General biology. Cheat sheet: briefly, the most important

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General biology. Cheat sheet: briefly, the most important

Lecture notes, cheat sheets

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Table of contents

History of the development of cell theory
Life. Properties of living matter
Levels of life organization
cell composition
protein biosynthesis. Genetic code
General information about prokaryotic and eukaryotic cells
Functions and structure of the cytoplasmic membrane and cell nucleus
The structure and functions of mitochondria and lysosomes
The structure and functions of the endoplasmic reticulum, the Golgi complex
The structure and functions of non-membrane structures of the cell
Viruses. structure and reproduction. bacteriophages
Gametes. Properties, structure and functions of the egg and sperm
Fertilization
Reproduction. Asexual reproduction, its role and forms
Sexual reproduction. Its types, role. Atypical sexual reproduction
The life cycle of a cell. Concept, meaning and phases
Mitosis. Characteristics of the main stages. Atypical forms of mitosis
Meiosis, stages and meaning
Gametogenesis. Concept, stages
The concept of ontogenesis. Stages. Stages of embryonic development
G. Mendel's laws. Inheritance. Di- and polyhybrid crosses
Interactions of allelic genes. Dominance, co-dominance. Interallelic complementation. Inheritance of blood groups of the ABO system
non-allelic genes. Inheritance of sex-linked traits
Variability. Concept, Types. Mutations
Gene linkage and crossing over
Methods for studying human heredity
Biosphere. Definition. Components, the noosphere and its problems
ways of parasitism. Classification
Overview of protozoa. Their structure and activity
General characteristics of the sarcode class (rhizomes). Free-living and parasitic amoeba. Prevention
pathogenic amoeba. Structure, forms, life cycle
Class Flagellates. Structure and life
Trichomonas. Species, morphological characteristics. Diagnostics. Prevention
Giardia. Morphology. Vital activity of Leishmania. Forms. Diagnostics. Prevention
Trypanosomes (Tripanosoma). Kinds. Life cycle. Diagnostics. Prevention
General characteristics of the class Sporoviki
Toxoplasmosis: causative agent, characteristics, development cycle, prevention
Malarial Plasmodium: morphology, development cycle. Diagnostics. Prevention
Overview of the structure of ciliates. Balantidia. Structure. Diagnostics. Prevention
Type flatworms. characteristic features of the organization. General characteristics of the class flukes
Liver and feline flukes
Schistosomes
General characteristics of the class Tapeworms. Bull tapeworm
Dwarf pork tapeworm
Echinococcus and broad tapeworm. Diphyllobothriasis
Roundworms. Structural features. Ascaris human. Life cycle. Diagnostics. Prevention
Pinworm and whipworm
Trichinella and hookworm
Guinea worm. Biohelminths
Type Arthropods. Diversity and morphology
Ticks. Scabies pruritus and acne gland
Family Ixodid ticks. Dog taiga and other ticks
Class Insects. Morphology, physiology, systematics. Squad Vshi. Kinds. Prevention
Flea Squad. Features of the developmental biology of mosquitoes
Ecology
Poisonous animals. Arachnids. Vertebrates

1. History of the development of 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 has become 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. Life. Properties of living matter

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.

Properties of living structures:

1) self-updating. The basis of metabolism is balanced and clearly interconnected processes of assimilation (anabolism, synthesis, formation of new substances) and dissimilation (catabolism, decay);

2) self-reproduction. In this regard, living structures are constantly reproduced and updated, without losing their similarity with previous generations. 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;

5) maintenance of homeostasis - the relative dynamic constancy of the internal environment of the body, the physico-chemical parameters of the existence of the system;

6) structural organization - orderliness, of a living system, found in the study - biogeocenoses;

7) adaptation - the ability of a living organism to constantly adapt to changing conditions of existence in the environment;

8) reproduction (reproduction). Since life exists in the form of separate living systems, 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;

9) heredity. Provides continuity between generations of organisms (based on information flows). Due to heredity, traits are transmitted from generation to generation that provide adaptation to the environment;

10) variability - 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;

11) individual development (the process of ontogenesis) - the embodiment of the initial genetic information embedded in the structure of DNA molecules 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;

12) phylogenetic development. Based on progressive reproduction, heredity, struggle for existence and selection. As a result of evolution, a huge number of species appeared;

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.

3. 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.

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;

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 that is a self-functioning elementary

biological system. It is only at this level that the realization of genetic information and the processes of biosynthesis are possible;

4) tissue level. A set of cells with the same type of organization constitutes a tissue (EE);

5) organ level. Formed together with functioning cells belonging to different tissues (EE);

6) organismal (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) phenotype;

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 leads to evolutionarily significant changes (ES);

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, that is, a single planetary complex of biogeocenoses, different in species composition and characteristics of the abiotic (non-living) part;

10) nospheric level. This is an integral part of the biosphere, which is changed due to human activity.

4. Composition of the cell

All living systems contain chemical elements, both organic and inorganic, in varying proportions.

According to the quantitative content in the cell, all chemical elements are divided into 3 groups: macro-, micro- and ultramicroelements.

1. Macronutrients make up to 99% of the cell mass, of which up to 98% are 4 elements: oxygen, nitrogen, hydrogen and carbon.

2. Trace elements - mainly metal ions (cobalt, copper, zinc, etc.) and halogens (iodine, bromine, etc.). They are contained in amounts from 0,001% to 0,000001%.

3. 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 and.

The main organic compounds of the cell are proteins, fats, carbohydrates and nucleic acids.

Proteins are polymers whose monomers are amino acids. They are mainly composed of carbon, hydrogen, oxygen and nitrogen.

Protein functions:

1) protective;

2) structural;

3) motor;

4) spare;

5) transport;

6) receptor;

7) regulatory;

8) hormone proteins are involved in humoral regulation;

9) enzyme proteins catalyze all chemical reactions in the body;

10) energy.

Carbohydrates are mono- and polymers, which include carbon, hydrogen and oxygen in a ratio of 1: 2: 1.

Functions of carbohydrates:

1) energy;

2) structural;

3) storage.

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;

2) structural;

3) storage;

4) protective;

5) regulatory;

6) heat insulating.

The ATP (adenosine triphosphoric acid) molecule is formed in mitochondria and is the main source of energy.

5. Protein biosynthesis. Genetic code

Nucleic acids are phosphorus-containing biopolymers.

There are 2 types of nucleic acids - deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

DNA is a helix consisting of two complementary polynucleotide chains twisted to the right. Two chains of nucleotides are interconnected through nitrogenous bases according to the principle of complementarity: two hydrogen bonds arise between adenine and itimine, 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 (replication);

2) regulates all processes in the cell, providing the ability for transcription with subsequent translation.

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, with the help of 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.

RNA is a single stranded polymer. There are 3 types of RNA.

1. Messenger RNA (i-RNA) is located in the nucleus and cytoplasm of the cell, performs the function of transferring hereditary information from the nucleus to the cytoplasm of the cell.

2. Transfer RNA (t-RNA) is also found in the nucleus and cytoplasm of the cell, delivers amino acids to ribosomes during translation - protein biosynthesis.

