Active blood reaction. Blood buffer system. When to donate blood: preparation for the test

Blood is a liquid internal environment body, more precisely - to the extracellular fluid, even more precisely - to the blood plasma circulating in the vascular system and cells suspended (suspended) in the plasma. Clotted (coagulated) blood consists of a clot (thrombus), which includes cellular elements and some plasma proteins, and a clear liquid similar to plasma, but devoid of fibrinogen (serum). The blood system includes hematopoietic organs (hematopoiesis) and peripheral blood, both its circulating and deposited (reserved) fractions in organs and tissues. Blood is one of the integrating systems of the body. Various deviations in the state of the body and individual organs lead to changes in the blood system, and vice versa. That is why, when assessing a person’s state of health or illness, they carefully examine the parameters characterizing the blood (hematological parameters).

Blood functions

The numerous functions of blood are determined not only by the properties inherent in the blood itself (plasma and cellular elements), but also by the circumstances that the blood circulates in vascular system, permeating all tissues and organs, and is in constant exchange with the interstitial fluid that washes all the cells of the body. In the very general view blood functions include transport, homeostatic, protective and hemocoagulation. As part of the internal environment of the body, blood is an integral part of almost any functional activity (for example, blood participation in respiration, nutrition and metabolism, excretion, hormonal and temperature regulation, regulation acid-base balance and volume of fluids, the implementation of immune reactions).

Blood volumes

Total blood volume It is customary to calculate based on body weight (excluding fat), which is approximately 7% (6-8%, for newborns - 8.5%). So, in an adult man weighing 70 kg, the blood volume is about 5600 ml. In this case, 3.5-4 l usually circulates in vascular bed and cavities of the heart (circulating blood fraction, or BCC- circulating blood volume) and 1.5-2 liters are deposited in the vessels of organs abdominal cavity, lungs, subcutaneous tissue and other fabrics (deposited fraction). Plasma volume is approximately 55% total volume blood, cellular elements- 45% (36-48%) of the total blood volume.

Hematocrit(Ht, or hematocrit number) - the ratio of the volume of cellular elements of the blood (99% is erythrocytes) to the volume of plasma - is normally 0.41-0.50 for men, 0.36-0.44 for women. Blood volume is determined directly (by labeling red blood cells with 51 Cr) or indirectly (by labeling plasma albumin with 131 I or determining hematocrit).

Rheological properties

Rheological (including viscous) properties of blood are important when it is necessary to assess the movement of blood in vessels and the suspension stability of red blood cells.

Viscosity- property of a liquid that affects the speed of its movement. Blood viscosity is determined 99% by red blood cells. Resistance to blood flow (according to Poiseuille's law) is directly proportional to viscosity, and viscosity is directly proportional to hematocrit. Thus, an increase in hematocrit means an increase in the load on the heart(i.e., there is an increase in the volume of filling and ejection of the heart).

Suspension stability of erythrocytes. Red blood cells repel each other because they have a negative charge on their surface. A decrease in the surface negative charge of erythrocytes causes their aggregation; such aggregates are less stable in the gravitational field, since their effective density is increased. Erythrocyte sedimentation rate(ESR) is a measure of the suspension stability of red blood cells. The ESR value is measured using graduated capillary pipettes, and to prevent blood clotting, trisodium citrate (so-called citrated blood) is added to it.

Within an hour, a light column of plasma appears in the upper part of the capillary tube, the height of which in millimeters is the ESR value (in healthy individuals 2-15 mm/h). Most typical reason increasing ESR- inflammation of various origins (bacterial, autoimmune), pregnancy, tumor diseases, which leads to changes in the protein composition of the blood plasma (ESR is especially “accelerated” by an increase in the content of fibrinogen and partly γ-globulins).

PLASMA

The supernatant formed after centrifugation of clotted blood is blood serum. Supernatant after centrifugation of whole blood with anticoagulants added to it (citrated blood, heparinized blood) - plasma blood. Unlike plasma, serum does not contain a number of plasma blood coagulation factors (I - fibrinogen, II - prothrombin, V - proaccelerin and VIII - antihemophilic factor). Plasma is a pale amber liquid containing proteins, carbohydrates, lipids, lipoproteins, electrolytes, hormones and others. chemical compounds. The volume of plasma is about 5% of body weight (with a weight of 70 kg - 3500 ml) and 7.5% of all body water. Blood plasma consists of water (90%) and substances dissolved in it (10%, organic - 9%, inorganic - 1%; in the solid residue, proteins account for approximately 2/3, and 1/3 are low molecular weight substances and electrolytes) . Chemical composition plasma is similar to interstitial fluid (the predominant cation is Na +, the predominant anions are Cl -, HCO 3 -), but the protein concentration in plasma is higher (70 g/l).

Squirrels

Plasma contains several hundred different proteins, coming mainly from the liver, but also from cellular elements circulating in the blood and from many extravascular sources. The functions of plasma proteins are extremely diverse.

Classifications.Plasma proteins are classified according to physicochemical characteristics (more precisely, according to their mobility in an electric field), as well as depending on the functions they perform.

Electrophoretic mobility. Five electrophoretic fractions of plasma proteins were isolated: albumins and globulins (α 1 - and α 2 -, β- and γ-).

