amoeba (Entamoeba histolytica) is a member of the Sarcodidae class. Lives in the human intestine, is the causative agent of intestinal amoebiasis. The disease is ubiquitous, but is more common in countries with hot and humid climates. The amoeba life cycle includes several stages that differ in morphology and physiology. In the human intestine, this amoeba lives in the following forms: small vegetative, large vegetative, tissue and cysts. The small vegetative form (forma minuta) lives in the intestinal contents. Dimensions - 8-20 microns. It feeds on bacteria and fungi (elements of the intestinal microflora). This is the main form of existence of E. histolytica, which does not bring significant harm to health. A large vegetative form (pathogenic, forma magna) also lives in the contents of the intestine and in the purulent discharge of ulcers in the intestinal wall. Sizes - up to 45 microns. This form has acquired the ability to secrete proteolytic enzymes that dissolve the intestinal wall and cause the formation of bleeding ulcers. Due to this, the amoeba is able to penetrate quite deep into the tissues. The large form has a clear division of the cytoplasm into a transparent and dense ectoplasm (outer layer) and granular endoplasm (inner layer). A nucleus and swallowed red blood cells are found in it, which the amoeba feeds on. The large form is capable of forming pseudopods, with the help of which it vigorously moves deep into the tissues as they are destroyed. A large form can also penetrate into the blood vessels and spread through the bloodstream to organs and systems (liver, lungs, brain), where it also causes ulceration and abscess formation. In the depth of the affected tissues is a tissue form. It is somewhat smaller than a large vegetative one and does not have erythrocytes in the cytoplasm. Amoebas are able to form rounded cysts. Their characteristic feature is the presence of 4 nuclei (in contrast to the intestinal amoeba, whose cysts contain 8 nuclei). The sizes of cysts are 8-16 microns. Cysts are found in the faeces of sick people, as well as parasitic carriers whose disease is asymptomatic. Life cycle of the parasite. A person is affected by amoebiasis by swallowing cysts with contaminated water or food. In the lumen of the large intestine (where the parasite lives) 4 successive divisions occur, as a result of which 8 cells are formed, giving rise to small vegetative forms. If the conditions of existence do not favor the formation of large forms, amoeba encyst and are excreted with feces. Under favorable conditions, small vegetative forms turn into large ones, which cause the formation of ulcers. Plunging into the depths of the tissues, they pass into tissue forms, which, in especially severe cases, penetrate the bloodstream and spread throughout the body. Diagnosis of the disease. Detection of trophozoites with ingested erythrocytes in the feces of a sick person is possible only within 20-30 minutes after the excretion of feces. Cysts are found in the chronic course of the disease and parasitism. It should be borne in mind that in the acute period, both cysts and trophozoites can be found in the feces. 3. General characteristics of the flagellate class Class Flagellates (Flagellata) has about 6000-8000 representatives. This is the most ancient group of protozoa. They differ from sarcodes in their permanent body shape. They live in sea and fresh waters. Parasitic flagellates live in various human organs. A characteristic feature of all representatives is the presence of one or more flagella, which serve for movement. They are located mainly at the anterior end of the cell and are filamentous outgrowths of ectoplasm. Inside each flagellum are microfibrils built from contractile proteins. The flagellum is attached to the basal body located in the ectoplasm. The base of the flagellum is always associated with the kinetosome, which performs an energy function. The body of the flagellar protozoan, in addition to the cytoplasmic membrane, is covered on the outside with a pellicle - a special peripheral film (derivative of ectoplasm). It also ensures the constancy of the shape of the cell. Sometimes a wavy cytoplasmic membrane passes between the flagellum and the pellicle - an undulating membrane (a specific organelle of movement). The movements of the flagellum cause the membrane to wave-like vibrations, which are transmitted to the entire cell. A number of flagellates have a supporting organelle - an axostyle, which, in the form of a dense strand, passes through the entire cell. Flagella - heterotrophs (feed on ready-made substances). Some are also capable of autotrophic nutrition and are mixotrophs (for example, Euglena). Many free-living representatives are characterized by swallowing lumps of food (holozoic nutrition), which occurs with the help of flagellum contractions. At the base of the flagellum is a cellular mouth (cystostomy), followed by a pharynx. Digestive vacuoles form at its inner end. Reproduction is usually asexual, occurring by transverse division. There is also a sexual process in the form of copulation. A typical representative of free-living flagellates is green euglena (Euglena viridis). Inhabits polluted ponds and puddles. A characteristic feature is the presence of a special light-perceiving organ (stigma). The euglena is about 0,5 mm long, the body shape is oval, the posterior end is pointed. Flagellum one, located at the anterior end. Movement with the help of a flagellum resembles screwing. The nucleus is closer to the posterior end. Euglena has characteristics of both a plant and an animal. In the light, nutrition is autotrophic due to chlorophyll, in the dark - heterotrophic. Such a mixed type of nutrition is called mixo-trophic. Euglena stores carbohydrates in the form of paramyl, similar in structure to starch. Euglena's breathing is the same as that of an amoeba. The pigment of the red light-sensitive eye (stigma) - astaxanthin - is not found in the plant kingdom. Reproduction is asexual. Of particular interest are the colonial flagellates - pandorina, eudorina and volvox. On their example, one can trace the historical development of the sexual process. LECTURE No. 19. Pathogenic flagellates Of medical importance are those species of flagellates that parasitize in the body of humans and animals. Trypanosomes (Tripanosoma) are the causative agents of African and American sleepy fevers. These flagellates live in the tissues of the human body. Their transmission to the host is carried out transmissively, i.e. through carriers. Leishmania (Leishmania) - causative agents of leishmaniasis, transmissible diseases with natural foci. Carriers - mosquitoes. Natural reservoirs - rodents, wild and domestic predators. There are three main forms of diseases caused by leishmania - cutaneous, visceral and mucocutaneous leishmaniasis. Giardia intestinalis (Lamblia intestinalis) is the only protozoan that lives in the small intestine. Causes lamb-liosis. Giardia can penetrate into the bile ducts and liver. 1. Trichomonas (Trichomonas vaginalis) and T. hominis These are the causative agents of trichomoniasis. They live in the genital and urinary tracts. Morphological characteristics of Trichomonas Trichomonas (flagellate class) are the causative agents of diseases called trichomoniasis. In the human body live intestinal and vaginal (urogenital) Trichomonas. Urogenital Trichomonas (Trichomonas vaginalis) is the causative agent of urogenital trichomoniasis. In women, this form lives in the vagina and cervix, in men - in the urethra, bladder and prostate gland. It is found in 30-40% of women and 15% of men. The disease is ubiquitous. The length of the parasite is 15-30 microns. The body shape is pear-shaped. It has 4 flagella, which are located at the anterior end of the body. There is an undulating membrane that extends to the middle of the body. In the middle of the body there is an axostyle protruding from the cell at its posterior end in the form of a spike. The core has a characteristic shape: oval, pointed at both ends, reminiscent of a plum stone. The cell contains digestive vacuoles, in which leukocytes, erythrocytes and bacteria of the genitourinary flora, which feed on the urogenital Trichomonas, can be found. Cyst does not form. Infection occurs most often through sexual contact with unprotected sexual contact, as well as when using shared bedding and personal hygiene items: towels, washcloths, etc. Both non-sterile gynecological instruments and gloves during a gynecological examination can serve as a transmission factor. This parasite usually does not cause visible harm to the host, but causes chronic inflammation in the genitourinary tract. This occurs due to the close contact of the pathogen with the mucous membranes. In this case, epithelial cells are damaged, it is exfoliated, micro-inflammatory foci and erosion appear on the surface of the mucous membranes. In men, the disease can spontaneously end in recovery 1-2 months after infection. Women get sick longer (up to several years). Diagnostics. Based on the detection of vegetative forms in a smear of discharge from the genitourinary tract. Prevention - compliance with the rules of personal hygiene, the use of personal protective equipment during sexual intercourse. Intestinal Trichomonas (Trichomonas hominis) is a small flagellate (length - 5-15 microns) that lives in the large intestine. It has 3-4 flagella, one nucleus, an undulating membrane and an axostyle. It feeds on intestinal bacteria. The formation of cysts was not established. Infection occurs through food and water contaminated with Trichomonas. When ingested, the parasite multiplies rapidly and can cause diarrhea. It is also found in the intestines of healthy people, that is, carriage is possible. Diagnostics. Based on the detection of vegetative forms in feces. Prevention. 1. Personal. Compliance with the rules of personal hygiene, heat treatment of food and water, thorough washing of vegetables and fruits (especially those contaminated with earth). 2. Public. Sanitary arrangement of public places, monitoring of sources of public water supply, sanitary and educational work with the population. 2. Giardia (Lamblia intestinalis) Giardia belong to the class Flagella. It is the only protozoan that lives in the human small intestine. Causes a disease called intestinal giardiasis. They most often affect young children. It lives in the small intestine, mainly in the duodenum, can penetrate into the bile ducts (intrahepatic and extrahepatic), and from there - into the gallbladder and liver tissue. Giardiasis is ubiquitous. Morphology The size of the parasite is 10-18 microns. The shape of the body resembles a pear cut in half. The body is clearly divided into right and left halves. In this regard, all organelles and nuclei are paired. Symmetrically located 2 semi-lunar nuclei (in the middle of the body) and 4 pairs of flagella. In the expanded part there is a suction disk, with the help of which the parasite is attached to the villi of the small intestine. Along the body are 2 thin axo styles. Life features of lamblia Giardia are capable of forming cysts, which are excreted with feces and thus spread into the environment. Cysts form in the lower parts of the small intestine. Mature cysts are oval in shape, contain 4 nuclei and several supporting axostyles. In the external environment, they are quite resistant to adverse conditions and remain viable for several weeks. Infection of a person occurs by swallowing cysts that have fallen into food or drinking water. In the small intestine, excystation occurs, vegetative forms (trophozoites) are formed. With the help of suction cups, they are attached to the villi of the small intestine. Giardia use nutrients that they capture from the surface of intestinal epithelial cells using pinocytosis. If there are a large number of Giardia in the intestine, they are able to cover rather large surfaces of the intestinal epithelium. In this regard, the processes of parietal digestion and absorption of food are significantly disrupted. In addition, the presence of Giardia in the intestine causes inflammation. Penetrating into the bile ducts, they cause inflammation of the gallbladder and disrupt the outflow of bile. Giardia can be found in apparently healthy people. Then there is an asymptomatic carriage. However, these people are dangerous, as they can infect others. Diagnostics. Based on the detection of cysts in feces. Trophozoites can be found in the contents of the duodenum, obtained by fractional duodenal sounding. Prevention. 1. Personal. Compliance with personal hygiene rules (such as washing hands before eating and after going to the toilet, thoroughly washing fruits and vegetables, heat treatment of food and drinking water, etc.). 2. Public. Sanitary improvement of public toilets, catering establishments, sanitary and educational work with the population. 3. Leishmaniae (Leishmaniae) Leishmania (Leishmania) are the protozoa of the flagella class. They are the causative agents of leishmaniasis - transmissible diseases with natural foci. Diseases in humans are caused by several species of this parasite: L. tropica - the causative agent of cutaneous leishmaniasis, L. donovani - the causative agent of visceral leishmaniasis, L. brasiliensis - the causative agent of Brazilian leishmaniasis, L. mexicana - the causative agent of the Central American form of the disease. All of them have morphological similarities and the same cycles of development. They exist in two forms: flagellated (leptomonas, otherwise promastigote) and non-flagellated (leishmanial, otherwise amastigote). The leishmanial form is very small (3-5 microns), rounded. Has no flagellum. It lives in the cells of the reticuloendothelial system of humans and some animals (rodents, dogs). The flagellate form is elongated (up to 25 microns), has a flagellum at the anterior end. It is found in the digestive tract of carriers (small mosquitoes of the genus Phlebotomus). These forms can also form in artificial cultures. Natural reservoir - rodents, wild and domestic predators. Leishmania are widespread in countries with tropical and subtropical climates, on all continents where mosquitoes are present. In cutaneous leishmaniasis, the lesions are in the skin. This is the most common form. The course of the disease is relatively benign. Called by L. tropica, L. mexicana and some L. brasiliensis biovars. After a mosquito bite, rounded, long-term non-healing ulcers form on exposed parts of the body. After healing, scars remain. Immunity is lifelong. Some forms of L. brasiliensis can migrate through the lymphatics, causing ulceration far from the site of the bite. The mucocutaneous form is caused by the subspecies L. brasiliensis brasiliensis. Leishmania penetrate from the skin through the blood vessels into the mucous membrane of the nasopharynx, larynx, soft palate, genital organs, causing destructive changes in the mucous membranes. Diagnostics Discharge is taken from a skin or mucous ulcer and smears are prepared for subsequent microscopy. The visceral form of the disease is caused by L. donovani. The incubation period is long, the disease begins several months or years after infection. Children under 12 years of age are more often affected. The disease proceeds as a systemic infection. Parasites multiply in tissue macrophages and blood monocytes. Very high toxicity. Impaired function of the liver, hematopoiesis. If left untreated, the disease is fatal. Diagnostics A punctate of red bone marrow is obtained (with puncture of the sternum) or lymph nodes, followed by the preparation of a smear or imprint for microscopy. In stained preparations, the leishmanial form of the parasite is found, both extra- and intracellularly. In doubtful cases, the material is sown on nutrient media, where the leishmanial form turns into a flagellate, actively moves and is detected by conventional microscopy. Biological samples are used (eg infection of laboratory animals). Prevention Vector control (mosquitoes), destruction of natural reservoirs, preventive vaccinations. 4. Trypanosomes (Tripanosoma) The causative agents of trypanosomiasis are trypanosomes (flagellate class). African trypanosomiasis (sleeping fevers) is caused by Trypanosoma brucei gambiensi and T. b. rhodesiense. American trypanosomiasis (Chagas disease) is caused by Trypanosoma cruzi. The parasite has a curved body, flattened in one plane, pointed on both sides. Dimensions - 15-40 microns. Stages living in the human body have 1 flagellum, an undulating membrane and a kinetoplast located at the base of the flagellum. In the body of humans and other vertebrates, the parasite lives in blood plasma, lymph, lymph nodes, cerebrospinal fluid, the substance of the brain and spinal cord, and serous fluids. The disease is ubiquitous throughout Africa. Trypanosomiasis caused by these parasites is a typical transmissible disease with natural foci. The causative agent of trypanosomiasis develops with a change of hosts. The first part of the life cycle takes place in the body of the carrier. Trypanosoma brucei gambiensi is carried by Glossi-na palpalis (near human habitation) tsetse flies, T. b. rho-desiense, Glossina morsitans (in open savannas). The second part of the life cycle takes place in the body of the final host, which can be large and small cattle, humans, pigs, dogs, rhinos, antelopes. When a tsetse fly bites a sick person, trypanosomes enter its stomach. Here they multiply and go through several stages. A full development cycle takes 20 days. Flies whose saliva contains trypanosomes in an invasive (meta-cyclic) form can infect humans when bitten. Sleeping sickness without treatment can take a long time (up to several years). Patients have progressive muscle weakness, exhaustion, drowsiness, depression, mental retardation. Self-healing is possible, but most often the disease ends fatally without treatment. Trypanosomiasis caused by T. b. Rhodesiense, is more malignant and ends in death 6-7 months after infection. Diagnostics Examine blood smears, cerebrospinal fluid, conduct a biopsy of the lymph nodes in which pathogens are visible. Prevention Vector control, prophylactic treatment of healthy people in the foci of trypanosomiasis, making the body immune to the pathogen. Trypanosoma cruzi is the causative agent of American trypanosomiasis (Chagas disease). The pathogen is characterized by the ability to intracellular habitation. They multiply only in the cells of the myocardium, neuroglia and muscles (in the form of non-flagellated forms), but not in the blood. Carriers - triatom bugs. Trypanosomes multiply in their body. After the bite, the bugs defecate, the pathogen in the invasive stage enters the wound with feces. The pathogen lives in the tissues of the heart, brain, muscles. This disease is characterized by myocarditis, hemorrhages in the meninges, their inflammation. Diagnostics Detection of the pathogen in the blood (in the acute period). In chronic course - infection of laboratory animals. Prevention The same as in African trypanosomiasis. 