3. Ribosomal RNA (r-RNA) is found in the nucleolus and ribosomes of the cell.

Protein biosynthesis occurs in several steps.

1. Transcription is the process of mRNA synthesis on a DNA template. An immature pro-mRNA is formed containing both coding and non-coding nucleotide sequences.

2. Then processing occurs - the maturation of the RNA molecule.

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.

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).

Terminator codons in i-RNA: UAA, UAG, UGA, in DNA: ATT, ATC, ACT.

The genetic code has characteristic properties.

1. Universality - the code is the same for all organisms.

2. Specificity - each codon codes for only one amino acid.

3. Degeneracy - most amino acids can be encoded by several codons.

6. General information about prokaryotic and eukaryotic cells

Prokaryotes have typical cellular stenosis.

Prenuclear prokaryotes do not have a typical nucleus. These include bacteria and blue-green algae.

Prokaryotes originated in the Archean era. These are very small cells ranging in size from 0,1 to 10 microns.

A typical bacterial cell is surrounded on the outside by a cell wall, the basis of which is the substance murein and determines the shape of the bacterial cell. On top of the cell wall there is a mucous capsule that performs a protective function.

Under the cell wall is the plasma membrane. The entire cell inside is filled with cytoplasm, which consists of a liquid part (hyaloplasm, or matrix), organelles and inclusions.

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, lamellae and lamelosomes are found - photosynthetic membranes. They contain the pigments chlorophyll and phycocyanin.

Some bacteria have organelles of movement - flagella. Bacteria have recognition organelles - pili (fimbriae).

The hyaloplasm also contains non-permanent inclusions: protein granules, fat drops, polysaccharide molecules, salts.

Each eukaryotic cell has a separate nucleus. The genetic material is concentrated mainly in the form of chromosomes, and consisting of DNA strands and protein molecules. Cell division occurs through mitosis (and for germ cells - meiosis). Eukaryotes include both unicellular and multicellular organisms.

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.

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. Proteins form the basis of nuclear juice (matrix). 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 general and special.

Organelles of general importance - endoplasmic reticulum, 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.

7. Functions and structure of the cytoplasmic membrane and cell nucleus

The elementary membrane consists of a bilayer of lipids in complex with proteins. 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.

Allocate peripheral proteins, integral (they are firmly embedded in the membrane. Functions of membrane proteins: receptor, structural, enzymatic, adhesive, antigenic, transport.

The most important function: promotes compartmentation - the division of the contents of the cell into separate cells that differ in the details of the chemical or enzymatic composition. This achieves a high orderliness of the internal contents of any eukaryotic cell.

Other features:

1) barrier (delimitation of the internal contents of the cell);

2) structural (giving a certain shape to cells);

3) protective (due to selective permeability);

4) regulatory (regulation of selective permeability for various substances);

5) adhesive function (all cells are interconnected through specific contacts (dense and loose);

6) receptor;

7) electrogenic (change in the electrical potential of the cell surface due to the redistribution of potassium and sodium ions); 8) antigenic: on the surface of each cell there are protein molecules. With their help, the immune system is able to distinguish between self and foreign cells. The nucleus is found in every eukaryotic cell. There may be one nucleus, or there may be several nuclei in a cell (depending on its activity and function).

The cell nucleus consists of a membrane, nuclear juice, nucleolus and chromatin. The nuclear envelope is made up of two membranes. The main functions of the nuclear membrane: the separation of genetic material (chromosomes) from the cytoplasm, as well as the regulation of bilateral relationships between the nucleus and the cytoplasm.

The nuclear envelope is permeated with pores that have a diameter of about 90 nm.

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.

The nucleolus is the structure where the formation and maturation of ribosomal RNA (rRNA) takes place. The rRNA genes occupy certain regions of several chromosomes, where nucleolar organizers are formed, in the region of which the nucleoli themselves are formed.

Chromatin consists mainly of DNA strands (40% of the mass of the chromosome) and proteins (about 60%), which together form the nucleoprotein complex.

8. Structure and functions of mitochondria and lysosomes

Mitochondria 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;

2) store hereditary material in the form of mitochondrial DNA.

Side functions - participation in the synthesis of steroid hormones, some amino acids (for example, glutamine).

Mitochondrial structure

Mitochondria have two membranes: outer (smooth) and inner (forming outgrowths - leaf-shaped (cristae) and tubular (tubules)).

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, ribosomes, a set of t-RNA, enzymes of reduplication, transcription, translation of hereditary information.

Mitochondria reproduce by ligation; mitochondria are characterized by relative autonomy within the cell.

Lysosomes 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. 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 subdivided 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 hydrolases and 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.

9. 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. Closely packed cisterns and channels of granular ER form a layered structure where protein synthesis is most active. 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 dictiosomes (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.

10. Structure and functions of non-membrane cell structures

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 mRNA strands. The complex of a group of ribosomes united by a single mRNA molecule like a string of beads is called a polysome.

Polysomes of granular ER form proteins that are excreted from the cell and used for the needs of the whole organism.

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, cilia.

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. Types of microfilaments:

1) actin. Contain contractile proteins (actin), provide cellular forms of movement;

2) intermediate (10 nm thick). Their bundles are found along the periphery of the cell under the plasma membrane and along the circumference of the nucleus. They perform a supporting (framework) role.

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 located mutually perpendicular.

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.

Inside the cell is the cytoplasm. It consists of a liquid part - hyaloplasm (matrix), organelles and cytoplasmic inclusions.

Hyaloplasm is the main substance of the cytoplasm. Hyaloplasm can be considered as a complex colloidal system capable of existing in two states: sol-like (liquid) and gel-like, which mutually transform one into another.

Hyaloplasmic functions:

1) the formation of the true internal environment of the cell;

2) maintaining a certain structure and shape of the cell;

3) ensuring intracellular movement of substances and structures;

4) ensuring adequate metabolism both within the cell itself and with the external environment.

Inclusions are relatively non-permanent components of the cytoplasm. Allocate:

1) reserve nutrients that are used by the cell itself during periods of insufficient intake of nutrients from outside;

2) products that are to be released from the cell;

3) ballast substances of some cells.

11. Viruses. structure and reproduction. bacteriophages

Viruses are precellular life forms that are obligate intracellular parasites, that is, they can exist and multiply only inside the host organism.

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.

In some viruses, a supercapsid shell, also built of protein, is located on top of the capsid. 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).

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 is created. 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.

Retrovirus providing reverse transcription: a single-stranded DNA molecule is built on the 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. The genetic material is located in the bacteriophage head, which is covered with a protein coat (capsid) on top. 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.

12. Gametes. Properties, structure and functions of the egg and sperm

Gametes ensure the transfer of hereditary information between generations of individuals. 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, 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 of organisms of this species.

The second difference is the unusual nuclear-cytoplasmic ratio. In oocytes, 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.

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 or exposure to a factor that induces parthenogenesis.