Φ Albumin(40 g/l, M r ~ 60-65 kD) largely determine oncotic (colloid-osmotic) pressure(25 mmHg, or 3.3 kPa) blood (5 times the oncotic pressure intercellular fluid. That is why, with massive loss of albumin (hypoalbuminemia), “renal” edema develops through the kidneys, and during fasting, “hungry” edema develops.

Φ Globulins(30 g/l), including (examples):

♦ a^globulins: a 1 -antitrypsin, a 1 -lipoproteins ( high density), prothrombin;

♦ a 2 -globulins: a 2 -macroglobulin, a 2 -antithrombin III, a 2 -haptoglobulin, plasminogen;

♦ β-globulins: β-lipoproteins (low density), apoferritin, hemopexin, fibrinogen, C-reactive protein;

♦ γ-globulins: immunoglobulins (IgA, IgD, IgE, IgG, IgM). Functional classification. There are three main groups: 1) proteins of the blood coagulation system; 2) proteins involved in immune reactions; 3) transport proteins.

Φ 1. Proteins of the blood coagulation system(see details below). There are coagulants and anticoagulants. Both groups of proteins provide balance between the processes of clot formation and destruction.

♦ Coagulants(primarily plasma coagulation factors) are involved in the formation of a blood clot, for example fibrinogen (synthesized in the liver and turns into fibrin during hemocoagulation).

♦ Anticoagulants- components of the fibrinolytic system (prevent clotting).

Φ 2. Proteins involved in immune reactions. This group includes Ig (for more details, see Chapter 29) and proteins of the complement system.

Φ 3. Transport proteins- albumins ( fatty acid), apolipoproteins (cholesterol), transferrin (iron), haptoglobin (Hb), ceruloplasmin (copper), transcortin (cortisol), transcobalamins (vitamin B 12) and many others

Lipoproteins

In blood plasma, cholesterol and triglycerides form complexes with proteins. So different in size and other signs the complexes are called lipoproteins (LP). Cholesterol transport is carried out by low-density lipoproteins (LDL), very low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), high-density lipoproteins (HDL), and chylomicrons. From a clinical point of view (the likelihood of developing arteriosclerotic lesions - atherosclerosis), the content of cholesterol in the blood and the ability of the drug to be fixed in the arterial wall (atherogenicity) are of significant importance.

HDL - the smallest LP in size (5-12 nm) - easily penetrates the arterial wall and leaves it just as easily, i.e. HDL is not atherogenic.

LDL (18-25 nm), intermediate density LDL (25-35 nm) and a few VLDL (about 50 nm in size) are too small to penetrate the arterial wall. After oxidation, these drugs are easily retained in the arterial wall. It is these categories of drugs that are atherogenic.

Large LPs - chylomicrons (75-1200 nm) and VLDL of significant size (80 nm) - are too large to penetrate into the arteries and are not regarded as atherogenic.

Osmotic and oncotic pressure

Osmolytes contained in plasma (osmotically active substances), i.e. electrolytes of low molecular weight (inorganic salts, ions) and high molecular weight substances (colloidal compounds, mainly proteins) determine the most important properties of blood - osmotic and oncotic pressure. IN medical practice these parameters are important not only in relation to blood per se(for example, the idea that solutions are isotonic), but also for a real situation in vivo(for example, to understand the mechanisms of water transfer through the capillary wall between blood and intercellular fluid, in particular the mechanisms of the development of edema, separated by the equivalent of a semi-permeable membrane - the capillary wall). In this context for clinical practice Parameters such as effective hydrostatic and central venous pressure.

Φ Osmotic pressure(π, see more in Chapter 3, including Fig. 2-9) - excess hydrostatic pressure on a solution separated from the solvent (water) by a semi-permeable membrane, at which diffusion of the solvent through the membrane stops (under conditions in vivo it is the vascular wall). Blood osmotic pressure can be determined by its freezing point (i.e., cryoscopically); normally it is 7.5 atm (5800 mmHg, 770 kPa, 290 mOsmol/kg water).

Φ Oncotic pressure(colloid osmotic pressure - COP) - pressure that arises due to the retention of water in the vascular bed by blood plasma proteins. At normal content plasma protein (70 g/l) plasma CODE - 25 mm Hg. (3.3 kPa), while the COD of the interstitial fluid is much lower (5 mm Hg, or 0.7 kPa).

Φ Effective hydrostatic pressure- the difference between the hydrostatic pressure of the intercellular fluid (7 mm Hg) and the hydrostatic pressure of blood in the microvessels. Normally, the effective hydrostatic pressure in the arterial part of the microvessels is 36-38 mm Hg, and in the venous part - 14-16 mm Hg.

Φ Central venous pressure- blood pressure inside venous system(in the superior and inferior vena cava), normally 4-10 cm of water column. Central venous pressure decreases with a decrease in blood volume and increases with heart failure and stagnation in the circulatory system. Infusion solutions

Saline infusion solutions for intravenous administration must have the same osmotic pressure as plasma, i.e. be isosmotic (isotonic, for example the so-called saline- 0.85% sodium chloride solution).

Acid-base balance, including buffer systems blood, discussed in Chapter 28.