5. General characteristics of the class Sporozoa About 1400 species of sporozoans are known. All representatives of the class are parasites (or commensals) of humans and animals. Many sporozoans are intracellular parasites. It is these species that have undergone the most profound degeneration in terms of structure: their organization has been simplified to a minimum. They do not have any organs of excretion and digestion. Nutrition occurs due to the absorption of food by the entire surface of the body. Waste products are also excreted through the entire surface of the membrane. There are no respiratory organelles. Common features of all representatives of the class are the absence of any movement organelles in mature forms, as well as a complex life cycle. For sporozoans, two variants of the life cycle are characteristic - with and without the presence of the sexual process. The first version of the cycle includes the stages of asexual reproduction and the sexual process (in the form of copulation and sporogony). Asexual reproduction is carried out by simple division using mitosis or by multiple division (schizogony). In schizogony, multiple nuclear divisions occur without cytokinesis. Then the entire cytoplasm is divided into parts, which are isolated around new nuclei. From one cell, a lot of daughters are formed. Before the sexual process, the formation of male and female germ cells - gametes. They are called gamonts. The opposite-sex gametes then fuse to form a zygote. She puts on a dense shell and turns into a cyst in which sporogony occurs - multiple division with the formation of cells (sporozoites). It is at the sporozoite stage that the parasite enters the host organism. Sporozoans, which are characterized by just such a development cycle, live in the tissues of the internal environment of the human body (for example, malarial plasmodia). The second variant of the life cycle is much simpler and consists of the stage of a cyst and a trophozoite (an actively feeding and reproducing form of the parasite). Such a development cycle is found in sporozoans that live in cavity organs that communicate with the external environment. Basically, sporozoans that parasitize in humans and other vertebrates live in body tissues. They can affect both humans and many animals (including wild ones). Thus, these are zoonotic and anthropozoonotic diseases, the prevention of which is a difficult task. These diseases can be transmitted non-transmissively (like toxoplasma), i.e., not have a specific carrier, or transmissively (like malarial plasmodia), i.e. through carriers. Diagnosis of diseases caused by protozoa of the Sporovidae class is quite difficult, since parasites can live in various organs and tissues (including deep ones), which reduces the likelihood of their detection. In addition, the severity of the symptoms of the disease is low, since they are not strictly specific. Toxoplasma (Toxoplasma gondii) - causative agents of toxoplasmosis. Man is an intermediate host for this parasite, and the main hosts are cats and other members of the feline family. Malarial Plasmodium is the causative agent of malaria. Man is the intermediate host, the final host is mosquitoes of the genus Anopheles. 6. Toxoplasmosis: causative agent, characteristics, development cycle, prevention The causative agent of toxoplasmosis is Toxoplasma gondii. It affects a huge number of species of animals, as well as humans. The parasite, localized in the cells, has the shape of a crescent, one end of which is pointed and the other is rounded. In the center of the cell is the nucleus. At the pointed end there is a structure similar to a sucker - a conoid. It serves for fixation and introduction into host cells. The life cycle is typical for sporozoans. There is an alternation of asexual and sexual reproduction - schizogony, gametogenesis and sporogony. The definitive hosts of the parasite are cats and other members of the feline family. They get the pathogen by eating the meat of sick animals (rodents, birds) or infected meat of large herbivores. In the intestinal cells of a cat, parasites first reproduce by schizogony, and many daughter cells are formed. Next, gametogenesis proceeds, gametes are formed. After their copulation, oocysts are formed, which are released into the external environment. Sporogony proceeds under the cyst membrane, many sporozoites are formed. Sporocysts with sporozoites enter the body of an intermediate host - humans, birds, many mammals, and even some reptiles. Getting into the cells of most organs, Toxoplasma begin to multiply actively (multiple division). As a result, under the shell of one cell is a huge number of pathogens (a pseudocyst is formed). When one cell is destroyed, many pathogens come out of it, which penetrate into other cells. Other groups of toxoplasma in the host cells are covered with a thick shell, forming a cyst. In this state, Toxoplasma can persist for a long time. They are not released into the environment. The development cycle closes when cats eat infected meat from intermediate hosts. In the body of a sick person, Toxoplasma is found in the cells of the brain, liver, spleen, in the lymph nodes and muscles. A person as an intermediate host can get toxoplasma when eating the meat of infected animals, through damaged skin and mucous membranes when caring for sick animals, when processing infected meat or skins, transplacentally (toxoplasma is able to pass through a healthy placenta), during medical manipulations - donor transfusion blood and its preparations, transplantation of donor organs against the background of taking immunosuppressants (suppressing the body's natural defenses). In most cases, there is an asymptomatic parasitism or a chronic course without characteristic symptoms (if the parasites are of low pathogenicity). In rare cases, the disease is acute: with a rise in temperature, an increase in peripheral lymph nodes, the appearance of a rash and manifestations of general intoxication. This is determined by the individual sensitivity of the organism and the routes of penetration of the parasite. Prevention Thermal treatment of food products of animal origin, sanitary control at slaughterhouses and meat processing plants, exclusion of contact between pregnant women and children with pets. 7. Malarial Plasmodium: morphology, development cycle Malarial plasmodia belong to the class Plasmodium and are the causative agents of malaria. The following types of plasmodia parasitize in the human body: P. vivax - the causative agent of three-day malaria, P. malariae - the causative agent of four-day malaria, P. falciparum - the causative agent of tropical malaria, P. ovale - the causative agent of ovalemalaria, close to three-day (found only in Central Africa). The first three species are common in tropical and subtropical countries. All types of Plasmodium have similar features of the structure and life cycle, the difference is only in certain details of morphology and some features of the cycle. The life cycle is typical for sporozoans and consists of asexual reproduction (schizogony), sexual process and sporogony. Malaria is a typical anthroponotic vector-borne disease. The carriers are mosquitoes of the genus Anopheles (they are also the final hosts). The intermediate host is only a human. Human infection occurs when a mosquito bites, the saliva of which contains plasmodia at the sporozoite stage. They penetrate into the blood, with the current of which they end up in the liver tissue. Here tissue (preerythrocytic) schizogony occurs. It corresponds to the incubation period of the disease. In liver cells, sporozoites develop into tissue schizonts, which increase in size and begin to divide schizogony into thousands of daughter individuals. At the same time, liver cells are destroyed, and parasites at the merozoite stage enter the bloodstream. They are introduced into erythrocytes, in which erythrocyte schizogony occurs. The parasite absorbs the hemoglobin of blood cells, grows and multiplies by schizogony. Moreover, each plasmodium produces from 8 to 24 merozoites. Hemoglobin consists of an inorganic iron-containing part (heme) and a protein (globin). The food of the parasite is globin. When the affected erythrocyte bursts, the parasite enters the bloodstream, and heme enters the blood plasma. Free heme is the strongest poison. It is his entry into the blood that causes terrible attacks of malarial fever. The patient's body temperature rises so high that in the old days malaria infection was used as a treatment for syphilis (Spanish scabies): treponema cannot withstand such temperatures. The development of plasmodia in erythrocytes goes through four stages: rings (trophozoite), amoeboid schizont, fragmentation (formation of morula) and (for some parasites) formation of gametocytes. When an erythrocyte is destroyed, merozoites enter the blood plasma, and from there into new erythrocytes. The cycle of erythrocyte schizogony is repeated many times. The growth of a trophozoite in an erythrocyte takes a time constant for each species of Plasmodium. An attack of fever is timed to coincide with the release of parasites into the blood plasma and recurs every 3 or 4 days, although with a long-term illness, the alternation of periods may be fuzzy. Some of the merozoites in erythrocytes form immature hamonts, which are an invasive stage for the mosquito. When a mosquito bites a sick person, the gamonts enter the mosquito's stomach, where mature gametes are formed from them. After fertilization, a mobile zygote (ookinete) is formed, which penetrates under the epithelium of the mosquito's stomach. Here it increases in size, becomes covered with a dense membrane, and an oocyst is formed. Inside it, multiple division occurs, in which a huge number of sporozoites are formed. Then the shell of the oocyst bursts, plasmodia with blood flow penetrate into all the tissues of the mosquito. Most of them accumulate in his salivary glands. Therefore, when bitten by a mosquito, sporozoites can enter the human body. Thus, in humans, plasmodium reproduces only asexually - schizogony. Man is an intermediate host for the parasite. In the body of the mosquito, the sexual process proceeds - the formation of a zygote, many sporozoites are formed (sporogony is in progress). The mosquito is the definitive host and also the carrier. Malaria: pathogenic significance, diagnosis, prevention. Malaria is a severe disease characterized by periodic debilitating attacks of fever with chills and profuse sweating. With the release of a large number of merozoites from erythrocytes, many toxic waste products of the parasite itself and the decay products of hemoglobin, which feeds on plasmodium, are released into the blood plasma. When exposed to them on the body, severe intoxication occurs, which manifests itself in a sharp paroxysmal increase in body temperature, the appearance of chills, headaches and muscle pain, and severe weakness. The temperature can reach significant levels (40-41 ° C). These attacks occur acutely and last an average of 1,5-2 hours. This is followed by thirst, dry mouth, a feeling of heat. After a few hours, the temperature drops to normal numbers, all symptoms stop, the patients fall asleep. In general, the entire attack lasts from 6 to 12 hours. There are differences in the intervals between attacks in different types of malaria. With three-day and oval malaria, attacks are repeated every 48 hours. Their number can reach 10-15, after which they stop, as antibodies against the pathogen begin to be produced in the body. Parasites in the blood can still be detected, so a person becomes a parasite carrier and poses a danger to others. In malaria caused by P. malariae, the intervals between attacks are 72 hours. Asymptomatic carriage is common. In tropical malaria, at the onset of the disease, the intervals between attacks may be different, but then they are repeated every 24 hours. With this type of malaria, there is a high risk of death due to complications from the central nervous system or kidneys. Tropical malaria is especially dangerous for Caucasians. A person can become infected with malaria not only through the bite of an infected mosquito. Infection is also possible through hemo-transfusion (transfusion) of infected donor blood. Most often, this method of infection occurs with four-day malaria, since there are few schizonts in erythrocytes, they may not be detected when examining the blood of donors. Diagnostics It is possible only during the period of erythrocyte schizogony, when the pathogen can be detected in the blood. Plasmodium, recently penetrated into the erythrocyte, has the form of a ring. The cytoplasm in it in the form of a rim surrounds a large vacuole. The nucleus is displaced to the edge. Gradually, the parasite grows, pseudopods appear in it (in the amoeboid schizont). It occupies almost the entire erythrocyte. Further, fragmentation of the schizont occurs: a deformed erythrocyte contains many merozoites, each of which contains a nucleus. In addition to asexual forms, gametocytes can also be found in erythrocytes. They are larger, do not have pseudopods and vacuoles. Prevention Identification and treatment of all patients with malaria (elimination of the source of mosquito invasion) and extermination of mosquitoes (elimination of vectors) with the help of special insecticides and reclamation works (draining swamps). When traveling to areas unfavorable for malaria, you should take prophylactic antimalarial drugs, protect yourself from mosquito bites (use mosquito nets, apply repellents to the skin). LECTURE No. 20. Class Ciliates (ciliary) There are about 6000 known species belonging to the class Ciliates. Most representatives are inhabitants of marine and fresh water bodies, some live in moist soil or sand. Many species are parasites of humans and animals. 1. Overview of the structure of ciliates Ciliates are the most complex protozoa. They have numerous organelles of movement - cilia, which completely cover the entire body of the animal. They are much shorter than the flagella and are polymerized flagella. The number of cilia can be very large. In different species, cilia may be present only in the early stages of development, while in others they may persist for life. Electron microscopy revealed that each cilium consists of a certain number of fibers (microtubules). Each cilium is based on a basal body, which is located in a transparent ectoplasm. Another feature: each individual has at least two nuclei - large (macronucleus) and small (micronucleus). Sometimes there may be several micro- and macronuclei. The large nucleus is responsible for metabolism, and the small nucleus regulates the exchange of genetic information during the sexual process (conjugation). The macronuclei of ciliates are polyploid, while the micronuclei are haploid or diploid. During the sexual process, the macronucleus is destroyed, and the micronucleus meiotically divides with the formation of four nuclei, of which three die, and the fourth divides mitotically with the formation of male and female haploid nuclei. Between the two ciliates, a temporary cytoplasmic bridge appears in the area of cytostomes. The male nucleus of each individual passes into the partner's cell, the female remains in place. Each cell merges its own female nucleus with the partner's male nucleus. Then the micronucleus is restored, the ciliates diverge. The number of cells does not increase, but the exchange of genetic information occurs. All ciliates have a constant body shape, which is ensured by the presence of a pellicle (a dense shell that covers the entire body from the outside). There is a complexly constructed power apparatus. On the so-called ventral side of the ciliate there is a permanent formation - a cellular mouth (cytostome), which passes into the pharynx (cytopharynx). The pharynx opens directly into the endoplasm. Water with bacteria contained in it (food of ciliates) is driven into the mouth with the help of cilia, from where it enters the cytoplasm and is surrounded by a digestive vacuole. The vacuole moves through the cytoplasm, while digestive enzymes are released gradually (this ensures more complete digestion). The undigested residue is thrown out through a special hole - powder. There are two contractile vacuoles, contracting alternately every 20-25 s. Reproduction of ciliates for the most part occurs by transverse division. From time to time, the sexual process is carried out in the form of conjugation. A typical representative of the class is the ciliate shoe, which lives in small ponds, puddles. A characteristic feature of this representative is the presence of trichocysts - small spindle-shaped bodies that are thrown out when irritated. They serve both for defense and for attack. In the human body, the only representative of the class parasitizes - balantidia, which lives in the digestive system and is the causative agent of balantidiasis. 