The egg is a large, immobile cell that has a supply of nutrients. The size of the female egg is 150-170 microns. The functions of nutrients are different. They are performed:

1) components needed for protein biosynthesis processes;

2) specific regulatory substances;

3) the yolk providing nutrition to the embryo in the embryonic period.

The egg has membranes that prevent more than one sperm from entering the egg.

The egg usually has a spherical or slightly elongated shape, surrounded on the outside by a shiny membrane, which is covered with a radiant crown, or a follicular membrane. It plays a protective role, nourishes the egg.

The egg cell is deprived of the apparatus of active movement. The ovum is characterized by plasma segregation.

A sperm cell is a male reproductive cell (gamete). He has the ability to move. The dimensions of the spermatozoon are microscopic: the length of this cell in humans is 50-70 microns.

The structure of the sperm

The 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 acrosome, which is a modified Golgi complex. Here, the formation of hyaluronidase, an enzyme that is able to break down the mucopolysaccharides of the egg membranes, takes place. 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 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).

13. 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 released into the external environment;

2) internal. The male secretes reproductive products into the female genital tract.

Fertilization consists of three successive stages: convergence of gametes, activation of the egg, fusion of gametes (syngamy), acrosomal reaction.

Convergence of gametes

It is due to a combination of factors that increase the likelihood of meeting gametes: sexual activity of males and females, excessive production of spermatozoa, large sizes of eggs, secretion of gametes by gametes (specific substances that contribute to the convergence and fusion of germ cells). The ovum secretes gynogamons, which determine the directed movement of spermatozoa towards it (chemotaxis), and the spermatozoa secrete androgamones.

The acrosomal reaction is the release of proteolytic enzymes 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, 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 is separated and resorbed.

The activation of the egg occurs as a result of its contact with the sperm. There is a cortical reaction that protects the egg from polyspermy.

In the egg, the metabolism changes. The activation of the egg is completed by the beginning of the translational stage of protein biosynthesis.

Fusion of gametes

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 transforms into a female pronucleus 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 (containing 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.

14. Reproduction. Asexual reproduction, its role and forms

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. The life of cells is much shorter than the life of the organism itself, therefore its existence is supported 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 fitness enhances the importance of stabilizing natural selection; provides fast reproduction rates; used in practical selection.

2. Forms of asexual reproduction

In unicellular organisms, the following forms of asexual reproduction are distinguished: division, endogony, schizogony and budding, sporulation.

Division is typical for 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.

It occurs in sporozoans (malarial plasmodium), etc. There is a multiple division of the nucleus without cytokinesis. 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.

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. 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).

15. Sexual reproduction. Its types, role. Atypical sexual reproduction

Sexual reproduction occurs mainly in higher organisms.

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.

Sexual reproduction is carried out through gametes - germ 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 - sex glands.

The process of formation of germ cells is called gametogenesis.

If male and female gametes are formed in the body of one individual, then it is called hermaphroditic.

Types of sexual reproduction

1. During conjugation, special germ cells (sexual individuals) are not formed. In this case, there are two nuclei - macro- and micronucleus. 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 nucleus. Ordinary micro- and macronuclei are formed, the cells disperse. In this process, there is no increase in the number of individuals, but there is an exchange of hereditary information.

2. 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.

Differences between gametes during evolution

Isogamy, when germ cells do not yet have differentiation. With further complication of the process, anisogamy occurs: male and female gametes differ, but quantitatively (in chlamydomonas). Finally, in the Volvox algae, the large gamete becomes immobile and the largest of all gametes.

Atypical sexual reproduction

Parthenogenesis - daughter organisms develop from unfertilized eggs.

Meaning of parthenogenesis:

1) reproduction is possible with rare contacts of heterosexual individuals;

2) the population size increases sharply;

3) occurs in populations with high mortality during one season.

Types of parthenogenesis:

1) obligate (mandatory) parthenogenesis;

2) cyclic (seasonal) parthenogenesis;

3) facultative (optional) parthenogenesis. There are also natural and artificial

parthenogenesis.

Gynogenesis. The sperm enters the egg and only stimulates its development. The nucleus of the sperm cell does not merge with the nucleus of the egg.

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.

16. Life cycle of a cell. Concept, meaning and phases

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.

Mitosis is the main type of somatic eukaryotic cell division. The division process includes several successive phases and is a cycle. Its duration varies and ranges from 10 to 50 hours in most cells.

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.

2. The mitotic cycle consists of four successive periods:

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. Mitochondria and chloroplasts divide. 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. 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;

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.

17. Mitosis. Characteristics of the main stages. Atypical forms of mitosis

Cell division includes two stages - nuclear division (mitosis, or karyokinesis) and cytoplasmic division (cytokinesis).

Mitosis consists of four successive phases.

Phases of mitosis:

1) prophase. The centrioles of the cell center divide and diverge to opposite poles of the cell. From microtubules, a spindle is formed, which connects the centrioles 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 envelope is divided into separate fragments. 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 attach 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 opposite poles of the cell. 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. The formation of a constriction in the equatorial plane begins, which deepens more and more and finally completely divides the mother cell into two daughter cells. Atypical forms of mitosis

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.

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.

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.

18. Meiosis, stages and meaning

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.

meiosis stages

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 - the 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 body phase 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.

The 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.

19. Gametogenesis. Concept, stages

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.

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. 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 ogonies occurs in the embryonic period.

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. Cells increase in size and turn into spermatocytes and oocytes of the first order. 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 . 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.

20. The concept of ontogenesis. Stages. Stages of embryonic development

Ontogenesis is the process of individual development of an individual from the moment a zygote is formed during sexual reproduction until the end of life.

Ontogeny is divided into three periods:

1. 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:

1) the embryonic (embryonic) period lasts from the moment of fertilization of the egg to the release of the embryo from the egg membranes;

2) the larval period occurs in some representatives of the lower vertebrates, the embryos of which, after emerging from the egg membranes, exist for some time, not having all the features of a mature individual;

3) 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;

4) juvenile period. During this period, the individual grows intensively, the final formation of the structure and function of organs and systems occurs.

2. In the reproductive period, an individual realizes its ability to reproduce. During this period of development, it is finally formed and resistant to the action of adverse external factors.

3. The post-reproductive period is associated with the progressive aging of the body. Stages of embryonic development

1. 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 the other.

2. 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) by immigration of individual cells, by epiboly (fouling), or by delamination (splitting into two plates). The outer germ layer is formed - ectoderm, and the inner - endoderm. Then comes the stage of histo- and organogenesis. At the same time, the rudiment of the nervous system, neyru-la, is first formed. 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.

21. G. Mendel's laws. Inheritance. Di- and polyhybrid crosses

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 by a small number of mutually exclusive options. 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.

Depending on the localization of the gene in the chromosome and the interaction of allelic genes, there are:

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's first law

The law of uniformity of hybrids of the first generation, or the law of dominance. In case of 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.

Hybridological analysis is the formulation of a system of crosses that makes it possible to identify patterns of inheritance of traits. Terms and conditions:

1) parent individuals must be of the same species and reproduce sexually;

2) parental individuals must be homozygous for the studied traits;

3) parental individuals must differ in the studied characteristics;

4) parental individuals are crossed with each other once to obtain hybrids of the first generation F1;

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.