CELL ELEMENTS OF BLOOD

To blood cells (obsolete name - shaped elements) include red blood cells, white blood cells and platelets, or blood platelets (Fig. 24-1). Blood cells are studied microscopically

Rice. 24-1. Blood cells. Blood contains three types of cells: erythrocytes (non-nucleated cells shaped like a biconcave disk), leukocytes (nuclear spherical cells containing various types of granules) and platelets (fragments of the cytoplasm of giant cells located in the bone marrow - megakaryocytes). A - erythrocyte; B - neutrophil; B - eosinophil; G - basophil; D - lymphocytes (small and large); E - monocyte; F - platelets.

on smears stained according to Romanovsky-Giemsa, Wright, etc. Contents in peripheral blood adult human red blood cells in men - 4.5-5.7 x 10 12 / l (in women - 3.9-5 x 10 12 / l), leukocytes - 3.8-9.8 x 10 9 / l (lymphocytes - 1.2-3 .3x10 9 /l, monocytes - 0.2-0.7x10 9 /l, granular leukocytes - 1.8-6.6x10 9 /l), platelets - 190-405x10 9 /l. Definitive forms of cells circulate in the peripheral blood, the formation of which (hematopoiesis, or hematopoiesis) occurs in the red bone marrow and organs of the lymphoid system (thymus, spleen, The lymph nodes and lymphoid follicles). From the hematopoietic stem cell in the red bone marrow, erythroid cells are formed (red blood cells and reticulocytes enter the blood), myeloid cells (granular leukocytes, rod- and segmented neutrophil leukocytes, mature basophilic and eosinophilic leukocytes enter the blood), monocytes, blood platelets and some lymphocytes , in the organs of the lymphoid system - T- and B-lymphocytes.

Hematopoiesis

Hematopoiesis is the formation from a hematopoietic stem cell of precursor cells of specific hematopoiesis, their production

proliferation and differentiation, as well as maturation of blood cellular elements under specific microenvironment conditions and under the influence of hematopoietic factors. In the prenatal period, hematopoiesis occurs in several developing organs (see Chapter 20). Hematopoiesis after birth, in children, adolescents and adults, occurs in the bone marrow of flat bones (skull, ribs, sternum, vertebrae, pelvic bones) and epiphyses of tubular bones, and hematopoietic organs for lymphocytes are the spleen, thymus, lymph nodes, lymphoid follicles in various organs.

Mature peripheral blood cells develop from precursors that mature in the red bone marrow. The unitary theory of hematopoiesis (Fig. 24-2) provides that the ancestor of all cellular elements of the blood is hematopoietic stem cell. Her descendants are pluripotent progenitor cells lymphocytopoiesis (CFU-Ly) and myelopoiesis (CFU-GEMM). As a result of the division of CFU-Ly and CFU-GEMM, their descendants remain

Rice. 24-2. Scheme of hematopoiesis. CFU-GEMM - pluripotent myelopoiesis progenitor cell; CFU-Ly - pluripotent lymphocytopoiesis progenitor cell; CFU-GM - pluripotent cell precursor of granulocytes and monocytes; CFU-G is a pluripotent progenitor cell of neutrophils and basophils. BFU-E and CFU-E are unipotent erythrocyte precursors; CFU-Eo - eosinophils; CFU-M - monocytes; CFU-Meg - megakaryocytes. CFU (Colony Forming Unit) - colony-forming unit (CFU), BFU - Burst Forming Unit - explosion-forming unit.

pluripotent or turn into committed (predetermined by fate) unipotent progenitor cells, also capable of dividing, but differentiating (developing) only in one direction. Proliferation of unipotent progenitor cells is stimulated colony-stimulating factors And interleukins(especially interleukin-3).

Erythropoiesis. Beginning of the erythroid series - stem cell erythropoiesis, or burst-forming unit (BFU-E), from which the unipotent precursor of erythrocytes (CFU-E) is formed. The latter gives rise to the proerythroblast. As a result of further differentiation, the Hb content increases and the nucleus is lost. From the proerythroblast, erythroblasts successively develop through proliferation and differentiation: basophilic- polychromatophilic- oxyphilic (normoblast) and then non-dividing forms - reticulocyte and erythrocyte. From BFU-E to normoblast is 12 cell generations, and from CFU-E to late normoblast is 6 or fewer cell divisions. The duration of erythropoiesis (from its BFU-E stem cell to an erythrocyte) is 2 weeks. The intensity of erythropoiesis is controlled by erythropoietin. The main stimulus for the production of erythropoietin is a decrease in the oxygen content in the blood (pO 2) - hypoxia (Fig. 24-3).

Granulocytopoiesis(Fig. 24-4). Granulocytes are formed in the bone marrow. Neutrophils and basophils are derived from the pluripotent neutrophil and basophil precursor cell (CFU-G), and eosinophils are derived from the unipotent eosinophil precursor (CFU-Eo). CFU-G and CFU-Eo are descendants of the pluripotent granulocyte-monocyte progenitor cell (CFU-GM). During the development of granulocytes, the following stages can be distinguished: myeloblasts- promyelocytes - myelocytes - metamyelocytes - band and segmented granulocytes. Specific granules appear at the myelocyte stage; from this point on, the cells are named according to the type of mature granulocytes they produce. Cell division stops at the metamyelocyte stage. The proliferation and differentiation of progenitor cells is controlled by colony-stimulating factors (granulocytes and macrophages - GM-CSF, granulocytes - G-CSF), IL-3 and IL-5 (eosinophil precursors).

