Topic 10. BLOOD AND LYMPH

Characteristics and composition of blood

Blood is a tissue or one of the types of connective tissues.

The blood system includes the following components:

1) blood and lymph;

2) organs of hematopoiesis and immunopoiesis;

3) blood cells that have moved out of the blood into the connective and epithelial tissues and are able to return (recycle) back into the bloodstream (lymphocytes).

Blood, lymph and loose unformed connective tissue make up the internal environment of the body.

Blood functions:

1) transport. This function of the blood is extremely diverse. Blood carries out the transfer of gases (due to the ability of hemoglobin to bind oxygen and carbon dioxide), various nutrients and biologically active substances;

2) trophic. Nutrients enter the body with food, then are broken down in the gastrointestinal tract to proteins, fats and carbohydrates, absorbed and carried by the blood to various organs and tissues;

3) respiratory. Carried out in the form of transport of oxygen and carbon dioxide. Hemoglobin oxygenated in the lungs (oxyhemoglobin) is delivered by blood through the arteries to all organs and tissues where gas exchange (tissue respiration) occurs, oxygen is consumed for aerobic processes, and carbon dioxide is bound by blood hemoglobin (carboxyhemoglobin) and is delivered to the lungs through the venous blood flow, where it again occurs oxygenation;

4) protective. There are cells and systems in the blood that provide non-specific (complement system, phagocytes, NK cells) and specific (T- and B-systems of immunity) protection;

5) excretory. The blood removes the decay products of macromolecules (urea and creatinine are excreted by the kidneys with urine).

Together, these functions provide homeostasis (the constancy of the internal environment of the body).

Components of blood:

1) cells (shaped elements);

2) liquid intercellular substance (blood plasma).

The ratio of blood parts: plasma - 55 - 60%, formed elements - 40 - 45%.

Blood plasma consists of:

1) water (90 - 93%);

2) substances contained in it (7 - 10%).

Plasma contains proteins, amino acids, nucleotides, glucose, minerals, metabolic products.

Plasma proteins:

1) albumins;

2) globulins (including immunoglobulins);

3) fibrinogen;

4) enzyme proteins, etc.

The function of plasma is the transport of soluble substances.

Due to the fact that the blood contains both true cells (leukocytes) and post-cellular formations (erythrocytes and platelets), in the aggregate it is customary to refer to them collectively as formed elements.

Qualitative and quantitative composition of blood (blood test) - hemogram and leukocyte formula.

Hemogram of an adult:

1) erythrocytes contain:

a) for men - 3,9 - 5,5 x 10¹² in 1 l, or 3,9 - 5,5 million in 1 μl, hemoglobin concentration 130 - 160 g/l;

b) in women - 3,7 - 4,9 x 10¹², hemoglobin - 120 - 150 g / l;

2) platelets - 200 - 300 x 10⁹ in 1 l;

3) leukocytes - 3,8 - 9 x 10⁹ in 1 l.

Structural and functional characteristics of blood cells

Erythrocytes are the predominant population of blood cells. Morphological features:

1) do not contain a nucleus;

2) do not contain most organelles;

3) the cytoplasm is filled with pigment inclusions (hemoglobin).

Form of erythrocytes:

1) biconcave discs - discocytes (80%);

2) the remaining 20% ​​- spherocytes, planocytes, echinocytes, saddle-shaped, bifocal.

The following types of red blood cells can be distinguished by size:

1) normocytes (7,1 - 7,9 microns, concentration of normocytes in peripheral blood - 75%);

2) macrocytes (more than 8 microns in size, the number is 12,5%);

3) microcytes (less than 6 microns in size - 12,5%).

There are two forms of erythrocyte hemoglobin:

1) HbA;

2) HbF.

In an adult, HbA is 98%, HbF is 2%. In newborns, HbA is 20%, HbF is 80%. The life span of erythrocytes is 120 days. Old erythrocytes are destroyed by macrophages, mainly in the spleen, and the iron released from them is used by maturing erythrocytes.

In the peripheral blood, there are immature forms of erythrocytes called reticulocytes (1 - 5% of the total number of erythrocytes).

Red blood cell functions:

1) respiratory (transport of gases: O² and CO²);

2) transport of other substances adsorbed on the surface of the cytolemma (hormones, immunoglobulins, drugs, toxins, etc.).

Platelets (or platelets) are fragments of the cytoplasm of special cells of the red bone marrow (megakaryocytes).

Components of a platelet:

1) hyalomere (the base of the plate, surrounded by the plasmalemma);

2) granulomere (granularity represented by specific granules, as well as fragments of granular EPS, ribosomes, mitochondria, etc.).

Shape - rounded, oval, process.

According to the degree of maturity, platelets are divided into:

1) young;

2) mature;

3) old;

4) degenerative;

5) gigantic.