Di- and polyhybrid crosses. 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.

Mendel's third law

Law of independent inheritance: splitting for each pair of traits proceeds independently of other pairs of traits.

Mendel's experiments formed the basis of a new science - genetics.

Genetics is the science that studies heredity and variation.

22. Interactions of allelic genes. Dominance, co-dominance. Interallelic complementation. Inheritance of blood groups of the ABO system

In the interaction of allelic genes, different variants of the manifestation of a trait are possible.

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 individual's genotype and heterozygotes (AA1) do not phenotypically differ from homozygotes for this allele (AA).

In the heterozygous genotype (AA1), the allele (A) is dominant. The presence of the allele (A1) 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 heterozygous rosygotes CC1. 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. Inheritance of blood groups of the ABO system Inheritance of blood groups of the ABO system in humans has some peculiarities. 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.

23. Non-allelic genes. Inheritance of sex-linked traits

Non-allelic genes are genes located in different parts of the chromosomes and encoding different proteins.

1. Complementary (additional) action of genes is a type of interaction of non-allelic genes, the dominant alleles of which, when combined in the genotype, cause 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.

2. 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 an epistatic gene does not have its own phenotypic manifestation, then it is called an inhibitor and is denoted by the letter I.

Epistatic interaction of non-allelic genes can be dominant and recessive.

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.

The sex of an organism is a set of signs and anatomical structures that provide sexual reproduction and the transmission of hereditary information.

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 are traits that are encoded by genes located on the sex chromosomes. In humans, traits encoded by X-chromosome genes can appear in both sexes, and those encoded by Y-chromosome genes - only in men.

There are X-linked and Y-linked (Holandric) 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 transmitted by the mother to all offspring. A man passes on his X-linked dominant trait only to his daughters.

Y-linked genes are present in the male genotype only and are passed down from generation to generation from father to son.

24. Variability. Concept, Types. Mutations

Variability is a property of living organisms to exist in various forms (options).

Types of variability

1. Hereditary (genotypic) variability is associated with a change in the genetic material itself.

2. 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 for the same trait varies from individual to individual. The scope of the reaction rate of various traits also varies. Modification variability in most cases is adaptive in nature, and most of the changes that occur in the body under the influence of certain environmental factors are beneficial. However, phenotypic changes sometimes lose their adaptive character.

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.

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.

2. Heteroploidy - a change in the number of individual chromosomes in the karyotype.

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.

25. 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. Full linkage of genes, i.e., joint inheritance, is possible in the absence of the process of crossing over. This is typical for genes of sex chromosomes that are heterogametic for sex chromosomes of organisms (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 cross-true 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, unit distance of 1% of crossing over.

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. 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. For the determination, chromosomes with a modified structure are used. A standard dihybrid crossover analysis is performed, in which one of the traits under study is encoded by a gene localized on a chromosome with an altered structure, and the second is encoded by a gene localized 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 the cards to formulate the main provisions of the chromosomal 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.

26. Methods for studying human heredity

1. 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 of urban dwellers and compiling a legend about each of them; it is necessary to collect information about relatives in three to 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:

a) definition of a group of diseases;

b) determination of the type and variant of inheritance;

c) determination of the probability of manifestation of the disease in the proband.

2. 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) method for determining X-chromatin of interphase chromosomes;

2) method for determining Y-chromatin of interphase chromosomes;

3) metaphase chromosomes to determine the number and group membership of chromosomes;

4) metaphase chromosomes for identification of all chromosomes according to the features of transverse striation.

3. Biochemical methods - they are mainly used in the differential diagnosis of hereditary metabolic disorders with a known defect in the primary biochemical product of a given gene, divided into qualitative, quantitative and semi-quantitative. Blood, urine or amniotic fluid is examined.

Qualitative methods are simpler and are used for mass screening.

Quantitative methods are more accurate, but also more laborious; they are used only for special indications.

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.

4. DNA diagnostics is the most accurate method for diagnosing monogenic hereditary diseases.

The 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.

5 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.

27. Biosphere. Definition. Components, the noosphere and its problems

The doctrine of the biosphere was developed by 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 is a layer with a thickness of 2-3 to 10 km (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.

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;

2) nekton - actively moving in the water column;

3) benthos - organisms that live at the bottom of water bodies. 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.

28. Ways of parasitism. Classification

Parasitism is a phenomenon 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 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 to endoparasitism in the case of commensals using not only waste, part of the diet, and even its tissues.

3. Primary endoparasitism as a result of the 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 host organism and the external environment.

2. The parasite has a smaller body size and a shorter life span compared to the host.

3. 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 - their specific feature.

Classification of parasites

Depending on the time spent on the host, parasites can be permanent.

According to the mandatory parasitic way of life, parasites are obligate, leading a parasitic way of life, and facultative, leading a non-parasitic way of life.

According to the habitat, parasites are divided into ectoparasites, intradermal parasites, cavity parasites, and endoparasites.

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. A complex life cycle is characteristic of parasites that have at least one intermediate host.

One and the same host species can be a food habitat for several species of parasites.

Parasites change hosts. Many parasites have multiple hosts. The final (definitive) host is the species in which the parasite is in its adult state and reproduces sexually and intermediates asexually.

A reservoir host is a host in whose body the parasite remains viable and accumulates.

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.

29. Review of the simplest. Their structure and activity

Protozoa are unicellular organisms whose body consists of 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.

One cell can do everything: to eat, and move, and attack, and escape from enemies, and survive adverse environmental conditions, and multiply, and get rid of metabolic products, and protect itself from drying out and from excessive penetration of water into the cell.

The sizes of the simplest are from 3-150 microns to 2-3 cm in diameter.

About 100 species of protozoa are known. Their habitat is water, soil, host organism (for parasitic forms).

The simplest have organelles of general (mitochondria, ribosomes, cell center, ER, etc.) and special purpose. Organs of movement: pseudopods, flagella, cilia, digestive and contractile vacuoles.

Most protozoa have one nucleus, but there are representatives with several nuclei. The nuclei 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 covers are represented either by a cytoplasmic membrane (in an amoeba) or a pellicle (in an euglena).

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 or through any place in the cell. Through contractile vacuoles, osmotic regulation is carried out, metabolic products are removed.

Respiration occurs across the entire surface of the cell.

Irritability is represented by taxis.

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. Cells exchange genetic information, but there is no increase in the number of individuals.

The simplest are able to exist in two forms - trophozoite (a vegetative form capable of active nutrition and movement) and a cyst, which is formed under adverse conditions. When exposed to favorable living conditions, excystation occurs, the cell begins to function in a trophozoite state.

Many representatives of the Protozoa phylum are characterized by the presence of a life cycle.

The generation time for protozoa is 6-24 hours.

Diseases caused by protozoa are called protozoan.