Rice. 24-3. Regulation of erythropoiesis . Proliferation of the burst-forming unit of erythropoiesis (BFU-E) is stimulated by interleukin-3. The unipotent erythrocyte precursor CFU-E is sensitive to erythropoietin. The most important stimulus for the formation of red blood cells is hypoxia, which triggers the synthesis of erythropoietin in the kidney, and in the fetus, in the liver. Erythropoietin is released into the blood and enters the bone marrow, where it stimulates the proliferation and differentiation of unipotent erythrocyte precursor (CFU-E) and the differentiation of subsequent erythroid cells. As a result, the number of red blood cells in the blood increases. Accordingly, the amount of oxygen entering the kidney increases, which inhibits the formation of erythropoietin.

Monocytopoiesis. Monocytes and granulocytes share a common progenitor cell, the colony-forming unit of granulocytes and monocytes (CFU-GM), which is derived from a pluripotent myelopoiesis progenitor cell (CFUGEMM). There are two stages in the development of monocytes - monoblast and promonocyte.

Thrombocytopoiesis. The largest (30-100 µm) bone marrow cells, megakaryocytes, develop from megakaryoblasts. During differentiation, the megakaryocyte increases in size and its nucleus becomes lobulated. A developed system of demarcation membranes is formed, along which platelets are separated (“unlaced”) (Fig. 24-5). The proliferation of megakaryocyte precursors - megakaryoblasts - is stimulated by thrombopoietin synthesized in the liver.

Lymphopoiesis. From a hematopoietic stem cell (CFU-blast) comes a pluripotent lymphatic precursor cell.

Rice. 24-4. Granulocytopoiesis. During the differentiation of granulocyte precursors, myeloblast, promyelocyte, myelocyte, metamyelocyte, band and segmented granulocytes are isolated.

Rice. 24-5. Platelet formation . The megakaryocyte located in the bone marrow forms a proplatelet pseudopodia. The latter penetrates through the capillary wall into its lumen. Platelets are separated from the pseudopodia and enter the bloodstream.

poetry (CFU-Ly), which subsequently gives rise to B-lymphopoiesis progenitor cells, T-lymphopoiesis and (partially) NK cell progenitors. The early precursors of B lymphocytes are formed in the bone marrow, and T lymphocytes in the thymus. Further differentiation includes levels of pro-B(T) cells, pre-B(T) cells, immature B(T) cells, mature (“naive”) B(T) cells and (after exposure to Ag ) - mature B(T) cells in the final stages of differentiation. IL-7 produced by bone marrow stromal cells promotes the formation of T and B lymphocytes by acting on their precursor cells. Unlike other blood cells, lymphocytes can proliferate outside the bone marrow. It occurs in immune system tissues in response to stimulation.

Red blood cells

From the red bone marrow, predominantly immature red blood cells enter the blood - reticulocytes. They (unlike mature red blood cells) contain ribosomes, mitochondria and the Golgi complex. Final differentiation into erythrocytes occurs within 24-48 hours after the release of reticulocytes into the bloodstream. The number of reticulocytes entering the bloodstream is normally equal to the number of red blood cells removed. Reticulocytes make up about 1% of all circulating red blood cells. Red blood cells(see Fig. 24-1, A) - anucleate cells with a diameter of 7-8 microns (normocytes). The number of red blood cells in women is 3.9-4.9x10 12 /l, in men - 4.0-5.2x10 12 /l. More high content red blood cells in men is due to the erythropoiesis-stimulating influence of androgens. Lifespan(blood circulation time) 100-120 days.

Shape and dimensions.An erythrocyte in the blood has the shape of a biconcave disk with a diameter of 7-8 microns. It is believed that it is this configuration that creates the largest surface area in relation to volume, which ensures maximum gas exchange between blood plasma and red blood cells. With any other form of red blood cells, they speak of poikilocytosis. Dispersion of erythrocyte sizes is anisocytosis, cells with a diameter of more than 9 microns are macrocytes, less than 6 microns are microcytes. In a number of blood diseases, the size and shape of red blood cells change, and their osmotic resistance decreases, which leads to the destruction (hemolysis) of red blood cells.

Age-related changes in red blood cells. At birth and in the first hours of life, the number of red blood cells in the blood is increased and amounts to 6.0-7.0x10 12 / l. In newborns, anisocytosis with a predominance of macrocytes is observed, as well as increased content reticulocytes. During the first day of the postnatal period, the number of red blood cells decreases, by the 10-14th day it reaches the adult level and continues to decrease. The minimum indicator is observed in the 3-6th month of life (physiological anemia), when the level of erythropoietin is reduced. This is due to a decrease in the synthesis of erythropoietin in the liver and the beginning of its production in the kidney. At the 3-4th year of life, the number of red blood cells is reduced (lower than in an adult), i.e. 1 liter contains less than 4.5x10 12.

Rice. 24-6. Perimembrane cytoskeleton of the erythrocyte . Band 3 protein is a major transmembrane protein. The spectrin-actin complex forms a network-like structure of the perimembrane cytoskeleton. Band 4.1 protein is associated with the spectrin-actin complex, stabilizing it. Ankyrin, through band 3 protein, connects the spectrin-actin complex to the cell membrane. The names of protein bands characterize their electrophoretic mobility.