Life expectancy - 5 - 8 days.

Platelet function - participation in the mechanisms of blood coagulation through:

1) bonding of plates and formation of a blood clot;

2) the destruction of the plates and the release of one of the many factors that contribute to the transformation of globular fibrinogen into filamentous fibrin.

Leukocytes (or white blood cells) are nuclear blood cells that perform a protective function. They are contained in the blood from several hours to several days, and then leave the bloodstream and show their functions mainly in the tissues.

Leukocytes represent a heterogeneous group and are divided into several populations.

Leukocyte formula

Leukocyte formula - the percentage of various forms of leukocytes (to the total number of leukocytes equal to 100%).

Morphological and functional characteristics of granular leukocytes

Neutrophilic leukocytes (or neutrophils) are the largest population of leukocytes (65 - 75%). Morphological features of neutrophils:

1) segmented nucleus;

2) in the cytoplasm, small granules staining in a slightly oxyphilic (pink) color, among which nonspecific granules can be distinguished - varieties of lysosomes, specific granules. Organelles in leukocytes are not developed. The size in the smear is 10 - 12 microns.

According to the degree of maturity, neutrophils are divided into:

1) young (metamyelocytes) - 0 - 0,5%;

2) stab - 3 - 5%;

3) segmented (mature) - 60 - 65%.

An increase in the percentage of young and stab forms of neutrophils is called a shift of the leukocyte formula to the left and is an important diagnostic indicator. A general increase in the number of neutrophils in the blood and the appearance of young forms are observed in various inflammatory processes in the body. Currently, neutrophilic leukocytes can determine the gender of the blood - in women, one of the segments has a perinuclear satellite (or appendage) in the form of a drumstick.

The life expectancy of neutrophils is 8 days, of which 8-12 hours they are in the blood, and then they enter the connective and epithelial tissues, where they perform their main functions.

Functions of neutrophils:

1) phagocytosis of bacteria;

2) phagocytosis of immune complexes ("antigen - antibody");

3) bacteriostatic and bacteriolytic;

4) release of keyons and regulation of leukocyte reproduction.

Eosinophilic leukocytes (or eosinophils). The content is normal - 1 - 5%. Dimensions in smears - 12 - 14 microns.

Morphological features of eosinophils:

1) there is a two-segment core;

2) large oxyphilic (red) granularity is noted in the cytoplasm;

3) other organelles are poorly developed.

Among the granules of eosinophils, nonspecific azurophilic granules are isolated - a type of lysosome containing the enzyme peroxidase and specific granules containing acid phosphatase. Organelles in eosinophils are poorly developed.

According to the degree of maturity, eosinophils are also divided into young, stab and segmented, but the definition of these subpopulations in clinical laboratories is rarely performed.

Methods for neutralizing histamine and serotonin include phagocytosis and adsorption of these biologically active substances on the cytolemma, the release of enzymes that break them down extracellularly, and the release of factors that prevent the release of histamine and serotonin.

Functions of eosinophils - participation in immunological (allergic and anaphylactic) reactions: inhibit (inhibit) allergic reactions by neutralizing histamine and serotonin.

The participation of eosinophils in allergic reactions explains their increased content (up to 20 - 40% or more) in the blood in various allergic diseases (worm infestations, bronchial asthma, cancer, etc.).

The lifespan of eosinophils is 6-8 days, of which the stay in the bloodstream is 3-8 hours.

Basophilic leukocytes (or basophils). This is the smallest population of granular leukocytes (0,5 - 1%), however, there are a huge number of them in the total mass in the body.

The dimensions in the smear are 11 - 12 microns.

Morphology:

1) a large, weakly segmented nucleus;

2) the cytoplasm contains large granules;

3) other organelles are poorly developed.

The functions of basophils are participation in immune (allergic) reactions through the release of granules (degranulation) and the above biologically active substances contained in them, which cause allergic manifestations (tissue edema, blood filling, itching, spasm of smooth muscle tissue, etc.).

Basophils also have the ability to phagocytosis.

Morphological and functional characteristics of non-granular leukocytes

Agranulocytes do not contain granules in the cytoplasm and are subdivided into two completely different cell populations - lymphocytes and monocytes.

Lymphocytes are the cells of the immune system.

Lymphocytes, with the participation of auxiliary cells (macrophages), provide immunity, i.e., protection of the body from genetically alien substances. Lymphocytes are the only blood cells capable of mitotic division under certain conditions. All other leukocytes are terminal differentiated cells. Lymphocytes are a heterogeneous (heterogeneous) population of cells.

By size, lymphocytes are divided into:

1) small (4,5 - 6 microns);

2) medium (7 - 10 microns);

3) large (more than 10 microns).