30. General characteristics of the sarcode class (rhizomes). Free-living and parasitic amoeba. Prevention

Representatives of this class are the most primitive of the simplest. They are able to form pseudopodia (pseudopodia), which serve to capture food and movement. Therefore, they do not have a permanent body shape, their outer cover is a thin plasma membrane.

free-living amoeba

Over 100 sarcodes are known. Representatives of the amoeba order (Amoebina) are of medical importance.

Freshwater amoeba (Amoeba proteus) lives in fresh water, puddles, small ponds. 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.

1. Dysentery amoeba (Entamoeba histolytica) - 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, asymptomatic carriage of amoeba cysts is possible.

This form of the disease is also subject to mandatory treatment, since carriers are dangerous to others.

2. 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, it does not secrete proteolytic enzymes on erythrocytes and does not penetrate the intestinal wall. Forms cysts.

3. Mouth amoeba (Entamoeba gingivalis) - lives in carious teeth, plaque, on the gums and in the crypts of the palatine tonsils in more than 25% of healthy people. 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.

31. Pathogenic amoeba. Structure, forms, life cycle

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. 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. Can penetrate quite deeply into 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, 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 parasite carriers, the disease in which is asymptomatic.

Life cycle of the parasite. By swallowing cysts from contaminated water or food. In the lumen of the colon, 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.

32. Class Flagellates. Structure and life

Class Flagellates (Flagellata) has about 6000-8000 representatives. They have a constant 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 between the flagellum and the pellicle there passes a wavy cytoplasmic membrane - 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 axo-style, which passes through the entire cell in the form of a dense strand.

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. The breathing of euglena is the same as that of wameba. 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.

33. Trichomonas. Species, morphological characteristics. Diagnostics. Prevention

Trichomonas (flagellate class) are the causative agents of diseases called trichomoniasis.

Urogenital trichomonas (Trichomonas vagi-nalis) 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.

34. Giardia. Morphology. Vital activity of Leishmania. Forms. Diagnostics. Prevention

Giardia belong to the class Flagella. Causes a disease called intestinal giardiasis. Younger children are more commonly affected.

It lives in the small intestine, mainly in the duodenum, can penetrate into the bile ducts (intra- and extrahepatic), and from there - into the gallbladder and liver tissue. Giardiasis is ubiquitous.

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. In the expanded part there is a suction disk. Along the body are 2 thin axostyles.

Giardia are capable of forming cysts. Mature cysts are oval in shape, contain 4 nuclei and several supporting axostyles. In the external environment, they remain viable for several weeks.

Infection occurs by ingestion of cysts that have been ingested in food or drinking water.

Vegetative forms (trophozoites) are formed in the small intestine.

Giardia use nutrients that they capture from the surface of intestinal epithelial cells using pinocytosis.

The processes of parietal digestion and absorption of food are disturbed, as well as inflammation of the intestines and gallbladder.

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. Detection of cysts in feces, trophozoites in the contents of the duodenum obtained by fractional duodenal sounding.

Prevention.

1. Personal.

2. Public.

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.

They exist in two forms: flagellated (leptomonadal, otherwise promastigote) and non-flagellated (leishmanial, otherwise amastigote).

Diagnosis in skin and mucous form. Discharge is taken from a skin or mucous ulcer and smears are prepared for subsequent microscopy.

In the visceral form, a punctate of the red bone marrow is obtained (with a puncture of the sternum) or lymph nodes, followed by the preparation of a smear or imprint for microscopy, sowing the material 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).

35. Trypanosomes (Tripanosoma). Kinds. Life cycle. Diagnostics. Prevention

The causative agents of trypanosomiasis are trypanosomes (flagellate class). African trypanosomiasis causes Trypanosoma bruceigambiensi and T. b. rhodesien-se. 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.

It lives in blood plasma, lymph, lymph nodes, cerebrospinal fluid, the substance of the brain and spinal cord, serous fluids.

The disease is ubiquitous throughout Africa.

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 tsetse flies Glossina palpalis (lives near human habitation), T. b. rhodes-iense, 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 human, trypanosomes enter its stomach, where they multiply and go through several stages. A full development cycle takes 20 days. Flies whose saliva contains trypanosomes in an invasive (metacyclic) 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.

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. In their body, tri-panosomes multiply. After the bite, the bugs defecate, the pathogen in the invasive stage enters the wound with feces. 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. Vector control, prophylactic treatment of healthy people in the foci of trypanosomiasis, making the body immune to the pathogen.

36. 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.

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. Gametes merge to form a zygote, which turns into a cyst, sporogony occurs in it - 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. Thus, these are zoonotic and anthropozoonotic diseases, the prevention of which is a difficult task. These diseases can be transmitted non-transmissively (like Toxoplasma), that is, they do not have a specific carrier, or transmissively (like malarial plasmodia), that is, through carriers.

Diagnosis is rather complicated, 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 gondii is the causative agent of toxoplasmosis. Man is the 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.

37. Toxoplasmosis: causative agent, characteristics, development cycle, prevention

The causative agent of toxoplasmosis is toxoplasma (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.

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. Then 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-we 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, during medical manipulations - transfusion of donor 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, 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.

38. Malarial plasmodium: morphology, development cycle. Diagnostics. Prevention

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.

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, where tissue schizogony occurs. It corresponds to the incubation period of the disease. 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. The food of the parasite is globin, and the remaining free heme is the strongest poison. It is his entry into the blood that causes terrible attacks of malarial fever. Body temperature rises high.

In humans, Plasmodium reproduces only asexually - schizogony. Man is an intermediate host. The sexual process takes place in the body of the mosquito. The mosquito is the definitive host and also the carrier.

Malaria is a severe disease characterized by periodic debilitating attacks of fever with chills and profuse sweating. When a large number of merozoites leave the erythrocytes, many toxic waste products of the parasite itself and the decay products of hemoglobin, which feed on plasmodium, are released into the blood plasma. When exposed to them, a pronounced intoxication occurs, which manifests itself in a sharp paroxysmal increase in body temperature, the appearance of chills, headaches and muscle pain, and severe weakness. These attacks occur acutely and last an average of 1,5-2 hours.

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 malaria patients and extermination of mosquitoes.

When traveling to areas unfavorable for malaria, you should take prophylactic antimalarial drugs, protect yourself from mosquito bites.

39. Overview of the structure of ciliates. Balantidia. Structure. Diagnostics. Prevention

Ciliates are the most complex protozoa. They have numerous organelles of movement - cilia, which completely cover the entire body of the animal. 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.

Each individual has at least two nuclei - large (macronucleus) and small (micronucleus). The large nucleus is responsible for metabolism, and the small nucleus regulates the exchange of genetic information during the sexual process (conjugation). 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. 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. On the ventral side of the ciliate there is a cellular mouth (cytostome), which passes into the pharynx (cytopharyngs). The pharynx opens directly into the endoplasmic digestive vacuole.

The undigested residue is thrown out through the powder, the representative is the infusoria shoe, which lives in small reservoirs, puddles.

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.