Plasmolemma and perimembrane cytoskeleton. The cell membrane of an erythrocyte is quite plastic, which allows the cell to deform and easily pass through narrow capillaries (their diameter is 3-4 microns). The main transmembrane proteins of the erythrocyte are band 3 protein and glycophorins. Protein stripe 3(Fig. 24-6) together with the proteins of the near-membrane cytoskeleton (spectrin, ankyrin, fibrillar actin, band 4.1 protein) ensures the maintenance of the shape of the erythrocyte in the form of a biconcave disk. Glycophorins- membrane glycoproteins, their polysaccharide chains contain Ag determinants (for example, agglutinogens A and B of the AB0 blood group system).

Hemoglobin

Almost the entire volume of the red blood cell is filled with respiratory protein - hemoglobin(Hb). The Hb molecule is a tetramer, consisting

consisting of four subunits - polypeptide chains of globin (two chains α and two chains β, γ, δ, ε, θ, ζ in different combinations), each of which is covalently linked to one heme molecule. Heme built from four molecules pyrrole, forming a porphyrin ring, in the center of which there is an iron atom (Fe 2 +). The main function of Hb is the transport of O 2. There are several types of Hb produced by different dates development of the organism, differing in the structure of globin chains and affinity for oxygen. Fetal Hb(ζ- and ε-chains) appear in a 19-day embryo and are contained in erythroid cells in the first 3-6 months of pregnancy. Fetal Hb(HbF - α 2 γ 2) appears in the 8-36th week of pregnancy and makes up 90-95% of the total Hb of the fetus. After birth, its amount gradually decreases and by 8 months it is 1%. Definitive Hb- the main Hb of adult human erythrocytes (96-98% - HbA (A 1,) - α 2 β 2, 1.5-3% - HbA 2 - α 2 δ 2). More than 1000 mutations of different globins are known, significantly changing the properties of Hb, primarily the ability to transport O 2.

Forms of hemoglobin. In erythrocytes, Hb is found in reduced (HbH) and/or oxidized (HbO 2) forms, as well as in the form of glycosylated Hb. In some cases, the presence of carboxyhemoglobin and methemoglobin is possible.

F Oxyhemoglobin. In the lungs, with increased pO 2, Hb binds (associates) O 2, forming oxyhemoglobin (HbO 2). In this form, HbO 2 carries O 2 from the lungs to the tissues, where the O 2 is easily released (dissociated) and the HbO 2 becomes deoxygenated by Hb (referred to as HbH). For the association and dissociation of O 2, it is necessary that the heme iron atom be in a reduced state (Fe 2 +). When ferric iron (Fe 3 +) is included in heme, methemoglobin is formed - a very poor transporter of O 2. F Methemoglobin(MetHb) - Hb containing Fe heme in trivalent form (Fe 3 +) does not tolerate O 2; strongly binds O 2, so the dissociation of the latter is difficult. This leads to methemoglobinemia and inevitable gas exchange disorders. MetHb formation can be hereditary or acquired. IN the latter case this is the result of exposure of red blood cells to strong oxidizing agents. These include nitrates and inorganic nitrites, sulfonamides and local anesthetics (for example, lidocaine).

Φ Carboxyhemoglobin- poor oxygen carrier. Hb binds more easily (about 200 times) than with O2 to carbon monoxide CO ( carbon monoxide), forming carboxyhemoglobin (O 2 is replaced by CO).

Φ Glycosylated Hb(HbA 1C) - HbA (A1:), modified by the covalent addition of glucose to it (normal HbA 1C 5.8-6.2%). One of the first signs of diabetes mellitus is an increase in the amount of HbA 1C by 2-3 times. This Hb has a worse affinity for oxygen than regular Hb.

Oxygen transport. Blood transports about 600 liters of O2 from the lungs to the tissues every day. The main volume of O 2 is transported by HbO 2 (O 2 is reversibly associated with Fe 2 + heme; this is the so-called chemically bound O 2 - an essentially incorrect, but, unfortunately, well-established term). A small part of O 2 is dissolved in the blood (physically dissolved O 2). The O2 content in the blood depending on the partial pressure of O2 (Po2) is shown in Fig. 24-7.

A gas physically dissolved in the blood. According to Henry's law, the amount of O 2 (any gas) dissolved in the blood is proportional to Po 2 (the partial pressure of any gas) and the solubility coefficient of the particular gas. The physical solubility of O 2 in the blood is approximately 20 times less than the solubility of CO 2, but for both gases it is insignificant. At the same time, the gas physically dissolved in the blood is necessary stage transport of any gas (for example, when O 2 moves into an erythrocyte from the cavity of the alveoli).

Oxygen capacity blood- the maximum possible amount associated with HbO 2 is theoretically 0.062 mmol O 2 (1.39 ml O 2) per 1 g of Hb (the real value is slightly less - 1.34 ml O 2 per 1 g of Hb). The measured values ​​are for men 9.4 mmol/l (210 ml O 2 /l), for women 8.7 mmol/l (195 ml O 2 /l).