In the peripheral blood, up to 90% are small lymphocytes and 10-12% are medium. Large lymphocytes are not normally found in peripheral blood. In electron microscopic examination, small lymphocytes can be divided into light and dark.

Small lymphocytes are characterized by:

1) the presence of a large round nucleus, consisting mainly of heterochromatin, especially in small dark lymphocytes;

2) a narrow rim of basophilic cytoplasm, which contains free ribosomes and weakly expressed organelles - the endoplasmic reticulum, single mitochondria and lysosomes.

Medium lymphocytes are characterized by:

1) a larger and loose nucleus, consisting of euchromatin in the center and heterochromatin along the periphery;

2) in the cytoplasm, in comparison with small lymphocytes, the endoplasmic reticulum and the Golgi complex are more developed, there are more mitochondria and lysosomes.

According to the sources of development, lymphocytes are divided into:

1) T-lymphocytes. Their formation and further development is associated with the thymus (thymus gland);

2) B-lymphocytes. Their development in birds is associated with a special organ (the bag of Fabricius), and in mammals and humans, with its analogue that has not yet been precisely established.

In addition to the sources of development, T- and B-lymphocytes differ among themselves and in their functions.

By function:

1) B-lymphocytes and plasma cells formed from them provide humoral immunity, i.e., protection of the body from foreign corpuscular antigens (bacteria, viruses, toxins, proteins, etc.) contained in the blood, lymphatic fluid;

2) T-lymphocytes, which are divided into the following subpopulations according to their functions: killers, helpers, suppressors.

However, this simple classification is outdated, and it is now accepted to classify all lymphocytes by the presence of receptors (CD) on their membrane. In accordance with this, lymphocytes CD3, CD4, CD8, etc. are isolated.

According to life expectancy, lymphocytes are divided into:

1) short-lived (weeks, months) - mainly B-lymphocytes;

2) long-lived (months, years) - mainly T-lymphocytes.

Monocytes are the largest blood cells (18 - 20 microns), having a large bean-shaped or horseshoe-shaped nucleus and a well-defined basophilic cytoplasm, which contains multiple pinocytic vesicles, lysosomes and other common organelles.

According to their function - phagocytes. Monocytes are not fully mature cells. They circulate in the blood for 2-3 days, after which they leave the bloodstream, migrate to different tissues and organs and turn into various forms of macrophages, the phagocytic activity of which is much higher than that of monocytes. Monocytes and macrophages formed from them are combined into a single macrophage system (or mononuclear phagocytic system (MPS)).

Features of the leukocyte formula in children

In newborns in the general blood test of erythrocytes 6 - 7 x 10¹² per liter - physiological erythrocytosis, the amount of hemoglobin reaches 200 g per 1 liter, leukocytes 10 - 30 x 10⁹ in 1 liter - physiological age-related leukocytosis, the number of platelets is the same as in adults - 200 - 300 x 10⁹ in l.

After birth, the number of red blood cells and hemoglobin gradually decreases, first reaching adult levels (5 million in 1 μl), and then physiological anemia develops. The level of red blood cells and hemoglobin reaches adult levels only during puberty. The white blood cell count decreases to 2 - 10 x 15 10 weeks after birth⁹ in 1 liter, and by the period of puberty reaches the values ​​of an adult.

The greatest changes in the leukocyte formula in children are noted in the content of lymphocytes and neutrophils. The remaining indicators do not differ from the values ​​of adults.

At birth, the ratio of neutrophils and lymphocytes is similar to that of adults - 65 - 75% to 20 - 35%. In the first days of a child's life, there is a decrease in the concentration of neutrophils and an increase in the content of lymphocytes, on the 4th - 5th day their number is compared - 45% each (first physiological crossover). Further, physiological lymphocytosis is observed in children - up to 65% and physiological neutropenia - 25%, the lowest neutrophil counts are observed by the end of the second year of life. After that, a gradual increase in the content of neutrophils and a decrease in the concentration of lymphocytes begin, at the age of 4-5 years, a second physiological crossover is observed. By puberty, the ratio of neutrophils and lymphocytes comes to the level of an adult.

The constituent components and functions of lymph

Lymph consists of lymphoplasm and formed elements, mainly lymphocytes (98%), as well as monocytes, neutrophils, and sometimes erythrocytes. Lymphoplasma is formed by the penetration of tissue fluid into the lymphatic capillaries, and then discharged through the lymphatic vessels of various calibers and flows into the venous system. Along the way, lymph passes through the lymph nodes, in which it is cleared of exogenous and endogenous particles, and is also enriched with lymphocytes.

Functions of the lymphatic system:

1) tissue drainage;

2) enrichment with lymphocytes;

3) purification of the lymph from exogenous and endogenous substances.

Authors: Selezneva T.D., Mishin A.S., Barsukov V.Yu.

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