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 and can invade the wall of the colon, causing the formation of bleeding and suppurating ulcers. Sometimes perforation of the intestinal wall occurs. Balantidia can penetrate into the bloodstream from the intestinal wall and spread 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. Cysts and trophozoites of balantidia are found in the smear. Mucus, blood, pus and a lot of parasites are revealed.

Prevention.

1. Personal. Compliance with the rules of personal hygiene.

2. Public. Sanitation of public places, monitoring of public water sources, rodent control, hygienic keeping of pigs.

40. Type flatworms. characteristic features of the organization. General characteristics of the class flukes

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. The main aromorphoses of flatworms:

1) bilateral symmetry of the body;

2) development of the mesoderm;

3) the emergence of organ systems.

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 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. Leftover food is expelled through the mouth.

The excretory system is represented by protone-fridia.

Flatworms combine the characteristics of both sexes - male and female.

Representatives of two classes are of medical importance - Flukes (Trematodes) and Tapeworms (Cestoidea).

Flukes class. general characteristics

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; there is another sucker on the ventral side. Additional organs of attachment in some species are small spines that cover the entire body.

Flukes are hermaphrodites. Male reproductive system: a pair of testes, two vas deferens, ejaculatory canal, copulatory organ (cirrus). Female reproductive system: ovary, oviducts, vitelline glands, seminal receptacle, uterus, genital cloaca.

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. 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.

When it reproduces, multicellular redia are formed, which can generate in cercariae. Their further development proceeds in the body of the final or second intermediate host.

In the organism of the final host, the invasive stages of flukes migrate in it and find the organ necessary for further development.

Migration is accompanied by severe intoxication and allergic manifestations.

Diseases caused by flukes are collectively called trematodes.

41. Liver and feline flukes

The liver fluke, or fasciola (Fasciola hepatica), is the causative agent of fascioliasis.

The disease is ubiquitous.

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.

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.

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).

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. From the liver tissue, the parasite can penetrate into the bile ducts and cause blockage, jaundice appears.

Diagnostics. Detection of fasciola eggs in the faeces of a patient.

Prevention. Thoroughly wash vegetables and herbs, do not use unfiltered water for drinking. Identify and treat sick animals, sanitize pastures.

The feline, or Siberian, fluke (Opisthorchis felineus) is the causative agent of opisthorchiasis.

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 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 enter the water and, actively swimming in it, penetrate into the body of the fish or are swallowed by it. 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.

Diagnostics. 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.

42. Schistosomes

Schistosomes are the causative agents of schistosomiasis. All parasites live in blood vessels, mainly in veins. These are seperate organisms. The body of males is shorter and wider. Females have a cord-like shape, when they reach puberty, they are connected in pairs. After that, the female lives in the gynecophoric canal on the ventral side of the male.

Eggs are secreted from the vascular bed 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.

For some species of schistosomes, only humans are the definitive host, for others, various mammalian species. Intermediate hosts are freshwater molluscs. In their body, the development of larval stages occurs, and two generations of sporocysts are formed. The last generation forms cercariae, which are the invasive stage for the definitive host.

When penetrating through the skin, cercariae cause a specific lesion in the form of cercariasis - the appearance of a rash, itching, and allergic conditions.

Diagnostics. Detection in the urine or feces of a patient of eggs of schistosomes.

Statement of skin allergological tests, immunological diagnostic methods are used.

Prevention. Use only disinfected water for drinking. Fight against an intermediate host - aquatic molluscs. Protection of water bodies from pollution. Three main types of blood flukes parasitize in the human body.

1. Schistosoma heamatobium - the causative agent of urogenital schistosomiasis, lives in the large veins of the abdominal cavity and organs of the genitourinary system.

The final host is man and monkeys.

Intermediate hosts are various aquatic mollusks.

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.

Diagnostics. Detection of parasite eggs by microscopy of urine.

2. Schistosoma mansoni - the causative agent of intestinal schistosomiasis.

It parasitizes in the veins of the mesentery and large intestine. It also affects the portal system of the liver.

The final hosts of the parasite are humans, monkeys, dogs, and rodents. Intermediate hosts are aquatic mollusks.

Pathological changes occur in the large intestine (colitis, bloody diarrhea) and liver (blood stasis occurs, cancer is possible).

Diagnostics. Detection of eggs in the faeces of the patient.

3. Schistosoma japonicum - 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.

The final hosts are humans, many domestic and wild mammals. Intermediate hosts are aquatic mollusks.

Manifestations as in intestinal schistosomiasis.

Diagnostics. Detection of eggs in the faeces of a patient.

43. General characteristics of the class Tapeworms. Bull tapeworm

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 a tapeworm is tape-shaped. Consists of separate segments - pro-glottids. At the anterior end of the body is the head (scolex), then the non-segmented neck. Attachment organs are located on the head - suckers, hooks, suction slots (bothria).

Two stages of development - sexually mature (live in the body of the final host) and larval (parasite in the intermediate host) in the uterus inside the shells of the egg, a six-hooked embryo is formed - the oncosphere. 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. 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.

Diseases caused by tapeworms are called cestodosis.

Bull tapeworm (Taeniarhynchus saginatus) is the causative agent of teniarhynchosis. There are only 4 suction cups on the head.

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.

Able 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 the 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.

Diagnostics. Detection in the faeces of the patient mature segments.

Prevention.

1. Personal. Thorough heat treatment of meat.

2. Public. Strict supervision of the processing and sale of meat. Carrying out sanitary and educational work with the population.

44. Dwarf pork tapeworm

Pork, or armed, tapeworm (Taenia solium) - the causative agent of teniasis. The final owner is only a human. Intermediate hosts - a pig, occasionally a man. The segments are excreted with human feces 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.

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.

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.

Treatment of cysticercosis is only surgical.

Diagnostics. Detection in the faeces of the patient mature segments.

Prevention.

1. Personal. Thoroughly cooked pork.

2. Public. Pasture protection Strict supervision of the processing and sale of meat.

Dwarf tapeworm (Hymenolepis nana) is the causative agent of hymeno-lepidosis. The head is pear-shaped, has 4 suckers and a proboscis with a halo of hooks. Strobila contains 200 or more segments, only eggs enter the environment. The size of the eggs is up to 40 microns. They are colorless and have a rounded shape.

Man is both an intermediate and a final host. Oncospheres are introduced into the villi of the small intestine, where cysticercoids develop from them. Juveniles attach to the intestinal mucosa and reach sexual maturity.

pathogenic action. The processes of parietal digestion are disturbed. The body is poisoned by the waste products of the helminth. Intestinal activity is disturbed, abdominal pain, diarrhea, headaches, irritability, weakness, fatigue appear.

The human body is able to develop immunity against the parasite. 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. Compliance with the rules of personal hygiene.

2. Public. Thorough cleaning of children's institutions.

45. Echinococcus and broad tapeworm. Diphyllobothriasis

Echinococcus (Echinococcus granulosus) is the causative agent of echinococcosis.

The sexually mature form of the parasite is 2-6 mm long and consists of 3-4 segments. On the head (scolex) there are 4 suckers and a proboscis with two rims of hooks.