2. Balantidium (Balantidium coli) Balantidia is the causative agent of balantidiasis. This disease is ubiquitous. Lives in the human large intestine. This ciliate is one of the largest protozoa: its size is 30-200, 20-70 microns. The body shape is oval. It has many structural features characteristic of free-living ciliates. The entire body of balantidia is covered with numerous short cilia, the length of which around the cell mouth (cytostomy) is somewhat longer than in other parts of the body. In addition to the cytostome, there are cytopharyngs and powder. There is a pellicle, under which there is a layer of transparent ectoplasm. Deeper is the endoplasm with organelles and two nuclei - a macronucleus and a micronucleus. The large nucleus is usually bean-shaped or dumbbell-shaped, with a small nucleus located nearby. At the anterior and posterior ends of the body, there is one pulsating vacuole each, which are involved in the regulation of osmotic balance in the cell. In addition, vacuoles secrete dissimilation products (metabolism). Balantidia forms oval or spherical cysts, up to 50-60 microns in diameter. The cyst is covered with a two-layer membrane and has no cilia. The micronucleus is usually not visible in it, but the contractile vacuole is clearly visible. Balantidia, like other ciliates, reproduces by transverse division. Sometimes there is a sexual process in the form of conjugation. Human infection occurs with cysts through contaminated water and food. The cysts can also be carried by flies. Both pigs and rats, in which this protozoan parasitizes in the intestines, can serve as sources of the spread of the disease. In humans, the disease manifests itself in the form of asymptomatic carriage or acute illness, which is accompanied by intestinal colic. In addition, balantidia can live in the human intestine, feeding on bacteria and not causing much harm. However, it can penetrate the wall of the colon, causing bleeding and festering ulcers. The disease is characterized by the appearance of prolonged bloody diarrhea with pus. Sometimes perforation of the intestinal wall occurs (a hole appears in the wall), fecal peritonitis develops. In severe cases of the disease (especially with peritonitis and perforation), patients may even die. As with amoebic dysentery, balantidia can penetrate into the bloodstream from the intestinal wall and be carried throughout the body with blood flow. It is able to settle in the lungs, liver, brain, where it can cause the formation of abscesses. Diagnostics Microscopy of a smear of the patient's feces. In the smear, cysts and trophozoites of balantidia are found. Mucus, blood, pus and a lot of parasites are revealed. Prevention. 1. Personal. Compliance with the rules of personal hygiene. 2. Public. Sanitary arrangement of public places, monitoring of sources of public water supply, sanitary and educational work with the population, rodent control, hygienic keeping of pigs. LECTURE No. 21. Type Flatworms (Plathelminthes) 1. Characteristic features of the organization The type has about 7300 species, combined into such three classes as: 1) Ciliary worms; 2) Flukes; 3) Tapeworms. They are found in marine and fresh waters. Some species have switched to a parasitic way of life. The main aromorphoses of flatworms: 1) bilateral symmetry of the body; 2) development of the mesoderm; 3) the emergence of organ systems. Flatworms are bilaterally symmetrical animals. This means that all the organs of their body are located symmetrically in relation to the right and left sides. The tissues and organs of their body develop from three germ layers - ecto-, endo- and mesoderm. Adaptation to crawling on the substrate led to the appearance of their ventral and dorsal, right and left sides, as well as the anterior and posterior ends of the body. The body of a flatworm is flattened dorsoventrally. They do not have a body cavity, the entire space between the internal organs is filled with loose connective tissue - the parenchyma. Flatworms have developed organ systems: muscular, digestive, excretory, nervous and sexual. They have a skin-muscular sac. It consists of an integumentary tissue - a tegument, which is a non-cellular multinuclear structure of the syncytium type, and three layers of smooth muscles running in the longitudinal, transverse and oblique directions. The body of flukes is covered with a cuticle that protects them from the action of the digestive juices of the host. All movements carried out by flatworms are slow and imperfect. The nervous system consists of paired nerve nodes (ganglia) located at the head end of the trunk, from which parallel longitudinal nerve trunks extend posteriorly. The digestive system (if any) begins with the pharynx and ends with a blindly closed intestine. There are anterior and middle intestines. The hindgut and anus are absent. In this case, undigested food residues are thrown out through the mouth. In flatworms, for the first time, an excretory system appears, which consists of organs called protonephridia, they begin in the depths of the parenchyma with terminal (terminal) stellate cells. Protonephridia capture metabolic products and move them along intracellular channels that run inside the long processes of protonephridial cells. Further, the products to be excreted enter the collecting ducts, and from there either directly to the external environment or to the bladder. The reproductive system of worms is complex. Flatworms combine the characteristics of both sexes - male and female. Most ciliary worms are free-living predators. Representatives of two classes are of medical importance - Flukes (Trematodes) and Tapeworms (Cestoidea). Fluke representatives The liver fluke (fasciola) is the causative agent of fasciolosis (the giant liver fluke causes more severe fascioliasis), the feline, or Siberian, fluke is the causative agent of opisthorchiasis, schistosomes are the causative agents of schistosomatosis. In addition, fasciolopsis, the causative agent of fasciolopsidiasis (inhabits the small intestine), clonorchis, the causative agent of clonorchiasis (inhabits the bile ducts of the liver), pulmonary fluke (paragonimus), which lives in the lung tissue, parasitizes in the human body, it causes paragonimiasis, etc. representatives of tapeworms Wide tapeworm is the causative agent of diphyllobothriasis, bovine tapeworm is the causative agent of teniarhynchosis, pork tapeworm is the causative agent of teniasis and cysticercosis, echinococcus is the causative agent of echinococcosis and alveococcus is the causative agent of alveococcosis. 2. Class Flukes. general characteristics Flukes (Trematodes) are parasitic organisms. About 3000 species of flukes are known. These parasites are characterized by complex cycles of development in which there is an alternation of generations, as well as methods of reproduction and hosts. The sexually mature individual has a leaf-shaped form. The mouth is located at the terminal end of the body and is equipped with a powerful muscular sucker. In addition to it, there is another sucker on the ventral side. Additional organs of attachment in some species are small spines that cover the entire body. The digestive system of small species of flukes is a bag or two blindly ending canals. In large species, it is strongly branched. In addition to the function of proper digestion, it also performs a transport role - it redistributes food throughout the body. Flatworms, including flukes, do not have an internal body cavity, which means there is no circulatory system. The leaf-shaped form of the body allows the intestine to supply the entire body with nutrients. The same shape makes gas exchange possible across the entire surface of the body, since there are simply no organs and tissues lying deep under the cuticle. Flukes are hermaphrodites. Male reproductive system: a pair of testes, two vas deferens, ejaculatory canal, copulatory organ (cirrus). In the liver fluke, the testes are branching, in the feline and lanceolate, they are compact. Female reproductive system: ovary, oviducts, vitelline glands, seminal receptacle, uterus, genital cloaca. The yolk glands provide the egg with nutrients, the shell glands provide the membranes. Insemination is internal, cross. The eggs mature in the uterus. A sexually mature individual (marita) always lives in the body of a vertebrate animal. She releases eggs. For further development, the egg must fall into the water, where the larva, the miracidium, emerges from it. The larva has light-sensitive eyes and cilia, and is able to independently search for an intermediate host using various types of taxis. Miracidium must enter the body of a gastropod mollusk, which is strictly specific for this type of parasite. In his body, the larva turns into a maternal sporocyst, which undergoes the most profound degeneration. It has only female reproductive organs, and therefore reproduces only parthenogenetically. During its reproduction, multicellular redia are formed, which also reproduce by parthenogenesis. The last generation of redia can generate cercariae. They leave the body of the mollusk and for further development must enter the body of the final or second intermediate host. In the first case, cercariae either actively invade the body of the final host, or encyst on the grass and are swallowed with it. In the second case, cercariae look for those animals that are used by the main host for food, and form resting stages in their body - encysted metacercariae. The bulk of cercariae die without entering the body of the main host, since they are incapable of active search, or they enter the body of those species in which development is impossible. The ability of the parasite to reproduce in the larval stages greatly increases its population. After penetration into the organism of the final host, the invasive stages of flukes migrate in it and find the organ necessary for further development. There they reach sexual maturity and live. Migration through the body is accompanied by severe intoxication and allergic manifestations. Diseases caused by flukes are collectively called trematodes. 3. Class Flukes. Its representatives Liver fluke. Morphology, development cycle, ways of infection, prevention The liver fluke, or fasciola (Fasciola hepatica), is the causative agent of fascioliasis. The disease is widespread everywhere, most often in countries with a hot and humid climate. The parasite lives in the bile ducts, liver, gallbladder, sometimes the pancreas and other organs. The size of the marita's body is 3-5 cm. The shape of the body is leaf-shaped, the anterior end is beak-like drawn. It is necessary to pay special attention to the structure of the genital organs. The uterus is multilobed and is located in a rosette just behind the ventral sucker. Behind the uterus lies the ovary. On the sides of the body are numerous zheltochnik and branches of the intestine. The entire middle part of the body is occupied by highly branched testes. The eggs are large (135-80 microns), yellowish-brown, oval, with a cap on one of the poles. The life cycle of the liver fluke is typical for this group of parasites. Fasciola develops with a change of hosts. Herbivorous mammals (large and small cattle, horses, pigs, rabbits, etc.), as well as humans, serve as the final host. The intermediate host is the small pond snail (Limnea truncatula). Infection of the main host occurs when he eats grass from water meadows (for animals), unwashed greens and vegetables (for humans). Usually a person becomes infected when eating sorrel and watercress. On green plants are ado-lescaria - cercaria encysted on the leaves. After entering the intestines of the final host, the larva is released from the membranes, perforates the intestinal wall and penetrates into the circulatory system, from there into the liver tissue. With the help of suckers and spines, fasciola destroys liver cells, which causes bleeding and the formation of cirrhosis in the outcome of the disease. The liver increases in size. From the liver tissue, the parasite can penetrate into the bile ducts and cause blockage, jaundice appears. The parasite reaches sexual maturity 3-4 months after infection and begins to lay eggs while in the bile ducts. Diagnostics Detection of fasciola eggs in the faeces of a patient. Eggs can also be found in the feces of a healthy person when he eats the liver of animals with fascioliasis (transit eggs). Therefore, if you suspect a disease before the examination, it is necessary to exclude the liver from the diet. Prevention Thoroughly wash vegetables and herbs, especially in areas endemic for fascioliasis, where vegetable gardens are watered with standing water. Do not use unfiltered water for drinking. Identify and treat sick animals, sanitize pastures, change pastures and pastures of geese and ducks to destroy the intermediate host. Sanitary education is of great importance. Cat fluke. Morphology, development cycle, ways of infection, prevention The feline, or Siberian, fluke (Opisthorchis felineus) is the causative agent of opisthorchiasis. This parasite lives in the liver, gallbladder and pancreas of humans, cats, dogs and other animal species that eat raw fish. In our country, the foci of the disease are located along the banks of the rivers of Siberia; individual foci - in the Baltic, along the banks of the Kama, Volga, Dnieper. Natural foci of the disease are known in Kazakhstan. The cat fluke has a pale yellow color, its length is 4-13 mm. In the middle part of the body is a branched uterus, behind it is a rounded ovary. A characteristic feature is the presence in the back of the body of two rosette-shaped testes, which are well stained. The eggs of the cat's fluke are 25-30 X 10-15 microns in size, yellowish in color, oval, narrowed towards the pole, have a lid at the front end. The final hosts of the parasite are wild and domestic mammals and humans. The first intermediate host is the mollusc Bithinia leachi. The second intermediate host is carp fish, in the muscles of which metacercariae are localized. First, an egg with miracidium enters the water. Then it is swallowed by a mollusk, in the hindgut of which the miracidium leaves the egg, penetrates into the liver and turns into a sporocyst. In it, by parthenogenesis, numerous generations of redia develop, of which cercariae. Cercariae leave the body of the mollusk, enter the water and, actively swimming in it, penetrate into the body of the fish or are swallowed by it and penetrate into the subcutaneous fatty tissue and muscles. Shells form around the parasite. This stage of development is called metacercariae. When the definitive host eats raw or dried fish, metacercariae enter its gastrointestinal tract. Under the influence of enzymes, the membranes dissolve. The parasite enters the liver and gallbladder and reaches sexual maturity. Thus, for the first intermediate host, the invasive stage is an egg with miracidium, for the second - cercariae, for the final - metacercariae. Opisthorchiasis is a serious disease. With the simultaneous parasitization of many individuals, it can end in death. In some patients, cases of liver cancer have been reported, which may be provoked by constant irritation of the organ by the presence of flukes. Diagnostics Laboratory detection of feline fluke eggs in feces and duodenal contents obtained from a patient. Prevention Compliance with the rules of personal hygiene. Sanitary and educational work. Eating only well-cooked or fried fish (heat treatment of products). Schistosomes. Morphology, development cycle, ways of infection, prevention Schistosomes are the causative agents of schistosomiasis. All parasites live in blood vessels, mainly in veins. They are found in a number of countries with a tropical and subtropical climate (mainly in Asia, Africa, and South America). Unlike other flukes, schistosomes are dioecious organisms. The body of males is shorter and wider. The females are cord-shaped. Young individuals live separately, but when they reach puberty, they join in pairs. After that, the female lives in the gynecophore canal on the ventral side of the male. Since schistosomes live in blood vessels, their eggs have devices for excretion into the abdominal organs, and from there into the external environment. All eggs have spines through which various enzymes are released that dissolve the tissues of the host's body. With the help of these enzymes, eggs pass through the vessel wall and enter the tissues. They can penetrate the intestines or bladder (depending on the type of parasite). From these abdominal organs, parasites enter the external environment. Hematogenous drift (through blood vessels) of eggs into many internal organs is possible, which is very dangerous due to the development of local multiple inflammatory processes in these organs. For some species of schistosomes, only humans are the definitive host, for others (along with humans) - various species of mammals. Intermediate hosts are freshwater mollusks. In their body, the development of larval stages occurs, which reproduce parthenogenetically with the formation of two generations of sporocysts. The last generation forms cercariae, which are the invasive stage for the definitive host. Cercariae have a characteristic appearance: a forked tail, and at the anterior end there are specific penetration glands, with the help of which the final host enters the body when it is in the water. At the same time, larvae of cercaria float freely in water and are able to actively pierce the skin of the human body when bathing, working in rice fields and in water, drinking water from irrigation canals, etc. Clothing does not protect against the ingress of the parasite into the body. When penetrating through the skin, cercariae cause a specific lesion in the form of cercariasis. Their signs are the appearance of a rash, itching, allergic conditions. If cercariae enter the lungs in large numbers, severe pneumonia can occur. Larvae of schistosomes pathogenic for humans are carried throughout the body with blood flow. They settle mainly in the veins of the abdominal cavity or small pelvis, where they reach sexual maturity. Diagnostics Detection in the urine or feces of a patient of eggs of schistosomes. Allergological skin tests are possible, immunological diagnostic methods are used. Prevention Use only disinfected water for drinking. Avoid prolonged contact with water in areas endemic for schistosomiasis. Fight against an intermediate host - aquatic molluscs. Protection of water bodies from pollution by untreated sewage. Different types of schistosomiasis Three main types of blood flukes parasitize in the human body. This is Schistosoma heamatobium, Sch. mansoni and Sch. japonicum. They differ in a number of biological features, habitat in the human body and geographical distribution. All schistosomiasis are natural focal diseases. Distributed in the tropics of Asia, Africa and America. Schistosoma heamatobium - the causative agent of urogenital schistosomiasis, lives in the large veins of the abdominal cavity and organs of the genitourinary system. The disease is distributed from Africa to Southwest India. The final host is man and monkeys. Intermediate hosts are various aquatic mollusks. The male parasite has a length of up to 1,5 cm, and the female - up to 2 cm. The surface of the body is finely bumpy. The eggs are very large, up to 160 mm, have a spike, with which they destroy the wall of the vessel. With the blood flow, they penetrate the bladder and organs of the reproductive system and are excreted in the urine. Urogenital schistosomiasis is characterized by the presence of blood in the urine (hematuria), pain above the pubis. Often there is the formation of stones in the urinary tract. In places where this disease is spread, bladder cancer is much more common. Diagnostics Detection of parasite eggs by microscopy of urine. Characteristic changes in the bladder and vagina during examination are inflammation, polyposis growths, ulcerations. Schistosoma mansoni is the causative agent of intestinal schistosomiasis. The range is much wider than that of the previous species. It is found in Africa, Indonesia, the countries of the Western Hemisphere - Brazil, Guyana, the Antilles, etc. It parasitizes in the veins of the mesentery and large intestine. It also affects the portal system of the liver. Unlike the previous species, it has a slightly smaller size (up to 1,6 cm) and a coarsely bumpy body surface. The eggs are the same size as those of Schistosoma heamatobium, but, unlike them, the spike is located on the lateral surface. The final hosts of the parasite are humans, monkeys, dogs, and rodents. Intermediate hosts are aquatic mollusks. With the defeat of this parasite, pathological changes occur mainly in the large intestine (colitis, bloody diarrhea) and the liver (blood stasis occurs, cancer is possible). Diagnostics Detection of eggs in the faeces of the patient. Schistosoma japonicum is the causative agent of Japanese schistosomiasis. The range covers East and Southeast Asia (Japan, China, the Philippines, etc.). It parasitizes in the blood vessels of the intestine. It does not differ in size from Sch. heamatobium, but has a very smooth body. The eggs are round, the spine is very small, it is located on the lateral surface of the body. The final hosts are humans, many domestic and wild mammals. Intermediate hosts are aquatic mollusks. The manifestations of the disease correspond to those of intestinal schistosomiasis. But parasite eggs are much more likely to penetrate other organs (including the brain), so the disease is severe and often ends in death. Diagnostics Detection of eggs in the faeces of the patient. 