Saturation(saturation, S) Hb() 2(So ​​2) depends on the partial pressure of oxygen (Po 2) and actually reflects the content of oxygenated Hb (HbO 2, see curve A in Fig. 24-7). So 2 can take values ​​from 0 ( Hb() 2 no) to 1 (no HbH). At half saturation (S 05) Po 2 is equal to 3.6 kPa (27 mm Hg), at S 075 - 5.4 kPa, at S 0 98 1 3, 3 kPa. In other words-

Oxygen partial pressure (mmHg)

Rice. 24-7. Blood oxygen content . A - associated with HbO 2. B - O 2 physically dissolved in the blood. Please note that curve A (unlike curve B) is not linear; it is a so-called S-shaped (sigmoid) curve; This shape of the curve reflects the fact that the four Hb subunits bind to O 2 cooperatively. This circumstance has important physiological significance: at specific and different (!) values ​​of Po 2 in arterial and mixed (venous) blood, the most favorable conditions for the association of Hb and O 2 in the lung capillaries and for the dissociation of Hb and O 2 in tissue capillaries. At the same time, only a small part of O 2 is physically dissolved in the blood plasma (maximum 6%); the physical solubility of O 2 is described by Henry's law: with an increase in Po 2, the O 2 content increases linearly.

mi (see curve A in Fig. 24-7), the relationship between So 2 and Po 2 is not linear (characteristic S-shaped curve), which favors not only the binding of O 2 in the lungs (arterial blood) and the transport of O 2, but also the release of O 2 in blood capillaries organs and tissues, since the saturation of arterial blood with oxygen (S a o 2) is approximately 97.5%, and the saturation venous blood(S v o 2) - 75%. Affinity of Hb to O2, those. saturation Hb() 2 for a specific

Po 2 changes a number of factors (temperature, pH and Pco 2, 2,3-biphos-

foglycerate; rice. 24-8).

pH, Pwith 2 and the Bohr effect. The influence of pH is especially significant: decrease pH value (shift to the acidic side)

Rice. 24-8. Dissociation of oxyhemoglobin in the blood depending on Po 2 . Depending on changes (indicated by arrows) in blood temperature, pH, Pco 2 and red blood cell 2,3-bisphosphoglycerate concentration, the hemoglobin O 2 saturation curve shifts to the right (meaning less oxygen saturation) or left (meaning more oxygen saturation). The position corresponding to half saturation (S 05) is marked with a circle on the curve.

well - into the acidosis zone) shifts the Hb dissociation curve to the right (which promotes the dissociation of O 2), whereas increase pH (shift to the alkaline side - to the zone of alkalosis) shifts the Hb dissociation curve to the left (which increases the O2 affinity). The effect of Pco 2 on the dissociation curve of oxyhemoglobin is carried out primarily through a change in the pH values: when Co 2 enters the blood, the pH decreases, which promotes the dissociation of O 2 and its diffusion from the blood into the tissues. On the contrary, in the lungs CO 2 diffuses from the blood into the alveoli, which causes an increase in pH, i.e. promotes the binding of O 2 to Hb. This effect of CO 2 and H+ on the affinity of O 2 for Hb is known as Christian Bohr effect(father of the great physicist Niels Bohr). Thus, the Bohr effect is primarily due to changes in pH with increasing Co 2 content and only partially due to the binding of Co 2 to Hb (see below). The physiological consequence of the Bohr effect is facilitating the diffusion of o 2 from the blood into tissues and the binding of o 2 arterial blood in the lungs.

Temperature. The effect of temperature on the affinity of Hb for O2 in homeothermic animals is theoretically unimportant, but may be important in a number of situations. Thus, with intense muscle load, body temperature rises, as a result of which the dissociation curve shifts to the right (the intake of O 2 into the tissue increases). When the temperature drops (especially fingers, lips, auricle) the dissociation curve shifts to the left, i.e. O 2 affinity increases; therefore, the supply of O 2 to the tissues does not increase.

2,3-Bisphosphoglycerate(BPG), an intermediate product of glycolysis, is found in erythrocytes in approximately the same molar concentration as Hb. BPG binds to Hb (mainly due to interaction with the β-subunit, i.e. with definitive Hb, but not with fetal Hb, which does not contain the β-subunit). The binding of BPG to Hb shifts the Hb dissociation curve to the right (see Fig. 24-8), which promotes the dissociation of O 2 at moderate Po 2 values ​​(for example, in tissue capillaries), but has virtually no effect on the dissociation curve at high Po 2 values ​​( in the capillaries of the lung). It is significant that with increased glycolysis (anaerobic oxidation), the concentration of BPG in erythrocytes increases, playing

the role of a mechanism that adapts the body to hypoxia, which is observed in lung diseases, anemia, and elevation. Thus, during the period of adaptation to high altitudes (more than 4 km above sea level), the concentration of BPG increases almost 2 times after 2 days (from 4.5 to 7.0 mM). It is clear that this reduces the affinity of Hb for O 2 and increases the amount of O 2 released from the capillaries into the tissue. T transport CO2. Like O 2, CO 2 is transported by the blood both in a physically dissolved and chemically bound state (in the composition of bicarbonates and in combination with proteins, i.e. in the form of carbamates, including in connection with Hb - carbohemoglobin). In all three states (dissolved, bicarbonate, carbamates), CO 2 is contained in both erythrocytes (89%) and blood plasma (11%). The chemical bonding of CO 2 produces a significant amount of protons (H+).