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 feces of the definitive hosts contain parasite eggs; mature echinococcus segments can actively crawl out of the anus and spread through the animal's fur, leaving eggs on it.

Humans and other intermediate hosts become infected by ingesting the eggs. 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 the larval stage, echinococcus is located in the liver, brain, lungs, tubular bones. Finna can squeeze organs, causing them to atrophy. The echinococcal bladder contains liquid with parasite dissimilation products; if it enters the bloodstream, toxic shock may occur. 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, examination and treatment of domestic and service animals. Destruction of the corpses of sick animals.

Wide tapeworm (Diphyllobotrium latum) - the causative agent of diphyllobothriasis. It is attached to the intestinal wall with the help of two bothria, or suction slits, which look like grooves.

Eggs enter the water with human feces, they produce coracidia, which are swallowed by crustaceans (the first intermediate host), in the intestines of which they lose cilia and turn into a larva - a procercoid. The crustacean is swallowed by a fish (the second intermediate host), in its muscles the procercoid passes into the next (larval) stage - the plero-cercoid.

A person becomes infected by eating raw or half-cooked fish or freshly salted caviar.

Diphyllobothriasis - a dangerous disease occurs intestinal obstruction. The parasite consumes nutrients from the intestines. Intoxication dysbacteriosis, B12 deficiency anemia of folic acid.

Diagnostics. Detection of eggs and fragments of mature segments of the broad tapeworm in faeces.

Prevention.

1. Personal. Refusal to eat raw fish.

2. Public. Protection of water bodies from fecal pollution.

46. Roundworms. Structural features. Ascaris human. Life cycle. Diagnostics. Prevention

More than 500 species of roundworms have been described. They live in different environments. The main aromorphoses of the type:

1) primary body cavity;

2) the presence of the posterior intestine and anus;

3) dichotomy.

The body is unsegmented, has a rounded shape. The body is three-layered, develops from endo-, meso- and ectoderm. There is a skin-muscular sac. It consists of an outer inextensible dense cuticle, hypodermis and one layer of longitudinal smooth muscle fibers. In the hypodermis, metabolic processes are actively taking place.

Roundworms have a primary body cavity - a pseudocoel. It contains all the internal organs. They form five differentiated systems - digestive, excretory, nervous, sexual and muscular.

The digestive system is represented by a through tube.

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 excretory system is built according to the type of proto-nephridia. 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.

Ascaris human (Ascaris lumbricoides) is the causative agent of ascariasis.

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.

A person becomes infected with ascaris through unwashed vegetables and fruits, on which the eggs are located. The larva emerges from the egg in the intestine. 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. Headache, weakness, drowsiness, irritability develop, memory and working capacity decrease. There may be mechanical intestinal obstruction, appendicitis, blockage of the bile ducts, abscesses may form in the liver.

Diagnostics. Detection of human roundworm eggs in the patient's feces.

Prevention.

1. Personal.

2. Public. Sanitary and educational work.

47. Pinworm and Whipworm

Pinworm (Enterobius vermicularis) is the causative agent of enterobiasis.

The pinworm is a small white worm. 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.

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.

From the hands they are brought into the mouth by the patient himself (autoreinvasion occurs).

There is poor sleep, lack of sleep, irritability, deterioration of health, possibly the development of appendicitis, inflammation and violation of the integrity of the intestinal wall.

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.

Prevention.

1. Personal. Careful observance of the rules of personal hygiene.

2. Public. Regular examination of children. Human whipworm (Trichocephalus trichiurus) is the causative agent of trichuriasis. The causative agent is localized in the lower parts of the small intestine (mainly in the caecum), the upper parts of the large intestine.

Vlasoglav parasitizes only in the human body. There is no change of owners. This is a typical geohelminth that develops without migration. 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. 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.

The parasite feeds on human blood. 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 disturbed, abdominal pain occurs, there may be convulsions, anemia (anemia) may 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. Compliance with the rules of personal hygiene.

2. Sanitary and educational work with the population.

48. Trichinella and hookworm

Trichinella (Trichinella spiralis) is the causative agent of trichinosis.

Trichinella larvae live in the striated muscles, and sexually mature individuals live in the small intestine.

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.

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: the diaphragm, intercostal, chewing, deltoid, gastrocnemius, encapsulate in the muscles and can live for several decades.

Clinical manifestations of the disease vary from asymptomatic to fatal. The incubation period is 5-45 days.

Diagnostics. Anamnestically. Muscle biopsy study. Immunological reactions are applied.

Prevention. Thermal processing of meat.

hookworm

Crooked head of the duodenum (Ancylostoma duodenale) is the causative agent of ankylostomiasis. The life expectancy of the parasite is 4-5 years.

It parasitizes only in humans. Fertilized eggs with faeces enter the environment, where, under favorable conditions, larvae, called rhabditis, emerge from them in a day. They can enter the human body through the mouth. But more often they are introduced through the skin.

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.

Parasites secrete anticoagulant substances that prevent blood from clotting, so intestinal bleeding can occur.

There is intoxication of the organism with the products of the vital activity of the parasite, the development of massive intestinal bleeding (anemia), and allergies to the parasite. There are pains in the abdomen, indigestion, headaches, weakness, fatigue.

Diagnostics. Detection of larvae and eggs in the patient's feces.

Prevention.

1. Personal.

2. Public.

49. Rishta. Biohelminths

Rishta (Dragunculus medinensis) - the causative agent of dragunkulosis.

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. 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. 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 micro-filariae. 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.

If the parasite is located next to the joint, its mobility is impaired. There are painful ulcers and abscesses on the skin. The parasite also has a general toxic and allergic effect.

Diagnostics. Visual detection of sexually mature forms, which look like convoluted, clearly visible ridges under the skin.

Prevention.

1. Personal. You should not drink unfiltered and unboiled water from open reservoirs in the foci of the disease.

2. Public. Protection of water supply sites.

Biohelminths are parasites that develop with the participation of intermediate hosts and cause similar diseases - filariasis.

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.

The main types of filariae are human parasites.

1. Wuchereria banctofti. Parasites are localized in the lymph nodes and blood vessels, causing stagnation of blood and lymph, elephantiasis, and allergization appear.

2. Brugia malayi.

3. Oncocerca volvulus. In the body, parasites are localized under the skin of the chest, head, limbs, causing the formation of painful nodules.

4 Loa loa. In the body: under the skin and mucous membranes, where painful nodules and abscesses occur.

5. Mansonella. In the body of which the parasite is localized in adipose tissue, under the serous membranes, in the mesentery of the intestine.

6. Acantocheilonema.

Diagnostics. Detection of microfilariae in the blood. Prevention. Carrier control. Early detection and treatment of patients.

50. Type Arthropods. Diversity and morphology

More than 1 million species belong to Arthropoda arthropods. Representatives of the classes Arachnids and Insects are of the greatest medical importance, the study of the pathogenic action of which is carried out by the section of medical parasitology - arachnoentomology. 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.

Aromorphoses of the Arthropod type:

1) external skeleton;

2) jointed limbs;

3) striated muscles;

4) isolation and specialization of muscles.