4. General characteristics of the class Tapeworms Class Tapeworms (Cestoidea) has about 3500 species. All of them are obligate parasites that live in the intestines of humans and other vertebrates at sexual maturity. The body (strobila) of the tapeworm has a ribbon-like shape, flattened in the dorso-ventral direction. Consists of separate segments - proglottids. At the anterior end of the body is the head (scolex), which may be round or flattened, followed by an unsegmented neck. Attachment organs are located on the head - suckers, hooks, suction slots (bothria). New proglottids bud from the neck and move back. Thus, the farther from the neck, the more mature the segments. In young joints, organs and systems are not differentiated. In the middle part of the strobili are mature segments with fully developed male and female reproductive systems (tapeworms are hermaphrodites). The most recent segments contain almost exclusively the uterus with eggs, and the remaining organs are represented by rudiments. During the growth of the worm, the posterior segments gradually break off and are released into the environment, and young proglottids take their place. The body structure of a tapeworm is in many ways typical of flatworms. But there are also differences. Due to the fact that these worms lead an exclusively parasitic lifestyle and live in the intestines, their digestive system is completely absent. Absorption of nutrients from the host intestine occurs osmotically throughout the body surface. Life cycle. All tapeworms have two stages in their development - sexually mature (live in the body of the final host) and larval (parasite in the intermediate host). The first stages of egg development occur in the uterus. Here, inside the shells of the egg, a six-hooked embryo is formed - an onco-sphere. With the faeces of the host, the egg enters the external environment. For further development, the egg must enter the digestive system of the intermediate host. Here, with the help of hooks, the egg pierces the intestinal wall and enters the bloodstream, from where it spreads to organs and tissues, where it develops into a larva - a Finn. Usually it has a cavity inside and a formed head. Infection of the final hosts occurs by eating the meat of infected animals, in the tissues of which there are Finns. In the intestines of the final host, under the influence of its digestive enzymes, the shell of the Finn dissolves, the head turns outward and attaches to the intestinal wall. From the neck, the formation of new segments and the growth of the parasite begin. The main host does not suffer much from this parasite, which lives in the intestines. But the vital activity of intermediate hosts can be severely impaired, especially if the tapeworm Finns live in its brain, liver or lungs. Diseases caused by tapeworms are called cestodosis. Many species of these parasites affect only humans, but there are also those that are found in the natural environment. They are characterized by the presence of natural foci. 5. Chains Bull tapeworm. Morphology, development cycle, prevention Bovine, or unarmed, tapeworm (Taeniarhynchus saginatus) is the causative agent of teniarhynchosis. The disease occurs everywhere in areas where the population eats raw or undercooked (boiled) meat of cattle. In the sexually mature stage, the bull tapeworm reaches a length of 4-7 m. There are only 4 suckers on the head, there are no hooks (hence the name). In the middle part of the body there are hermaphrodite segments of a square shape. The uterus does not branch, the ovary has only two lobes. Each segment contains up to 1000 vesicular testicles. Mature segments at the posterior end of the body are strongly elongated, the uterus in them forms a huge number of lateral branches and is stuffed with a large number of eggs (up to 175000.). The eggs contain oncospheres (diameter 10 µm) covered with a thin shell. Each oncosphere has 3 pairs of hooks and a thick, radially striated shell. The final owner of the bovine tapeworm is only humans, the intermediate hosts are cattle. Animals become infected by eating grass, hay and other food with proglottids, which, along with feces, get there from a person. In the stomach of cattle, oncospheres come out of the eggs, which are deposited in the muscles of animals, forming Finns. They are called cysticerci. A cysticercus is a fluid-filled vesicle with a head with suction cups screwed into it. In the muscles of livestock, Finns can persist for many years. A characteristic feature of the parasite is the ability of its segments to actively crawl out of the anus one by one. A person becomes infected by eating raw or half-cooked meat from an infected animal. In the stomach, under the influence of the acidic environment of the gastric juice, the shell of the Finn dissolves, the larva comes out, which attaches to the intestinal wall. The effect on the host organism is: 1) the effect of taking food; 2) intoxication with the waste products of the parasite; 3) imbalance of intestinal microflora (dysbacteriosis); 4) impaired absorption and synthesis of vitamins; 5) mechanical irritation of the intestine; 6) possible development of intestinal obstruction; 7) inflammation of the intestinal wall. Sick people lose weight, they have no appetite, they are disturbed by pain in the abdomen and disruption of the intestines (alternating constipation and diarrhea). Diagnostics Detection in the feces of a patient of mature segments with a specific structure. Segments can also be found on the body and underwear of a person. Prevention. 1. Personal. Thorough heat treatment of beef and veal. 2. Public. Strict supervision of the processing and sale of meat in meat processing plants, slaughterhouses, markets. Carrying out sanitary and educational work with the population. Pork tapeworm. Morphology, development cycle, prevention Pork, or armed, tapeworm (Taenia solium) - the causative agent of teniasis. The disease occurs everywhere in areas where the population eats raw or undercooked pork meat. In the human body, the parasite lives in the small intestine and can be found in the eyes, central nervous system, liver, muscles, and lungs. Sexually mature forms reach a length of 2-3 m. There are suckers on the head, as well as a corolla of 22-32 hooks. Hermaphroditic proglottids have a male reproductive apparatus, which consists of several hundred testes and a tortuous ejaculatory canal, turning into a cirrus bag. It passes into the cloaca and opens outward. There are distinctive features in the structure of the female reproductive system. The ovary has a third additional lobule and more branches (7-12), which is an important diagnostic feature. The eggs are no different from the eggs of the tapeworm. Life cycle. The final owner is only a human. Intermediate hosts - a pig, occasionally a man. A characteristic feature: segments are excreted with human feces not one at a time, but in groups of 5-6 pieces. When the eggs dry, their shell bursts, the eggs disperse freely. Flies and birds also contribute to this process. Pigs become infected by eating sewage, which may contain proglottids. In the stomach of pigs, the egg shell dissolves, six-hooked oncospheres emerge from it. Through the blood vessels, they enter the muscles, where they settle and after 2 months turn into Finns. They are called cysticerci and are a vial filled with liquid, inside of which a head with suction cups is screwed. In pork, cysticerci are the size of a grain of rice and are visible to the naked eye. Human infection occurs by eating raw or undercooked pork. Under the action of digestive juices, the cysticercus membrane dissolves; the scolex is everted, which is attached to the wall of the small intestine. Then new proglottids begin to form from the neck. After 2-3 months, the parasite reaches sexual maturity and begins to produce eggs. With this disease, reverse intestinal peristalsis and vomiting often occur. At the same time, mature segments enter the stomach and are digested there under the influence of gastric juice. The released oncospheres enter the intestinal vessels and are carried through the bloodstream to organs and tissues. They can enter the liver, brain, lungs, eyes, where they form cysticerci. Cysticercosis of the brain is often the cause of death of patients, and cysticercosis of the eye leads to loss of vision. Treatment of cysticercosis is only surgical. Diagnostics Detection in the feces of a patient of mature segments with a specific structure. The segments can also be found on the human body and underwear, as they can crawl out of the anus and move actively. Prevention. 1. Personal. Thoroughly cooked pork. 2. Public. Protection of pastures from contamination by human feces. Strict supervision of the processing and sale of meat in meat processing plants, slaughterhouses, markets. Dwarf tapeworm. Morphology, development cycle, prevention Dwarf tapeworm (Hymenolepis nana) is the causative agent of hymeno-lepidosis. The disease occurs everywhere, especially in countries with a hot and dry climate. Predominantly children of preschool age are ill. At the age of 7 to 14 years, the disease is rarely recorded, in the older one it almost never occurs. In the human body, it lives in the small intestine. Dwarf tapeworm has a small length (1,5-2 cm). The head is pear-shaped, has 4 suckers and a proboscis with a halo of hooks. The strobilus contains 200 or more segments. They are very tender, so they are destroyed in the intestines. As a result, only eggs are released into the environment. The size of the eggs is up to 40 microns. They are colorless and have a rounded shape. The life cycle of the parasite has undergone significant changes during the long period of adaptation to humans. This parasite has acquired the ability to develop without changing hosts in the human body for a long time, without leaving it at the egg stage. Thus, a person for a pygmy tapeworm is both an intermediate and a definitive host. If a person swallows the eggs of a pygmy tapeworm with non-compliance with the rules of personal hygiene, they enter the small intestine, where their shell dissolves under the influence of digestive enzymes. Oncospheres emerge from the eggs, which penetrate into the villi of the small intestine, where cystic cercoids develop from them. In front, they have a swollen part with a screwed head, and a caudal appendage is located at the posterior end of the body. After a few days, the affected villi are destroyed, and cystic cercoids fall into the intestinal lumen. Juveniles attach to the intestinal mucosa and reach sexual maturity. There are cases when in the intestines of one person there were up to 1500 tapeworms at the same time. The eggs of this parasite may not be released into the external environment and turn into sexually mature individuals already in the intestine. First, cysticercoids are formed from them, and then adult tapeworms, i.e., repeated self-infection (autoreinvasion) occurs. pathogenic action. Part of the villi of the small intestine is destroyed, which leads to disruption of the processes of parietal digestion. In addition, the body is poisoned by the waste products of the helminth. Intestinal activity is disturbed, abdominal pains, diarrhea, headaches, irritability, weakness, fatigue appear. The disease cannot continue indefinitely, as the human body is able to develop immunity against the parasite. It hinders the development of subsequent generations of the parasite, especially during autoreinvasion. After a change of several generations, self-healing occurs. Diagnostics Detection of eggs of the pygmy tapeworm in the faeces of the patient. Prevention. 1. Personal. Compliance with the rules of personal hygiene, instilling hygiene skills in children. 2. Public. Thorough cleaning of children's institutions (especially toilets), sterilization of toys. A constant struggle is needed with mechanical egg carriers, i.e. with insects. Echinococcus. Morphology, routes of infection, development cycle, prevention Echinococcus (Echinococcus granulosus) is the causative agent of echinococcosis. The disease occurs throughout the globe, but most often in those countries where animal husbandry is developed. The sexually mature form of the parasite is 2-6 mm long and consists of 3-4 segments. The penultimate hermaphrodite (i.e., it has female and male genital organs). The last segment is mature and contains a uterus with up to 5000 eggs containing oncospheres. Echinococcus eggs are similar in shape and size to the eggs of porcine and bovine tapeworms. On the head (scolex) there are 4 suckers and a proboscis with two rims of hooks. Life cycle. The final owners are predatory animals of the Canine family (dogs, jackals, wolves, foxes). Intermediate hosts are herbivores (cows, sheep), pigs, camels, rabbits and many other mammals, as well as humans. The definitive host becomes infected by eating the tissues of the infected intermediate host. The faeces of the definitive hosts contain parasite eggs. In addition, mature segments of echinococcus can actively crawl out of the anus and spread through the fur of animals, leaving eggs on it. This increases the likelihood of pasture pollution. Humans and other intermediate hosts become infected by ingesting eggs (most often they first fall on the hands from the hair of dogs, and then are brought into the mouth). In the human digestive tract, an oncosphere emerges from the egg, which penetrates the bloodstream and is carried through the bloodstream to organs and tissues. There she turns into a Finn. In echinococcus, it is a bubble, often reaching enormous sizes (up to 20-30 cm in diameter). The bladder wall has an outer layered capsule and an inner parenchymal membrane. On it, daughter individuals can form, which bud off from the wall. Inside the bubble contains a liquid with the waste products of the parasite. Echinococcus has a very large pathogenic effect on the human body. In the larval stage, it can be located in a variety of organs: the liver, brain, lungs, tubular bones. Finna can squeeze the organs, causing them to atrophy. Tissues are destroyed, the body works much worse. Metabolic products of the parasite constantly enter the internal environment of the human body, causing severe intoxication. Dangerous rupture of the echinococcal bladder. Since it contains liquid with dissimilation products of the parasite, if it enters the bloodstream, toxic shock may occur, which is fraught with the death of the patient. At the same time, the daughter scolexes seed the tissues, causing the development of new Finns. Treatment of echinococcosis is only surgical. Diagnostics According to the Cassoni reaction: 0,2 ml of sterile liquid from the echinococcal bladder is injected subcutaneously. If within 3-5 minutes the formed bubble increases five times, the reaction is considered positive. Prevention Compliance with the rules of personal hygiene, especially when dealing with animals. Destruction of stray dogs, examination and treatment of domestic and service animals. Destruction of the corpses of sick animals. Wide ribbon. Morphology, routes of infection, development cycle, prevention Wide tapeworm (Diphyllobotrium latum) - the causative agent of diphyllobothriasis. The disease occurs mainly in countries with a temperate climate. In Russia - along the banks of the Volga, Dniester and other large rivers. In humans, the parasite resides in the small intestine. In the sexually mature state, the parasite has a length of up to 7-10 m or more. The head of the parasite (scolex) is devoid of suckers. It is attached to the intestinal wall with the help of two bothria, or suction slits, which look like grooves. Proglottids are wider than long. The uterus has a characteristic rosette-like shape and small size. It contacts the external environment through an opening at the anterior edge of each proglottid. Therefore, ripening eggs can freely come out of it. Eggs of a wide tapeworm are wide, oval, up to 70 microns in size, yellowish-brown in color. On one pole they have a cap, on the other - a small tubercle. The life cycle of the parasite is the most ancient among tapeworms. It retains the larval stage, actively swimming in the water - coracidium. There are two intermediate hosts that live in the water - small freshwater crustaceans (Cyclops and Diaptomus) and fish that feed on them. The final hosts are humans and carnivorous mammals (cats, lynxes, foxes, arctic foxes, dogs, bears, etc.). Eggs enter the water with human feces. After 3-5 weeks, a mobile coracidium covered with cilia comes out of the egg, which has 3 pairs of hooks. Coracidia are swallowed by crustaceans (the first intermediate host), in the intestines of which they lose their cilia and turn into a larva - a procercoid. The procercoid has an elongated body shape and 6 hooks. If the crustacean is swallowed by a fish (the second intermediate host), the procercoid passes into the next (larval) stage in its muscles - the plerocercoid. A person becomes infected by eating raw or half-cooked fish or freshly salted caviar. When salting, marinating, frying meat, plerocercoids die. Diphyllobothriasis is a dangerous disease. The parasite infringes on the mucosa with its suction slits and can cause its necrosis. Due to the large size of the helminth, intestinal obstruction often occurs. The effect of taking food appears: the parasite consumes nutrients from the intestines, but the person does not receive them (wasting occurs). Intoxication is a consequence of the release of toxic products of life of the parasite into the blood. Dysbacteriosis often occurs, as the parasite is in antagonism with the normal intestinal microflora. There is a violation of the absorption of vitamin B12 from the intestine, as a result of which a severe form of B12-deficiency anemia of folic acid may occur. Diagnostics. Detection of eggs and fragments of mature segments of the broad tapeworm in faeces. Prevention. 