Approximately 2/3 of CO 2 (68%, including 63% in red blood cells) is transported in the blood in the form of bicarbonate (HCO 3 -). A fifth of CO 2 (22%, including in the form of carbohemoglobin - 21%) is transferred by carbamates (CO 2 is reversibly attached to the non-ionized terminal α-amino groups of proteins, forming the R-NH-COO - group). 10% of CO 2 is in a dissolved state (equally in plasma and erythrocytes). It is extremely important that in reactions of chemical binding of CO 2 H+ ions are formed:

CO 2 + H 2 O ↔ H 2 CO 3 ↔ H++ HCO 3 - , R-NH 2 + CO 2 ↔ R-NH-COO - + H+.

Φ From both equilibrium reactions it follows that the chemical binding of CO 2 occurs with the formation of H+ ions. Thus, for chemical binding of CO 2 it is necessary to neutralize H+. This problem is solved by the hemoglobin buffer system.

Hemoglobin buffer system (binding of H+ ions) is important for the transport of CO 2 in the blood.

In capillaries great circle blood circulation HbO 2 releases oxygen, and CO 2 enters the blood. In erythrocytes, under the influence of carbonic anhydrase, CO 2 interacts with H 2 O, forming carbonic acid (H 2 CO 3), which dissociates into HCO 3 - and H +. The H+ ion binds to Hb (reduced Hb - HHb is formed), and HCO 3 - from the erythrocytes enters the blood plasma; in return, an equivalent amount enters the red blood cells

Rice. 24-9. Transfer of O 2 and CO 2 with blood . A - influence of CO 2 and H+ on the release of O 2 from the complex with hemoglobin in tissues (Bohr effect); B - oxygenation of deoxyhemoglobin in the lungs, formation and release of CO 2.

Rice. 24-10. Mechanisms of CO 2 transport in blood .

Cl - . At the same time, part of the CO 2 binds to Hb (carbohemoglobin is formed). In the capillaries of the lungs(i.e., under conditions of low pCO 2 and high pO 2) Hb adds O 2 and oxyhemoglobin (HbO 2) is formed. At the same time, CO 2 is released as a result of the rupture of carbamine bonds. In this case, HCO 3 - from the blood plasma enters the erythrocytes (in exchange for Cl - ions) and interacts with H +, split off from Hb at the time of its oxygenation. The resulting carbonic acid (H 2 CO 3) under the influence of carbonic anhydrase is split into CO 2 and H 2 O. CO 2 diffuses into the alveoli and is excreted from the body. CO 2 dissociation curve shows the relationship between blood CO 2 and pCO 2 levels. Unlike the dissociation curve of Hb and O 2 (see Fig. 24-7), the dissociation curve of CO 2 at physiological values ROD 2 (arterial blood - 40 mm Hg, venous blood - 46 mm Hg) is linear. Moreover, at any pCO 2 value, the CO 2 content in the blood is inversely proportional to pO 2 (Hb0 2 saturation). This inverse relationship between CO 2 content and oxygen partial pressure ^O 2) is known as Haldane effect. Like the Bohr effect, the Haldane effect has important physiological significance. Thus, in the capillaries of the systemic circulation, as O 2 diffuses from the capillaries increases the ability of the blood to absorb CO 2, as a result, CO 2 enters the blood. On the contrary, in the capillaries of the lung, when the blood is oxygenated, its ability to absorb CO 2 decreases, as a result, CO 2 is “dumped” into the alveoli.

HEMOGLOBIN METABOLISM

Removing red blood cells from the bloodstream occurs in three ways: 1) by phagocytosis, 2) as a result of hemolysis and 3) during thrombus formation.

Hemoglobin breakdown. With any type of destruction of red blood cells, Hb breaks down into heme and globins (Fig. 24-11). Globins, like other proteins, are broken down into amino acids, and the destruction of heme releases iron ions, carbon monoxide (CO) and protoporphyrin (verdoglobin, from which biliverdin is formed, which is reduced to bilirubin). Bilirubin in combination with albumin, it is transported to the liver, from where it enters the intestine as part of bile, where it is converted into urobiol.

Rice. 24-11. Exchange of hemoglobin and bilirubin .

linogens. The conversion of heme to bilirubin can be observed in a hematoma: the purple color caused by heme slowly passes through the green colors of verdoglobin into yellow bilirubin.

Hematins.Under certain conditions, hydrolysis of Hb causes the formation of hematins (hemomelanin, or malarial pigment, and hydrochloric acid hematin).

IRON METABOLISM

Iron is involved in the functioning of all body systems. The daily requirement for iron is 10 mg for men, 18 mg for women (during pregnancy and lactation - 38 and 33 mg, respectively). The total amount of iron (mainly in combination with

Rice. 24-12. Diagram of iron (Fe) metabolism in the body healthy man with a body weight of 70 kg .

heme Hb) in the body - about 3.5 g (in women - 3 g). Iron is absolutely necessary for erythropoiesis. There are cellular, extracellular iron and iron stores (Fig. 24-12).