The phylum Arthropoda includes the subtypes Gill-breathers (the class Crustacea is of medical importance), Cheliceridae (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-layered body, i.e., development from three germ layers. There is bilateral symmetry and heteronomous articulation of the body. 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. There is an outer chitinous cover, which performs a protective role.

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.

excretory system. It is represented by modified metanephridia 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.

The nervous system is built from the head ganglion, near-pharyngeal commissures and the ventral nerve cord from partially fused nerve ganglions. The sense organs are well developed - smell, touch, taste, sight, hearing, balance organs.

There are endocrine glands that 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.

51. Ticks. Scabies pruritus and acne gland

They belong to the subtype Cheliceraceae, class Arachnids. They have an unsegmented body of an oval or spherical shape, covered with a 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 are used for movement.

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 trachea.

The circulatory system consists 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.

The mature female lays eggs, which hatch into larvae. After the first molt, the larva turns into a nymph. After the last molt, the nymph turns into an imago.

A small part of the species has adapted to constant parasitism on humans. These include scabies and acne gland, which lives in the sebaceous glands and follicles of the skin.

Scabies itch (Sarcoptes scabiei) is the causative agent of human scabies (scabies). Refers to permanent human parasites, in the body of which it lives in the stratum corneum of the epidermis. On a person, scabies of dogs, cats, horses, pigs, sheep, goats, etc. can parasitize. They do not live long, but cause characteristic changes on the skin.

The oral apparatus is adapted to gnaw through passages in human skin, where the female lays her eggs. This is where the metamorphosis takes place. 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.

Diagnostics. On the skin, straight or twisted strips of an off-white color are found.

Prevention. Compliance with the rules of personal hygiene. Sanitary supervision of hostels, public baths, etc.

Acne gland (Demodex folliculorum) - the causative agent of demodicosis. 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. 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.

52. Family Ixodid ticks. Dog taiga and other ticks

All ixodid ticks are temporary bloodsuckers. The temporary host on which they feed is called the host-feeder. The integuments of the body and the digestive system of the female are highly extensible. This allows them to eat rarely, 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 with sharp, backward-directed teeth. 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. Ixodid ticks are highly fertile.

Most often, a tick changes three hosts during development, on each of which it feeds only once.

Many ixodid ticks are carriers of pathogens of dangerous diseases in humans and animals. Among these diseases, tick-borne spring-summer encephalitis is the most famous.

Dog tick.

Supports the existence in nature of foci of tularemia among rodents, from which the disease is transmitted to humans and domestic animals.

The dog tick parasitizes many wild and domestic animals, humans; sticks to the owner for several days. It is a carrier of the causative agent of tularemia, 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.

The taiga tick 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.

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, goat birds.

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 Dermatocenter live in 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. Derma-tocenter 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).

53. Class Insects. Morphology, physiology, systematics. Squad Vshi. Kinds. Prevention

The class Insects 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. There are sensory organs on the head - antennae and eyes, 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 limbs lying near the mouth opening bear tactile bristles and serve to grasp and grind food. The abdomen has no limbs; most insects have two pairs of wings on the chest.

The musculature of insects is well developed and consists of striated muscle fibers. The CNS consists of the head ganglion, the parapharyngeal nerve ring, and the ventral nerve cord. The respiratory organs of insects are the trachea. The digestive organs consist of the anterior, middle and hindgut. The excretory organs are represented by malpighian vessels opening into the intestine. The circulatory system is not closed. Insects have a heart on the dorsal side, consisting of several chambers equipped with valves. The development of insects occurs with metamorphosis.

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. Squad Lice

The pubic louse lives on the pubis, in the armpits, less often on the eyebrows, eyelashes, and in the beard.

Common features for all types of lice are small size, a simplified development cycle, limbs adapted for fixation on the skin, hair and clothing of a person, a piercing-sucking mouth apparatus; wings are missing.

Head and body lice feed on human blood 2-3 times a day, and pubic lice feed 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. 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 diseases. Head and body lice are specific carriers of pathogens of relapsing and epidemic typhus, Volyn fever.

Prevention. Compliance with the rules of personal hygiene.

For treatment, external and internal means are used: ointments and shampoos containing insecticides, as well as drugs taken orally.

54. Detachment of the Flea. Features of the developmental biology of mosquitoes

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. The hind legs of fleas are elongated, jumping. The tarsi of all legs are five-membered, 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.

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 worm-like larva emerges from the egg; an adult flea emerges from the pupa with organic remains. The most famous representatives are the rat flea and the human flea.

Fleas bite humans at night. Toxic substances in their saliva cause intense itching.

Fleas are carriers of plague pathogens. Rats, ground squirrels, ferrets, etc. serve as natural reservoirs of plague. Rodents are also sources of other infections: tularemia, rat typhus.

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 carriers of over 50 diseases. Mosquitoes - representatives of the genera Culex and Aedes (non-malarial) are carriers of pathogens of Japanese encephalitis, yellow fever, anthrax, representatives of the genus Anopheles (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.

The malarial mosquito is the definitive host, while humans are the intermediate host of the protozoan malarial plasmodium (a type of sporozoan). Development cycle of malarial plasmodium:

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 the gametocytes of 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.

55. 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.

Humans have 3 habitats:

1) natural;

2) social;

3) technogenic.

A person is an object of various environmental factors (sunlight, other creatures), on the other hand, a person himself is an ecological (anthropogenic) factor.

The environment is a set of factors and elements that affect the organism in its habitat.

Biological factors, or driving forces of evolution. These include hereditary variability and natural selection.

The adaptation of organisms to the effects of environmental factors is called adaptation.

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.

The main sources of air pollution are cars and industrial enterprises causing the greenhouse effect.

The main cause of pollution of the hydrosphere is the discharge of untreated wastewater from industrial and municipal enterprises, as well as agricultural land.

Lithosphere - a fertile layer of soil 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.

An ecological crisis is a violation of relationships within an ecosystem or irreversible phenomena in the biosphere caused by human activities.

56. Poisonous animals. Arachnids. Vertebrates

The class Arachnida includes spiders, scorpions, phalanges, ticks.

Poisonous arachnids feed on live prey. By piercing the insect's chitinous integuments with their chelicerae, the spiders inject the poison into the inside along with the digestive juices.

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.

On the jointed flexible metasome (tail) there is an anal lobe ending in a poisonous needle. In the anal lobe there are two poisonous glands, the ducts of which open near the top of the needle.

Squad Spiders

The front pair of limbs of chelicera spiders is designed to protect and kill prey. The chelicerae are in front of the mouth. The considered representatives of the group of poisonous spiders are characterized by a 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, at the end of which the ducts of two poisonous glands open.

Poisonous Vertebrates

They contain substances in the body 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 various organs and tissues. 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.

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 (stingray). An injection in the chest or abdomen can be fatal.

Poisonous snakes are characterized by the presence of poisonous teeth and glands that produce poison.

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. Where does the glandular duct open?

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.

Authors: Kurbatova N.S., Kozlova E.A.

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