1. Personal. Refusal to eat raw fish (which is often found as an established cultural tradition among the peoples of the Far North), careful heat treatment of fish. 2. Public. Protection of water bodies from fecal pollution. LECTURE No. 22. Type Roundworms (Nemathelminthes) 1. Features of the structure More than 500 species of roundworms have been described. They live in different environments: sea and fresh waters, soil, decaying organic substrates, etc. Many worms have adapted to a parasitic way of life. The main aromorphoses of the type: 1) primary body cavity; 2) the presence of the posterior intestine and anus; 3) dichotomy. In all roundworms, the body is unsegmented, has a more or less rounded shape in cross section. The body is three-layered, develops from endo-, meso- and ectoderm. There is a skin-but-muscular bag. It consists of an outer inextensible dense cuticle, hypodermis (represented by a single multinuclear cytoplasmic mass without boundaries between cells - syncytium) and one layer of longitudinal smooth muscle fibers. The cuticle plays the role of the external skeleton (support for the muscles), protects against the effects of adverse environmental factors. In the hypodermis, metabolic processes are actively taking place. It also delays all products that are toxic to the helminth. The muscle layer consists of individual cells, which are grouped into 4 strands of longitudinal muscles - dorsal, abdominal and two lateral. Roundworms have a primary body cavity, a pseudocoel, which is filled with fluid. It contains all the internal organs. They form five differentiated systems - digestive, excretory, nervous, sexual and muscular. The circulatory and respiratory systems are absent. In addition, the fluid gives the body elasticity, plays the role of a hydroskeleton and ensures the exchange of substances between internal organs. The digestive system is presented in the form of a through tube, which begins with a mouth opening, surrounded by cuticular lips, at the anterior end of the body, and ends with an anus at the posterior end of the body. The digestive tube consists of three sections - anterior, middle and posterior. Pinworms have a bulb - an expansion of the esophagus. The nervous system consists of the head ganglia, the peripharyngeal ring and the nerve trunks extending from it - the dorsal, abdominal and two lateral. The most developed dorsal and ventral nerve trunks. Between the trunks there are connecting bridges. The sense organs are very poorly developed, represented by tactile tubercles and chemical sense organs. The excretory system is built according to the type of protonephridia, but the number of excretory cells is much less. The function of excretion is also possessed by special phagocytic cells that accumulate metabolic products and foreign bodies that have entered the body cavity. Roundworms have dichotomy. The genital organs have a tubular structure. In the female they are usually paired, in the male they are unpaired. The male reproductive apparatus consists of the testis, the vas deferens, which passes into the ejaculatory canal. It opens into the hindgut. The female reproductive apparatus begins with paired ovaries, followed by two oviducts in the form of tubes and paired uterus, which are connected to a common vagina. Reproduction of roundworms is only sexual. The number of cells that make up the body of roundworms is always limited. Therefore, they have little opportunity in terms of growth and regeneration. Representatives of only one class are of medical importance - the actual Roundworms. There are biohelminths that develop with the participation of intermediate hosts, and geohelminths that have retained contact with the external environment (their eggs or larvae develop in the soil). 2. Roundworms - human parasites Ascaris Ascaris human (Ascaris lumbricoides) is the causative agent of ascariasis. The disease is widespread almost everywhere. The human roundworm species is close in morphology to the swine roundworm, which is found in Southeast Asia, where it can easily infect humans, and the human roundworm can infect pigs. The human roundworm is a large geohelminth, the females of which reach a length of 40 cm in a mature state, and males - 20 cm. The body of the roundworm is cylindrical, narrowed towards the ends. In the male, the posterior end of the body is spirally twisted to the ventral side. Mature eggs of the parasite are oval in shape, surrounded by a thick multi-layered shell, tuberous. They have a yellowish-brown color, sizes up to 60 microns. Ascaris human is a geohelminth that parasitizes almost exclusively in humans. Fertilized eggs are excreted from the human body with feces and must enter the soil for further development. Eggs mature in high humidity, oxygen and optimum temperature of 24-25°C in 2-3 weeks. They are resistant to adverse environmental factors (they can remain viable for 6 years or more). A person becomes infected with ascaris most often through unwashed vegetables and fruits, on which the eggs are located. In the human intestine, a larva emerges from the egg, which makes complex migrations through the human body. It perforates the intestinal wall, first penetrates into the veins of the systemic circulation, then through the liver, right atrium and ventricle enters the lungs. From the capillaries of the lungs, it goes into the alveoli, then into the bronchi and trachea. This causes the formation of a cough reflex, which contributes to the entry of the parasite into the throat and secondary ingestion with saliva. Once in the human intestine again, the larva turns into a sexually mature form, which is able to reproduce and lives for about a year. The number of roundworms simultaneously parasitizing in the intestines of one person can reach several hundred or even thousands. At the same time, one female gives up to 240 eggs per day. pathogenic action. General intoxication with waste products of ascaris, which are very toxic. Headache, weakness, drowsiness, irritability develop, memory and working capacity decrease. Invasion with a large number of ascaris can lead to the development of mechanical intestinal obstruction, appendicitis, blockage of the bile ducts (with mechanical jaundice developing), abscesses can form in the liver. There are cases of atypical localization of ascaris in the ear, throat, liver, heart. This requires urgent surgical intervention. Migrating larvae cause destruction of lung tissue and the formation of foci of purulent infection. Diagnostics. Detection of human roundworm eggs in the patient's feces. Prevention 1. Personal. Compliance with the rules of personal hygiene, thorough washing of vegetables, berries, fruits, short cutting of nails, under which there may be eggs of the parasite. 2. Public. Sanitary and educational work. Prohibition of fertilizing vegetable gardens and berries with faeces that have not undergone special treatment. Pinworm Pinworm (Enterobius vermicularis) is the causative agent of enterobiosis. The disease is ubiquitous, more common in children's groups (hence the name). The pinworm is a small white worm. Sexually mature females reach a length of 10 mm, males - 2-5 mm. The body is straight, pointed backwards. The rear end of the body of the male is spirally twisted. Pinworm eggs are colorless and transparent, oval, asymmetrical, flattened on one side. Egg sizes - up to 50 microns. The pinworm parasitizes only in the human body, where the mature individual is localized in the lower sections of the small intestine, feeding on its contents. There is no change of owners. A female with mature eggs leaves their anus at night and lays a huge number of eggs in the folds of the anus (up to 15000), after which she dies. Crawling of the parasite on the skin causes itching. Characteristically, eggs reach invasive maturity within a few hours after laying. Persons suffering from enterobiosis comb itchy places in their sleep, while a huge number of eggs fall under the nails. From the hands they are brought into the mouth by the patient himself (auto-reinvasion occurs) or scattered over the surface of linen and objects. When eggs are swallowed, they enter the small intestine, where sexually mature parasites rapidly develop. The life expectancy of an adult pinworm is 56-58 days. If during this time a new self-infection has not occurred, a person's self-healing occurs. pathogenic action. Due to itching of the perineum, children often experience poor sleep, lack of sleep, irritability, deterioration in well-being, and school performance often decreases. When the parasite penetrates into the appendix, inflammation of the latter is possible, i.e., the development of appendicitis (which happens more often than with ascariasis). Since the parasites are located on the surface of the mucous membrane of the small intestine, its inflammation and violation of the integrity of the intestinal wall are possible. The effect of food withdrawal most often does not develop, since the parasite is small and does not require such an amount of nutritional material as, for example, tapeworms. Diagnostics The diagnosis is based on the detection of pinworm eggs in the material from the perianal folds and on the detection of parasites crawling out of the anus. In the feces of patients with enterobiasis, pinworms and their eggs are most often absent. Prevention 1. Personal. Careful observance of the rules of personal hygiene, health education of the population. Thorough washing of hands, especially before eating and after sleep, short cutting of nails. Sick children need to wear panties at night, which are thoroughly washed and ironed in the morning (pinworms cannot stand high temperatures). 2. Public. Regular examination of children (especially in organized groups) and staff, employees of catering establishments for enterobiasis. Whitewash Human whipworm (Trichocephalus trichiurus) is the causative agent of trichuriasis. The disease has a fairly wide, almost universal distribution. The causative agent is localized in the lower parts of the small intestine (mainly in the caecum), the upper parts of the large intestine. A sexually mature individual of the whipworm is up to 3-5 cm long. The anterior end of the body is much narrower than the posterior one and is filiformly elongated. It contains only the esophagus. The rear end of the body of the male is spirally twisted and thickened. It contains the reproductive system and intestines. Whipworm eggs are shaped like barrels, with cork-shaped lids at the ends. The eggs are light, transparent, up to 50 microns long. The life span of the parasite is up to 6 years. Vlasoglav parasitizes only in the human body. There is no change of owners. This is a typical geohelminth that develops without migration (unlike the human roundworm). For further development, helminth eggs with human feces must enter the external environment. They develop in the soil in conditions of high humidity and a fairly high temperature. Eggs reach invasiveness within 3-4 weeks after entering the soil. A larva develops inside the egg. Human infection occurs by ingestion of eggs containing whipworm larvae. This is possible when eating vegetables, berries, fruits or other foods contaminated with eggs, as well as water. In the human intestine, under the action of digestive enzymes, the shell of the egg dissolves, and the larva emerges from it. The parasite reaches sexual maturity in the human intestine a few weeks after infection. pathogenic action. The parasite is located in the intestines, where it feeds on human blood. It does not absorb the contents of the intestine, in connection with this, the removal of this parasite from the human body is quite difficult and requires special perseverance from the doctor (drugs administered orally have no effect on the parasite). The anterior end of the body of the whipworm sinks quite deeply into the intestinal wall, which can significantly disrupt its integrity and cause inflammation. There is an intoxication of the human body with the products of the vital activity of the parasite: headaches, increased fatigue, decreased efficiency, drowsiness, irritability appear. Intestinal function is impaired, abdominal pain occurs, and there may be convulsions. Since the parasite feeds on blood, anemia (anemia) can occur. Dysbacteriosis often develops. With massive invasion, whipworms can cause inflammatory changes in the appendix (appendicitis). Diagnostics Detection of whipworm eggs in the feces of a sick person. Prevention. 1. Personal. Compliance with the rules of personal hygiene, thorough washing of vegetables, berries and fruits. 2. Public. Sanitary and educational work with the population, improvement of public latrines and public catering establishments. Trichinella Trichinella (Trichinella spiralis) is the causative agent of trichinosis. The disease occurs episodically everywhere on all continents and in all climatic zones, but there are certain natural foci. In Russia, almost all cases of trichinosis occurred in the forest zone, which suggests that the disease is a natural focal and is associated with certain animal species, which in this area are the natural reservoir of the parasite. Localization. Trichinella larvae live in the striated muscles, and sexually mature individuals live in the small intestine, where they lie between the villi, penetrating the lymphatic capillaries with the anterior end of the body. Morphologically, Trichinella is a very small parasite: females are up to 2,5-3,5 mm long, and males - 1,4-1,6 mm. Life cycle. Trichinella is a typical biohelminth whose life cycle is associated only with the host organism. Getting into the environment for further development and infection is not at all necessary. In addition to the human body, Trichinella parasitize pigs, rats, cats and dogs, wolves, bears, foxes and many other wild and domestic mammals. Any animal in whose body Trichinella lives is both an intermediate and a definitive host. The spread of the disease usually occurs when animals eat infected meat. Swallowed larvae in the intestine quickly reach sexual maturity in the host's small intestine. After fertilization in the intestines, males quickly die, and females give birth to about 2-1500 live larvae for 2000 months, after which they also die. The larvae pierce the intestinal wall, penetrate the lymphatic system, then spread throughout the body with blood flow, but settle mainly in certain muscle groups: diaphragm, intercostal, masticatory, deltoid, gastrocnemius. The migration period is usually 2-6 weeks. Having penetrated into the muscle fibers (some of which die at the same time), the larvae spirally twist and encapsulate (the shell calcifies). In such dense capsules, larvae can live for several decades. A person becomes infected by eating the meat of animals affected by trichinosis. Thermal effects on meat during conventional cooking do not have a detrimental effect on the parasite. pathogenic action. The clinical manifestations of the disease are different: from asymptomatic course to death, which depends primarily on the number of larvae in the body. The incubation period is 5-45 days. There is a general toxic-allergic effect on the body (exposure to the waste products of the parasite and the development of immune system reactions to it). The mechanical influence of the parasite on the muscle fibers is important, which affects the work of the muscles. Diagnostics Anamnestically - the use of meat of wild animals or untested meat. Examination of a muscle biopsy for the presence of a parasite. Immunological reactions are applied. Prevention Thermal processing of meat. Meat that has not been checked by a veterinarian should not be eaten. Sanitary supervision in pig breeding, pork inspection. hookworm (crooked head) Crooked head of the duodenum (Ancylostoma duodenale) is the causative agent of ankylostomiasis. The disease is widespread throughout the subtropical and tropical climates with high temperatures and humidity. There are cases of occurrence of foci of the disease in temperate zones under conditions of high soil moisture and its contamination with feces. Hookworms are worm-shaped, reddish-colored parasites. The female has a length of 10-18 mm, males - 8-10 mm. The front end is bent to the dorsal side (hence the name). At the head end of the parasite there is an oral capsule with 4 chitinous teeth. Hookhead eggs are oval, transparent, with blunt poles, up to 60 µm in size. The life expectancy of the parasite is 4-5 years. In the human body, it lives in the small intestine (mainly in the duodenum). Refers to geohelminths that migrate in the human body (like roundworm). It parasitizes only in humans. Fertilized eggs with faeces enter the environment, where, under favorable conditions, larvae, called rhabditic, emerge from them in a day. They are non-invasive. The larvae actively feed on faeces and decaying organic matter and molt twice. After that, the larva becomes invasive (these are filariform larvae). They can enter the human body through the mouth with contaminated food and water. But most often the larvae are actively introduced through the skin. Since infection occurs mainly by contact with the soil, people of those professions that are associated with the earth are most often infected (these are diggers, gardeners, miners, etc.). In the human body, larvae migrate. First, they penetrate from the intestines into the blood vessels, from there to the heart and lungs. Rising through the bronchi and trachea, they penetrate the pharynx, causing the development of a cough reflex. Repeated swallowing of the larvae with saliva leads to the fact that they again enter the intestine, where they settle in the duodenum. With its oral capsule, the crookhead captures a small area of the mucous membrane and, damaging its villi, feeds on blood. Parasites secrete anticoagulant substances that prevent blood from clotting, so intestinal bleeding can occur. pathogenic action. There is intoxication of the body with the products of the vital activity of the parasite. Perhaps the development of massive (due to the duration) intestinal bleeding, which leads to severe anemia. It is possible to develop an allergy to the parasite. There are pains in the abdomen, indigestion, headaches, weakness, fatigue. Children can noticeably lag behind in development. In the absence of proper treatment, death is possible. Diagnostics Detection of larvae and eggs in the patient's feces. Prevention. 1. Personal. You should not walk without shoes on the ground in areas where hookworm is common. 2. Public. Early detection and treatment of patients with ankylostomiasis. Pest control must be carried out in the mines. All miners must have flasks of clean water. Guinea worm Rishta (Dragunculus medinensis) - the causative agent of dragunkulosis. The disease is widespread in countries with a tropical and subtropical climate (in Iraq, India, equatorial Africa, etc.). Previously, it was found only in Central Asia. The parasite has a filamentous shape, the length of the female is from 30 to 150 cm with a thickness of 1-1,7 mm, the male is only up to 2 cm long. The life cycle of the parasite is associated with the change of hosts and the aquatic environment. The final host is a human, as well as a monkey, sometimes a dog and other wild and domestic mammals. Intermediate host - cyclops crustaceans. In humans, the parasite is localized in the subcutaneous adipose tissue, mainly of the lower extremities. Cases of finding risht under the serous membrane of the stomach, esophagus, meninges are described. Guinea worm females are viviparous. A huge bubble filled with serous fluid forms above the anterior end of the female's body. In this case, an abscess occurs, a person feels severe itching. It goes away when the skin comes in contact with water. When lowering the legs into the water, the bubble bursts, a huge number of living larvae come out of it. Their further development is possible when cyclops enter the body, which swallow these larvae. In the body of the cyclops, the larvae turn into microfilariae. When drinking contaminated water, the definitive host may ingest a cyclops with microfilariae. In the stomach of this host, the cyclops is digested, and the microfilaria of the guinea worm first enters the intestine, where it pierces its wall and enters the bloodstream. With the blood stream, they are brought into the subcutaneous fatty tissue, where they reach sexual maturity after about 1 year and begin to produce larvae. The development of the parasite in the body of infected people occurs synchronously (with an interval of 1 year). Larvae appear in females at about the same time in all carriers of the parasite. This achieves the simultaneous infection of a large number of cyclops, which increases the likelihood of the parasite penetrating the body of the final host in an arid climate with rare rains. pathogenic action. In places where the parasite is located, severe itching and hardening of the skin appear. If the parasite is located next to the joint, its mobility is disturbed: the patient cannot walk. Painful ulcers and abscesses occur on the skin, which can be complicated by a secondary infection. The parasite also has a general toxic and allergic effect on humans due to the release of its metabolic products into the blood. Diagnostics. With a typical localization of the parasite before the formation of ulcers on the skin, visual detection of sexually mature forms is possible, which look like convoluted, clearly visible ridges under the skin. With atypical localization (for example, in serous and meninges), immunological tests are required. Prevention. 1. Personal. You should not drink unfiltered and unboiled water from open reservoirs in the foci of the disease. 2. Public. Timely detection and treatment of patients, protection of water supply sites, organization of water pipes in public places. There is an old saying: "If he drinks holy water in Bukhara, he will break through and he has guinea worm on his leg." Roundworms - biohelminths Biohelminths are parasites that develop with the participation of intermediate hosts. Among roundworms, only a relatively small group of parasites needs vectors, that is, they are transmitted transmissively. All of them are found in tropical and subtropical climates. They belong to the Fillariodea family and cause similar diseases - filariasis. The role of the main host is performed by humans, great apes and other mammals. Carriers - blood-sucking insects (mosquitoes, midges, horseflies, midges). Sexually mature individuals (fillaria) live in the tissues of the internal environment. They give birth to larvae (microfilariae), which periodically enter the blood and lymph. When bitten by a blood-sucking insect, the larvae enter its stomach, from there into the muscles, where they become invasive and pass into the proboscis of the insect. When bitten by the main host, the vector infects it with a parasite in the invasive stage. Since the development of the parasite also occurs in the body of carriers, it is also an intermediate host (they are always specific for each type of filariae). The release of filaria into the bloodstream is always combined with the time of maximum activity of the carrier. If the carriers are mosquitoes, the larvae enter the bloodstream in the evening and at night, if horseflies, then they come out mainly in the afternoon and in the morning. When filariae are carried by biting midges or midges, the release of the parasite is devoid of periodicity, since the vital activity of biting biting is determined mainly by moisture. The main types of filariae are human parasites. 1. Wuchereria banctofti. Found in equatorial Africa, Asia, South America. The carriers are mosquitoes. The final host is a human, as well as monkeys. In their body, parasites are localized in the lymph nodes and blood vessels, causing stagnation of blood and lymph, elephantiasis, and allergization appear. 2. Brugia malayi. Distributed in Southeast Asia. The carriers are mosquitoes. The final owner is a man, as well as higher monkeys, felines. Localization and pathogenic action are the same as those of Wuchereria banctofti. 3. Oncocerca volvulus. It is found in equatorial Africa, Central, North and South America. Carriers - midges. The final owner is a human. In the body, parasites are localized under the skin of the chest, head, limbs, causing the formation of painful nodules. With localization in the eye area, blindness is possible. 4 Loa loa. Distributed in West Africa. Carriers - horseflies. The final host is a human, as well as monkeys. Localization in the body: under the skin and mucous membranes, where painful nodules and abscesses occur. 5. Mansonella. Found in Central and South America. Carriers - midges. The final host is a person in whose body the parasite is localized in adipose tissue, under the serous membranes, in the mesentery of the intestine. 6. Acantocheilonema. It differs from the previous disease in the range of the parasite: it is South America, equatorial Africa. Diagnosis detection of microfilariae in the blood. Blood should be taken at the time of day when the detection of the parasite is most likely. Prevention. Carrier control. Early detection and treatment of patients. LECTURE No. 23. Type Arthropods 1. Diversity and morphology of arthropods More than 1 million species belong to Arthropoda arthropods. Representatives of the classes Arachnida (they are studied by arachnology) and Insects (they are studied by entomology), whose pathogenic action is studied by the section of medical parasitology - arachnoentomology, are of the greatest medical importance. Among the representatives of these classes there are permanent and temporary human parasites, intermediate hosts of other parasites, carriers of infectious and parasitic diseases, species poisonous and dangerous to humans (scorpions, spiders, etc.). The class Crustaceans contains only some species that are intermediate hosts for some helminths (for example, flukes). Aromorphoses of the Arthropod type: 1) external skeleton; 2) jointed limbs; 3) striated muscles; 4) isolation and specialization of muscles. The phylum Arthropods includes the subtypes Gill-breathers (the class Crustacea is of medical importance), Chelicerae (the class Arachnids) and Tracheal-breathers (the class Insects). In the class Arachnids, representatives of the orders Scorpions (Scorpiones), Spiders (Arachnei) and Ticks (Acari) are of medical importance. Morphology Arthropods are characterized by a three-layer body, i.e., development from three germ layers. There is bilateral symmetry and heteronomous articulation of the body (body segments have different structures and functions). The presence of metamerically arranged jointed limbs is characteristic. The body consists of segments that form three sections - the head, chest and abdomen. Some species have a single cephalothorax, while others merge all three sections. Jointed limbs work on the principle of a lever. There is an outer chitinous cover, which performs a protective role and is designed to attach muscles (external skeleton). Due to the inextensibility of the chitinized cuticle, the growth of arthropods is associated with molting. In higher crustaceans, chitin is impregnated with calcium salts, in insects - with proteins. The body cavity, the mixocoel, is formed as a result of the fusion of the primary and secondary embryonic cavities. Characterized by the presence of the digestive, excretory, respiratory, circulatory, nervous, endocrine and reproductive systems. The digestive system has three sections - anterior, middle and posterior. Ends with an anus. In the middle section there are complex digestive glands. The anterior and posterior sections have a cuticular lining. The presence of a complexly arranged oral apparatus is characteristic. The excretory system in different species is built differently. It is represented by modified metanephridia (green or coxal glands) or malpighian vessels. The structure of the respiratory organs depends on the environment where the animal lives. In aquatic representatives, these are gills, in terrestrial species, saccular lungs or tracheas. The gills and lungs are modified limbs, the trachea are protrusions of the integument. The circulatory system is not closed. On the dorsal side of the body there is a pulsating heart. Blood carries only nutrients, not oxygen. The nervous system is built from the head ganglion, peripharyngeal commissures and the ventral nerve cord from partially fused nerve ganglions. The largest ganglia - sub-pharyngeal and supra-pharyngeal - are located at the anterior end of the body. The sense organs are well developed - smell, touch, taste, sight, hearing, balance organs. There are endocrine glands, which, like the nervous system, play a regulatory role. Most representatives of the type have separate sexes. Sexual dimorphism is pronounced. Reproduction is only sexual. Development is direct or indirect, in the latter case - with complete or incomplete metamorphosis. 2. Ticks They belong to the subtype Cheliceraceae, class Arachnids. Representatives of this order have an unsegmented body of an oval or spherical shape. It is covered with chitinous cuticle. There are 6 pairs of limbs: the first 2 pairs (chelicerae and pedipalps) are close together and form a complex proboscis. Pedipalps also function as organs of touch and smell. The remaining 4 pairs of limbs serve for movement, these are walking legs. The digestive system is adapted to eating semi-liquid and liquid foods. In this regard, the pharynx of arachnids serves as a sucking apparatus. There are glands that produce saliva that hardens when a tick bites. The respiratory system consists of leaf-shaped lungs and tracheas, which open on the lateral surface of the body with holes - stigmas. The tracheae form a system of branched tubes that fit all organs and carry oxygen directly to them. The circulatory system in ticks is built the least simple compared to other arachnids. They either do not have it at all, or consist of a sac-shaped heart with holes. The nervous system is characterized by a high concentration of its constituent parts. In some species of ticks, the entire nervous system merges into one cephalothoracic ganglion. All arachnids are dioecious. At the same time, sexual dimorphism is quite pronounced. The development of ticks proceeds with metamorphosis. A sexually mature female lays eggs, from which larvae hatch, having 3 pairs of legs. Also, they do not have stigmas, trachea and genital opening. After the first molt, the larva turns into a nymph, which has 4 pairs of legs, but, unlike the adult stage (imago), it still has underdeveloped gonads. Depending on the type of tick, one nymphal stage or several can be observed. After the last molt, the nymph turns into an imago. Among ticks there are free-living species that are predators. There are species that are parasites of humans, animals and plants. Many diseases of cultivated plants are caused by various types of mites. Some ticks have adapted to living in human habitation. These are house mites. Other mites have adapted to temporary ectoparasitism (ie, living on the surface of the body of humans and other animals). However, they still spend most of their lives in their natural habitat, so these species have not undergone deep degeneration of the structure. These include representatives of the families Iksodovye and Argazovye. A small part of the species has adapted to constant parasitism on humans. It was they who underwent the most profound degeneration of the structure and adaptation to parasitism. These include scabies itch (the causative agent of scabies) and acne gland, which lives in the sebaceous glands and skin follicles. Scabies itch Scabies itch (Sarcoptes scabiei) is the causative agent of human scabies (scabies). Refers to permanent human parasites, in whose body it lives in the stratum corneum of the epidermis. The disease is ubiquitous, as the parasite is inextricably linked with humans. Close species can also cause scabies in domestic and wild animals, but they do not have strict specificity with respect to the host, therefore, scabies of dogs, cats, horses, pigs, sheep, goats, etc. can parasitize on humans. They do not live long, but cause characteristic changes in the skin. The size of the parasite is microscopic: the length of the female is up to 0,4 mm, the male is about 0,3 mm. The whole body is covered with bristles of different lengths, there are suction cups on the limbs. The limbs are greatly reduced. The oral apparatus is adapted to gnaw through passages in the human skin, where the female lays eggs (up to 50 pieces in a lifetime, which lasts up to 15 days). Metamorphosis also takes place here (in 1-2 weeks). To penetrate the skin, the parasite chooses the most tender places: interdigital spaces, genitals, armpits, abdomen. The length of the move that the female makes reaches 2-3 mm (males do not make moves). When the mites move in the thickness of the skin, they irritate the nerve endings, which causes unbearable itching. Tick activity intensifies at night. When combing, the passages of ticks are opened. Larvae, eggs and adult mites are dispersed over the patient's underwear and surrounding objects, which can contribute to the infection of healthy individuals. You can become infected with scabies when using personal clothing, bedding and things of a sick person. Diagnostics The lesions of these mites are very characteristic. On the skin, straight or twisted strips of an off-white color are found. At one end you can find a vial in which the female is located. Its contents can be transferred to a glass slide and microscoped in a drop of glycerol. Prevention Compliance with the rules of personal hygiene, maintaining cleanliness of the body. Early detection and treatment of patients, disinfection of their linen and personal belongings, health education. Sanitary supervision of hostels, public baths, etc. Acne iron Acne gland (Demodex folliculorum) - the causative agent of de-modecosis. It lives in the sebaceous glands, hair follicles of the skin of the face, neck and shoulders, located in groups. In weakened people prone to allergies, the parasite can actively multiply. In this case, blockage of the ducts of the glands occurs and a massive acne develops. In healthy people with good immunity, the disease may be asymptomatic. The resettlement of the parasite occurs when using common linen and personal hygiene items. Diagnostics The extruded contents of the gland or hair follicle are microscoped on a glass slide. You can find an adult parasite, larva, nymphs and eggs. Prevention Compliance with the rules of personal hygiene. Treatment of the underlying disease that causes a weakening of the immune system. Identification and treatment of patients. 3. Ticks - inhabitants of human dwellings These ticks have adapted to living in human dwellings, where they find food for themselves. Representatives of this group of mites are very small, usually less than 1 mm. Gnawing mouth apparatus: chelicerae and pedipalps are adapted to capture and grind food. These ticks can actively move around human habitation in search of food. This group of mites includes flour and cheese mites, as well as the so-called house mites - permanent inhabitants of the human home. They feed on food reserves: flour, grain, smoked meat and fish, dried vegetables and fruits, desquamated particles of human epidermis, mold spores. All these types of ticks can pose a certain danger to humans. Firstly, they can penetrate with air and dust into the human respiratory tract, where they cause the disease acariasis. Appear cough, sneezing, sore throat, often recurrent colds and repeated pneumonia. In addition, ticks of this group can enter the gastrointestinal tract with spoiled food products, causing nausea, vomiting, and upset stools. Some species of these ticks have adapted to living in the anoxic environment of the large intestine, where they can even multiply. Ticks that eat food spoil it and make it inedible. By biting a person, they can cause the development of contact dermatitis (skin inflammation), which are called grain scabies, grocers' scabies, etc. Measures to combat mites that live in food products consist in lowering the humidity and temperature in the rooms where they are stored, since these factors play an important role in the development and reproduction of mites. Of particular interest in recent times is the so-called house tick, which has become a permanent inhabitant of most human homes. It lives in house dust, mattresses, bed linen, sofa cushions, curtains, etc. The most famous representative of the group of house mites is Dermatophagoi-des pteronyssinus. It has extremely small dimensions (up to 0,1 mm). In 1 g of house dust, from 100 to 500 individuals of this species can be found. In the mattress of one double bed, a population of up to 1 individuals can live simultaneously. The pathogenic effect of these mites is that they cause severe allergization of the human body. In this case, allergens of the chitinous cover of the body of the tick and its feces are of particular importance. Studies have shown that house dust mites play a major role in the development of asthma. In addition, they can cause the development of contact dermatitis in people with hypersensitivity of the skin. The fight against house dust mites consists in the most frequent wet cleaning of the premises, the use of a vacuum cleaner. It is recommended to replace pillows, blankets, mattresses made of natural materials with synthetic ones, in which ticks cannot live. 4. Family Ixodid ticks All ixodid ticks are temporary blood-sucking ectoparasites of humans and animals. The temporary host on which they feed is called the host-feeder. These are rather large mites (their size is up to 2 cm, depending on the degree of saturation). A characteristic feature of these ticks is that the integuments of the body and the digestive system of the female are highly extensible. This allows them to eat rarely (sometimes once in a lifetime), but in large quantities. The oral apparatus is adapted for piercing the skin and sucking blood. The proboscis has a hypostome: a long flattened outgrowth on which sharp, backward-directed teeth are located. The chelicerae are serrate on the sides. With their help, a wound is formed on the host's skin, into which the hypostome is immersed. When bitten, saliva is injected into the wound, which freezes around the proboscis. So the tick can tightly attach to the host's body and live on it for a long time (sometimes up to 1 month). In females, the chitinous shield covers no more than half of the body surface, so they can absorb a significant amount of blood. Males are completely covered with an inextensible chitinous shield. Ixodid ticks have significant fecundity, which resists their mass death during starvation and the absence of a host. After feeding, the female lays up to 20 eggs in the ground (burrows of small rodents, soil cracks, forest litter). But only a small number of them survive to sexual maturity. A larva hatches from the egg, which usually feeds once on small mammals (rodents, insectivores). Then the well-fed larva falls to the ground, molts and turns into a nymph. It is larger than the previous stage and feeds on hares, squirrels, rats. After molting, it turns into a sexually mature individual - an imago. An adult tick sucks the blood of large domestic and wild mammals (foxes, wolves, dogs) and humans. Most often, a tick changes three hosts during development, on each of which it feeds only once. Many ixodid ticks passively lie in wait for their owners, but in places where the meeting is most likely: at the ends of branches at a height of up to 1 m along the paths where animals move. However, some species are able to make active search movements. Many ixodid ticks are carriers of pathogens of dangerous diseases in humans and animals. Among these diseases, tick-borne spring-summer encephalitis (this is a viral disease) is the most famous. Viruses multiply in the body of the tick and accumulate in the salivary glands and ovaries. When bitten, viruses enter the wound (transmissible transmission of the virus occurs). When laying eggs, viruses are transmitted to subsequent generations of ticks (transovarial transmission - through eggs). Among ixodid ticks, the following species are important as carriers and natural reservoirs of diseases: taiga tick (Ixodes persulcatus), dog tick (Ixodes ricinus), ticks of the genus Dermatocenter (pasture tick) and Hyalomma 5. Representatives of the Ixodid tick family. Morphology, pathogenic significance The length of the pliers is 1-10 mm. About 1000 species of ixo-dove ticks have been described. Fertility - up to 10, in some species - up to 000 eggs. They are carriers of pathogens of tick-borne encephalitis, tick-borne typhus, tularemia, hemorrhagic fever, Q fever, and piroplasmosis in domestic animals. dog tick The dog tick (Ixodes ricinus) is found throughout Eurasia in mixed and deciduous forests and shrubs. Supports the existence in nature of foci of tularemia among rodents, from which the disease is transmitted to humans and domestic animals. The body of the mite is oval, covered with an elastic cuticle. Males reach a length of 2,5 mm, their color is brown. The hungry female also has a brown body. As it becomes saturated with blood, the color changes from yellow to reddish. The length of a hungry female is 4 mm, well-fed - up to 11 mm in length. On the dorsal side there is a shield, which in males covers the entire dorsal side. In females, larvae and nymphs, the chitinous shield is small and covers only a portion of the anterior part of the back. On the rest of the body, the covers are soft, which makes it possible to significantly increase the volume of the body when absorbing blood. The development cycle is long - up to 7 years. The dog tick parasitizes many wild and domestic animals (including dogs) and humans; sticks to the owner for several days. In addition to being a carrier of the causative agent of tularemia, it also causes a local irritant effect by biting the host. When the wound becomes infected, severe purulent complications may occur due to the addition of a bacterial infection. taiga tick The taiga tick (Ixodes persulcatus) is distributed in the taiga zone of Eurasia from the Far East to the mountains of Central Europe (including the European part of Russia). It is a carrier of the causative agent of a severe viral disease - taiga tick-borne encephalitis. This species is the most dangerous for humans, as it attacks him more often than others. In morphology, the taiga tick is similar to the dog tick. It differs only in some structural features and a shorter development cycle (2-3 years). The taiga tick parasitizes many mammals and birds, which keeps the encephalitis virus circulating. The main natural reservoir of the taiga encephalitis virus are chipmunks, hedgehogs, voles and other small rodents and birds. Of domestic animals, ticks most often attack goats. This is due to the peculiarities of the eating behavior of goats: they prefer to wade through the bush. At the same time, ticks get on their fur. Goats themselves suffer from tick-borne encephalitis in a mild form, but transmit the virus to humans with milk. Thus, the tick-borne encephalitis virus is characterized by transmissible (through a tick-borne vector during blood-sucking) and transovarial (by a female through eggs) transmission routes. Other ixodid ticks Representatives of the genus Derma-tocenter inhabit the steppe and forest zones. Their larvae and nymphs feed on the blood of small mammals (mainly rodents). Dermatocenter pictus (inhabits deciduous and mixed forests) and Dermatocenter marginatus (inhabits the steppe zone) are carriers of the tularemia pathogen. In the body of ticks, pathogens live for years, so foci of the disease still exist. Dermatocenter marginatus also carries the brucellosis pathogen, which affects small and large cattle, pigs and humans. Dermatocenter nuttalli (inhabits the steppes of Western Siberia and Transbaikalia) supports the existence in nature of foci of tick-borne typhus (pathogen - spirochetes). 6. Representatives of the family Argas mites. Morphology, development cycle Representatives of the family Argas mites are inhabitants of natural and artificial enclosed spaces. They settle in burrows and lairs of animals, caves, residential and non-residential buildings (mainly made of clay). Ticks are distributed mainly in countries with a warm and hot climate, often found in the Transcaucasus and Central Asia. Unlike ixodid ticks, the mouthparts of argas ticks are located on the ventral side of the body and do not project forward. There is no chitinous shield on the dorsal side. Instead, there are numerous chitinous tubercles and outgrowths, so the outer integument of the body is highly extensible. A wide welt runs along the edge of the body. The length of hungry ticks is 2-13 mm. The living conditions of these ticks are more favorable than those of the ixodid, so they do not die in such numbers. In this regard, females lay fewer eggs (up to 1000, in one clutch - up to 200). During their life, parasites feed several times and each time on a new host. This is due to the fact that animals rarely visit the habitat of these ticks. Sucking lasts from 3 to 30 minutes. Since the female's diet is not so plentiful, her eggs mature less. But argas mites are able to lay them several times throughout their lives. The shelter of these ticks may not be visited by the owners for a very long time, so the ticks may not feed for years - up to 11 years, using the blood supplies that they received from the previous owner. In this regard, the development cycle can be delayed for a long time - up to 20-28 years. In the cycle of development of argas mites, several generations of nymphs change: nymph 1, nymph 2, nymph 3 (sometimes more), and only then follows the imago. If the host does not appear in the shelter at any phase, development is suspended. The settlement of new shelters is very slow. A typical representative is the village tick (Ornithodorus papillipes). It is a carrier of pathogens of tick-borne recurrent encephalitis - spirochetes of the genus Borrelia. Spirochetes multiply in the intestines of ticks, and then penetrate into all internal organs (including the ovaries), which is important for the transovarial transmission of spirochetes to subsequent generations of ticks. The entry of spirochetes into the human body occurs through the proboscis when bitten, as well as when feces and tick excretion products get on the skin. The village mite has a dark gray color. The length of the female is 8 mm, the male is up to 6 mm. It feeds on rodents, bats, larks, as well as domestic animals - dogs, cattle, horses, cats, etc. Adults can starve up to 15 years. Prevention of tick-borne relapsing encephalitis. 1. Personal. Protection against tick attacks: do not sleep or lie in caves and buildings where ticks are suspected to be, use individual repellents against these parasites. 2. Public. Destruction of ticks and rodents that are their carriers, demolition and burning of old adobe premises inhabited by ticks. LECTURE No. 24 1. Morphology, physiology, systematics The class Insects is the most numerous class of animals and has more than 1 million species. The body of insects is divided into three sections: head, thorax and abdomen. The integuments of the body are represented by a single layer of hypodermal cells, which secrete organic matter, chitin, on their surface. Chitin forms a dense shell that protects the body of insects, and also serves as a place for attachment of muscles, performing the function of the external skeleton. On the head of insects there are sensory organs - antennae and eyes, as well as a complex oral apparatus, the structure of which depends on the method of nutrition: gnawing, licking, sucking, piercing-sucking, etc. The chest of insects includes three segments, each of which bears one pair of walking legs, the structure of which is different in different species and depends on the mode of movement and motor activity. The limbs lying near the mouth opening bear tactile bristles, which act as an olfactory organ, serve to capture and grind food. The abdomen has no limbs. In addition, most free-living insects have two pairs of wings on their chests. The musculature of insects is well developed and consists of striated muscle fibers that form individual muscles. The CNS consists of the head ganglion, the parapharyngeal nerve ring, and the ventral nerve cord. The body cavity in insects is mixed (myxocoel), formed by the fusion of the primary and secondary body cavities. The respiratory organs of insects are the trachea. The digestive organs consist of the anterior, middle and hindgut. The anterior and posterior intestines have a chitinous lining. The foregut is divided into the pharynx, goiter and chewing stomach. The midgut is used for digestion and absorption of food. The excretory organs are represented by Malpighian vessels lying in the body cavity and opening into the intestine at the border of the middle and hind intestines. The circulatory system is open and does not perform the function of gas exchange. Insects have a heart on the dorsal side, consisting of several chambers equipped with valves. Insects are dioecious animals. The development of insects occurs with metamorphosis - incomplete, when a larva similar to an adult hatches from an egg, or complete, when ontogenesis includes the pupal stage. Insects of medical importance are divided into: 1) synanthropic species that are not parasites; 2) temporary blood-sucking parasites; 3) permanent blood-sucking parasites; 4) tissue and cavity larval parasites. Features of insects that contributed to their wide distribution: 1) the ability to fly, allowing you to quickly explore new territories; 2) greater mobility and variety of movements associated with developed muscles; 3) chitinous cover, which primarily performs a protective function; 4) a variety of methods of reproduction (sexual reproduction, parthenogenesis of various species); 5) high fertility and ability to mass reproduction; 6) a variety of ways of postembryonic development; 7) high survival rate. 2. Squad Lice There are two types of lice that parasitize humans: the human louse and the pubic louse. The human louse is represented by two subspecies: the head louse and the body louse. The body louse is found in countries with a cold and temperate climate. The pubic louse is less common, but common in all climatic zones. She lives on the pubis, in the armpits, less often - on the eyebrows, eyelashes, in the beard. The presence of body lice and head lice in humans is called pediculosis, parasitism of the pubic lice is called phthiriasis. Common features for all types of lice are small size, a simplified development cycle (development with incomplete metamorphosis), limbs adapted for fixation on the skin, hair and clothing of a person, a piercing-sucking oral apparatus; wings are missing. Clothes louse - the largest, reaches sizes up to 4,7 mm. Body lice and head lice have a clearly demarcated head, thorax, and abdomen. In the pubic louse, the chest and abdomen have merged. Clothes louse lives for about 50 days, head louse - up to 40, and pubic - up to 30. Head and body lice feed on human blood 2-3 times a day, and pubic - almost continuously, in small portions. Female body lice and head lice lay up to 300 eggs in their lifetime, pubic lice - up to 50 eggs. Lice eggs (the so-called nits) are small, oblong, white in color, fixed on the hair or fibers of clothing. They are very resistant to mechanical and chemical influences. Lice saliva is toxic. At the site of a louse bite, it causes a feeling of itching and burning, in some people it can cause allergic reactions. Small punctate hemorrhages (petechiae) remain at the site of the bites. Itching at the site of the bite causes a person to scratch the skin until abrasions form, which can become infected and fester. In this case, the hair on the head sticks together, tangles, and a tangle is formed. The pubic louse is only a parasite and does not carry disease. Head and body lice are specific carriers of pathogens of relapsing and epidemic typhus, Volyn fever. The causative agents of relapsing fever multiply and mature in the body cavity of the lice, human infection occurs when the lice are crushed and their hemolymph enters the bite wound or abrasions after scratching. The causative agents of epidemic typhus and Volyn fever multiply in the thickness of the intestinal wall of lice, being released into the external environment with feces. Human infection with these diseases occurs when lice feces with pathogens enter skin defects or mucous membranes of the eyes and respiratory tract. Prevention Compliance with the rules of personal hygiene, especially in crowded places. For treatment, external and internal means are used: ointments and shampoos containing insecticides, as well as drugs taken orally. In the fight against already existing pediculosis, linen is processed in disinfection chambers and the hair of patients is cut short. 3. Flea Squad All representatives of the Flea order are characterized by small body sizes (1-5 mm), its flattening from the sides, which facilitates movement among the hair of the host animal, and the presence of bristles on the surface of the body growing in the direction from front to back. The hind legs of fleas are elongated, jumping. The tarsi of all legs are five-membered, well developed, ending in two claws. The head is small, on the head there are short antennae, in front of which there is one simple eye. The oral apparatus of fleas is adapted for piercing the skin and sucking the blood of the host animal. The skin is pierced with serrated mandibles. The stomach of fleas can grow significantly. Male fleas are smaller than females. Fertilized females forcefully eject eggs in portions of several pieces so that the eggs do not remain on the animal's fur, but fall to the ground in its hole. A legless, but very mobile, worm-like larva with a well-developed head emerges from the egg. For further development, the larva needs sufficient moisture, so it burrows into the ground or debris in the host's nest or burrow. The larva feeds on decaying organic debris, including the remains of undigested blood contained in the feces of adult fleas. Fleas are insects with complete metamorphosis. The grown larva surrounds itself with a web cocoon, covered with dust and grains of sand on the outside, and pupates in it. The pupa of fleas is typical free. The adult flea, emerging from the pupa, watches over the host animal. In connection with the parasitic way of life, fleas lack wings, the organ of vision is reduced. The most famous representatives of the Flea squad are the rat flea and the human flea. These species feed on the blood of rats and humans, respectively, but in the absence of their hosts they can parasitize any other animals. The rat flea lives in rat holes, the human flea lives in hard-to-reach places in human dwellings (in crevices, floor cracks, behind baseboards). In their habitats, female fleas lay eggs, which then develop into worm-like larvae. For some time they feed on organic matter, including the feces of adult fleas, after 3-4 weeks they pupate and turn into adult fleas. Fleas bite humans at night. Toxic substances in their saliva cause intense itching. Fleas are carriers of plague pathogens. They bite the host animal and suck up the plague bacteria along with the blood. In the stomach of a flea, bacteria multiply very actively, forming a plug of plague sticks - a plague block. Due to the fact that the cork occupies the entire volume of the flea's stomach, new portions of blood no longer fit. A hungry flea makes repeated bloodsucking attempts. When biting a healthy animal or person, the first thing a flea does is burp a plague plug into the wound. A large number of pathogens enter the host's blood, which is facilitated by combing the bite site. Rats, ground squirrels, ferrets, etc. serve as natural reservoirs of plague. Rodents are also sources of other infections: tularemia, rat typhus. 4. Features of the developmental biology of mosquitoes of the genus Anopheles, Aedes, Culex For mosquitoes (order Diptera, suborder Long-whiskers), characteristic external features are a thin body, long legs and a small head with a proboscis-type mouth apparatus. Mosquitoes are ubiquitous, especially in warm, humid climates. Mosquitoes are carriers of over 50 diseases. Mosquitoes - representatives of the genera Culex and ncdcs (non-malarial) are carriers of pathogens of Japanese encephalitis, yellow fever, anthrax, representatives of the genus nnopheles (malarial mosquitoes) - carriers of malarial plasmodium. Nonmalarial and malarial mosquitoes differ from each other at all stages of the life cycle. All mosquitoes lay their eggs in water or moist soil near bodies of water. Eggs of mosquitoes of the genus nnopheles are located on the surface of the water one at a time, each egg has two air floats. Their larvae are located under water parallel to its surface, on the penultimate segment they have two respiratory openings. The pupae are comma-shaped, develop under the surface of the water and breathe oxygen through breathing horns in the form of wide funnels. Adult mosquitoes of the genus nnopheles, sitting on objects, raise the body up, and hold the head down, forming an acute angle with the surface. On both sides of their proboscis are mandibular palps equal in length to it. Mosquitoes of the genera Culex and Aedes lay eggs in groups in the water. Larvae in water lie at an angle to its surface and have a long respiratory siphon on the penultimate segment. The pupae also have the appearance of a comma, but their respiratory horns are shaped like thin cylindrical tubes. The mandibular palps of adult mosquitoes barely reach a third of the length of the proboscis. Sitting on objects, mosquitoes keep the body parallel to their surface. The malarial mosquito is the definitive host, while humans are the intermediate host of the protozoan malarial plasmodium (a type of sporozoan). The development cycle of malarial plasmodium consists of three parts: 1) schizogony - asexual reproduction by multiple division; 2) gametogony - sexual reproduction; 3) sporogony - the formation of forms specific for sporozoans (sporozoites). Piercing the skin of a healthy person, an invasive mosquito injects into his blood saliva containing sporozoites, which are introduced into gametocytes in the liver cells. There they turn first into trophozoites, then into schizonts. Schizonts divide by schizogony to form merozoites. This stage of the cycle is called preerythrocytic schizogony and corresponds to the incubation period of the disease. The acute period of the disease begins with the introduction of merozoites into erythrocytes. Here, merozoites also turn into trophozoites and schizonts, which divide schizogony to form merozoites. The erythrocyte membranes rupture and the merozoites enter the bloodstream and invade new erythrocytes, where the cycle repeats anew for 48 or 72 hours. When erythrocytes rupture, along with merozoites, toxic metabolic products of the parasite and free heme enter the bloodstream, causing attacks of malarial fever. Part of the merozoites turns into immature germ cells - gametocytes. Gamete maturation is possible only in the body of a mosquito. LECTURE No. 25. Poisonous animals 1 Poisonous Arachnids The class Arachnids includes spiders, scorpions, phalanges, ticks. Poisonous arachnids include spiders such as tarantula and karakurt, as well as all scorpions. Poisonous arachnids feed on live prey, mostly insects. By piercing the chitinous integuments of the insect with their chelicerae, the spiders inject the poison inside along with the digestive juices, which provide partial digestion of the prey outside the spider's body and facilitate its suction. Thus, the digestion of spiders is mixed, external-internal. Scorpions paralyze their prey with the help of poison from special glands located on their tail - the last abdominal segment (in scorpions, both the chest and abdomen are divided into segments). Scorpio squad There are more than 1500 species of scorpions in the world, of which 13-15 species are found in Russia. Scorpions of different species live both in places with a humid climate and in sandy deserts. Scorpions are nocturnal animals. Scorpions feed on spiders, harvestmen, centipedes and other invertebrates and their larvae, using poison only to immobilize the victim. With a long absence of food, scorpions cannibalize. A female scorpion gives birth to 15-30 cubs at a time. Freed from the membranes, the cubs climb onto the mother's body in 20-30 minutes and remain there for 10-12 days. The structure of the poisonous apparatus of scorpions. On the jointed flexible metasome (tail) there is an anal lobe ending in a poisonous needle. The size of the needle and its shape vary in different species. In the anal lobe are two poisonous glands, the ducts of which open near the top of the needle with two small holes. Each gland is oval in shape and gradually narrows posteriorly into a long excretory duct that runs inside the needle. The walls of the gland are folded, and each gland is surrounded from the inside and from above by a thick layer of transverse muscle fibers. When these muscles contract, the secret is thrown out. Squad Spiders About 27 species belong to the order Spiders, most of which have a poisonous apparatus. The most dangerous for humans in Russia are karakurt and tarantula. The structure of the poisonous apparatus. The front pair of limbs of chelicera spiders is designed to protect and kill prey. Chelicerae are located in front of the mouth on the ventral side of the cephalothorax and look like short but powerful two-segmented appendages. The considered representatives of the group of poisonous spiders are characterized by the vertical arrangement of the main segments of the chelicerae perpendicular to the main axis of the body. Thick basal segment of chelicera markedly thickened. At its apex, at the outer edge, it is articulated with a sharp, claw-like, curved terminal segment, which moves only in one plane and can fold like a knife blade into a furrow on the basilar segment. The edges of the groove are armed with chitinous teeth. At the end of the claw-shaped segment, the ducts of two poisonous glands open, lying either in the main segments, or entering the cephalothorax. Poison glands are represented by large cylindrical sacs with a characteristic striation, which depends on the presence of an external muscular mantle and oblique spiral fibers. Thin excretory streams depart from the anterior ends of the glands. 2 Poisonous Vertebrates There are about 5000 species of venomous vertebrates. They contain in the body constantly or periodically substances that are toxic to individuals of other species. In small doses, poison that has entered the body of another animal causes painful disorders, in large doses - death. Some types of poisonous animals have special glands that produce poison, others contain toxic substances in certain organs and tissues. Some species have a wounding apparatus that contributes to the introduction of poison into the body of an enemy or victim. In many animals (snakes) the venom glands are associated with the mouth organs, and the poison is injected into the victim's body when bitten or stabbed in case of defense or attack. In vertebrates that have poisonous glands, but do not have a special apparatus for introducing poison into the body of the victim, for example, amphibians (salamanders, newts, toads), the glands are located in different parts of the skin; when the animal is irritated, the poison is released onto the surface of the skin and acts on the mucous membranes of the predator. poisonous fish About 200 species of fish are known to have poisonous spines or spikes. Poisonous fish are divided into active-poisonous and passive-poisonous. Actively poisonous fish usually lead a sedentary lifestyle, watching for their prey. One of the most dangerous poisonous fish - the stingray - is found along the entire coast of the oceans. Fishermen, scuba divers and just swimmers most often suffer from stingray injections. However, stingrays almost never use their spike to attack. The injection causes severe pain, weakness, loss of consciousness, diarrhea, convulsions, respiratory failure. An injection in the chest or abdomen can be fatal. Poisonous amphibians: salamanders, toads, frogs Amphibians that live in tropical climates are more often poisonous. In the jungles of South America there is a frog - coca, whose poison is the most powerful of the known organic poisons. poisonous reptiles Poisonous snakes are characterized by the presence of poisonous teeth and glands that produce poison. Poison glands are paired and located on both sides of the head behind the eyes, covered with temporal muscles. Their excretory canals open at the base of the poisonous teeth. According to the shape and arrangement of teeth, snakes are conditionally divided into three groups. 1. Smooth-toothed (snakes, snakes). Not poisonous. The teeth are homogeneous, smooth, devoid of channels. 2. Back furrowed (cat and lizard snakes). The venomous teeth are located at the posterior end of the upper jaw with a groove on the posterior surface. At the base of the groove, the duct of the gland that produces the poison opens. They do not pose a particular danger to humans, since their poisonous teeth are located deep in the mouth; these snakes cannot inject their poison into a person. 3. Anterior furrowed (viper, cobra). Poisonous teeth are located in the anterior part of the upper jaw. On the front surface there are grooves for the drain of poison. Bites lead to poisoning of the body, often dangerous to human life. The teeth of venomous snakes are movable and in the closed mouth lie longitudinally above the tongue. When opening the mouth, they rise and take a vertical position in relation to the jaw. When biting, the teeth pierce into the prey. The snake rushes forward to free itself. As a result, a space is formed between the affected area and the teeth, sufficient for the drain of the poison. LECTURE No. 26. Ecology 1. Subject and tasks of ecology Ecology is the science of the relationship of organisms, communities with each other and with the environment. Tasks of ecology as a science: 1) the study of the relationship of organisms and their populations with the environment; 2) study of the effect of the environment on the structure, vital activity and behavior of organisms; 3) establishing the relationship between the environment and population size; 4) study of relationships between populations of different species; 5) the study of the struggle for existence and the direction of natural selection in a population. Human ecology is a complex science that studies the patterns of human interaction with the environment, population issues, the preservation and development of health, and the improvement of a person's physical and mental capabilities. The human habitat, in comparison with the habitat of other living beings, is a very complex interweaving of interacting natural and anthropogenic factors, and this set differs sharply in different places. Humans have 3 habitats: 1) natural; 2) social; 3) technogenic. The criterion for the quality of the human environment is the state of his health. Unlike all other creatures, a person has a dual nature from the point of view of ecology: on the one hand, a person is an object of various environmental factors (sunlight, other creatures), on the other hand, a person himself is an ecological (anthropogenic) factor. 2. General characteristics of the human environment. Ecological crisis The environment is a set of factors and elements that affect the organism in its habitat. Any living being lives in conditions of constant change in environmental factors, adapting to them and regulating its life activity in accordance with these changes. Living organisms exist as mobile systems open to the flow of energy and information from the environment. On our planet, living organisms have mastered four main habitats, each of which is distinguished by a combination of specific factors and elements that affect the body. Life arose and spread in the aquatic environment. Subsequently, living organisms came to land, took possession of the air, populated the soil. The natural environment represents human living conditions and resources for life. The development of human economic activity improves the conditions of his existence, but requires an increase in the expenditure of natural, energy and material resources. In the course of industrial and agricultural production, waste is generated, which, together with the production processes themselves, disrupt and pollute biogeocenoses, gradually worsening human living conditions. Biological factors, or the driving forces of evolution, are common to the whole of living nature, including human beings. They include hereditary variability and natural selection. The adaptation of organisms to the effects of environmental factors is called adaptation. The ability to adapt is one of the most important properties of living things. Only adapted organisms survive, acquiring traits useful for life in the process of evolution. These signs are fixed in generations due to the ability of organisms to reproduce. Ways of human impact on nature. Ecological crisis Man as an anthropogenic factor has a huge impact on nature. Changes in the environment as a result of the impact of anthropogenic factors: 1) change in the structure of the earth's surface; 2) change in the composition of the atmosphere; 3) change in the circulation of substances; 4) changes in the qualitative and quantitative composition of flora and fauna; 5) greenhouse effect; 6) noise pollution; 7) military actions. Irrational human activity has led to violations of all components of the biosphere. Atmosphere The main sources of pollution are cars and industrial enterprises. Every year, 200 million tons of carbon monoxide and carbon dioxide, 150 million tons of sulfur oxides, and 50 million tons of nitrogen oxides are emitted into the atmosphere. In addition, a large number of fine particles are emitted into the atmosphere, forming the so-called atmospheric aerosol. Due to the combustion of coal, mercury, arsenic, lead, cadmium enter the atmosphere in quantities exceeding their involvement in the circulation of substances. A large amount of dust rises into the air in ecologically polluted areas, which detains 20-50% of sunlight. An increase in the concentration of carbon dioxide in the atmosphere, which has increased by 100% over the past 10 years, prevents thermal radiation into outer space, causing the greenhouse effect. Hydrosphere The main cause of pollution of the water basin is the discharge of untreated wastewater from industrial and municipal enterprises, as well as agricultural land. Washing into the rivers of mineral fertilizers and pesticides causes deterioration in the quality of drinking water and the death of many species of aquatic animals. The level of pollution of the World Ocean is increasing with river runoff, atmospheric precipitation, and oil production on the ocean shelf. A huge amount of lead, oil and oil products, household waste, pesticides gets into the water. Lithosphere The fertile soil layer is formed for a long time, and thanks to the cultivation of agricultural crops, tens of millions of tons of potassium, phosphorus and nitrogen, the main elements of plant nutrition, are annually withdrawn from the soil. Soil depletion does not occur if organic and mineral fertilizers are applied. If the plants are not fed and crop rotation is not observed, then the fertile layer is reduced to a minimum. Artificial irrigation of soils also has an adverse effect, since waterlogging or salinization of the surface layer of the soil most often occurs. Among the anthropogenic changes in the soil, erosion is of great importance - the destruction and demolition of the upper fertile soil layer. The K-700 tractor turns a layer of soil into dust in one season, the formation of which takes 5 years. There is wind and water erosion. Water erosion is the most destructive, it develops with improper cultivation of the land. Ecological crisis An ecological crisis is a violation of relationships within an ecosystem or irreversible phenomena in the biosphere caused by human activity. According to the degree of threat to human life and the development of society, an unfavorable ecological situation, an ecological disaster and an ecological catastrophe are distinguished. List of used literature 1. Kalyuzhny K. V. Handbook of biology. Rostov-on-Don: Phoenix, 2002. 2. Konstantinov V. M. General biology. Textbook. M.: Academy, 2004. 3. Pavlovsky E. N. Guide to human parasitology with the doctrine of carriers of vector-borne diseases. Moscow: Nauka, 1946. 4. Pimenova I. N., Pimenov A. V. Lectures on biology. Tutorial. Moscow: Lyceum, 2003. 5. Rzhevskaya R. A. Medical biology. Lecture notes. M.: Prior-publ., 2005. Authors: Kurbatova N.S., Kozlova E.A.
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