The bulk of the body's iron is part of heme (Hb, myoglobin, cytochromes). Some iron is stored in the form of ferritin (in hepatocytes, bone marrow and spleen macrophages) and hemosiderin (in von Kupffer cells of the liver and bone marrow macrophages). A certain amount is in a labile state due to transferrin. Iron, necessary for heme synthesis, is extracted primarily from destroyed red blood cells. Sources of iron- intake from food and destroyed red blood cells.

Iron from food absorbed in the intestines duodenum and the initial section of the jejunum. Iron is absorbed predominantly in divalent form (Fe 2 +). The absorption of Fe 2 + in the gastrointestinal tract is limited and controlled by its concentration in the blood plasma (the ratio of proteins - iron-free apoferritin and ferritin). Absorption is enhanced by ascorbic, succinic, pyruvic acid, sorbitol, and alcohol; suppress - oxalates, calcium supplements and calcium-containing foods (for example, cottage cheese, milk, etc.). On average, 10 mg of iron is absorbed per day. In the gastrointestinal tract, iron accumulates in the epithelial cells of the mucous membrane small intestine. From here transferrin transfers iron to red Bone marrow(for erythropoiesis, this is only 5% of absorbed Fe 2 +), into the liver, spleen, muscles and other organs (for storage).

Iron of dead red blood cells with the help of transferrin, it enters the erythroblasts of the red bone marrow (about 90%), part of this iron (10%) is stored in the composition of ferritin and hemosiderin.

Physiological iron loss occurs in feces. A small portion of iron is lost through sweat and epidermal cells. Total iron loss is 1 mg/day. Physiological is also considered iron loss with menstrual blood and breast milk.

Iron deficiency occurs when its losses exceed 2 mg/day. With iron deficiency, the most common anemia develops - iron deficiency, i.e. anemia due to an absolute decrease in iron resources in the body.

Red blood cell antigens and blood groups

As part of glycoproteins and glycolipids on the surface of erythrocytes, there are hundreds of antigenic determinants, or antigens (Ags), many of which determine group affiliation blood (blood groups). These Ags could potentially interact with their corresponding antibodies (Abs), if such Abs were contained in the blood serum. However, such an interaction does not occur in the blood of a particular person, since the immune system has already removed the clones of plasma cells secreting these ATs (see Chapter 29 for more details). However, if

the corresponding antibodies enter the blood (for example, during transfusion of someone else’s blood or its components), an interaction reaction between erythrocyte Ags and serum antibodies develops, with often catastrophic consequences (blood type incompatibility). In particular, agglutination (gluing) of red blood cells and their subsequent hemolysis occurs. It is for these reasons that it is so important to determine the group affiliation of the transfused blood (donor blood) and the blood of the person to whom the blood is transfused (recipient), as well as strict compliance with all rules and procedures for transfusion of blood or its components (in the Russian Federation, the procedure for blood transfusion is regulated by order of the Ministry of Health of the Russian Federation and instructions for the use of blood components attached to the order).

Of the hundreds of erythrocyte Ags, the International Society of Blood Transfusion (ISBT) classified the following in alphabetical order as ABO as blood group systems [in the English-language literature the name ABO (the letter “O” is accepted), in the Russian-language literature - AB0 (digit “0”)]. In the practice of blood transfusion (hemotransfusion) and its components, it is mandatory to check for compatibility with the Ag systems A0 (four groups) and Rh (two groups), for a total of eight groups. The remaining systems (they are known as rare) cause blood group incompatibility much less frequently, but they should also be taken into account when carrying out blood transfusions and determining the likelihood of development hemolytic disease in a newborn (see below “Rh-system”).

AB0-SYSTEM

Erythrocyte Ag AB0 systems: A, B and 0 - belong to the class of glycophorins. Their polysaccharide chains contain Ag determinants - agglutinogens A and B. The formation of agglutinogens A and B occurs under the influence of glycosyltransferases encoded by alleles of the gene AB0. This gene encodes three polypeptides (A, B, 0), two of them (glycosyltransferases A and B) modify the polysaccharide chains of glycophorins; polypeptide 0 is functionally inactive. As a result, the surface of red blood cells different persons may contain either agglutinogen A, or agglutinogen B, or both agglutinogens (A and B), or contain neither agglutinogen A nor agglutinogen B. In accordance with the type of expression of agglutinogens A and B on the surface of erythrocytes

In the AB0 system, there are four blood groups, designated by Roman numerals I, II, III and IV. Erythrocytes of blood group I do not contain either agglutinogen A or agglutinogen B, its abbreviated name is 0(I). Red blood cells of blood group IV contain both agglutinogens - AB(IV), group II - A(II), group III - B(III). The first three blood groups were discovered in 1900 by Karl Landsteiner, and the fourth group a little later by Decastrello and Sturli.

Agglutinins.Blood plasma may contain antibodies to agglutinogens A and B (α- and β-agglutinins, respectively). Blood plasma of group 0(I) contains α- and β-agglutinins; group A(II) - β-agglutinins, B(III) - α-agglutinins, blood plasma of group AB(IV) does not contain agglutinins.

Table 24-1.Content in blood different groups(AB0 system) agglutinogens (Ag) and agglutinins (AT)

Thus, in the blood of a particular person, antibodies to erythrocyte Ags of the AB0 system are not simultaneously present (Table 24-1), but when blood is transfused from a donor with one group to a recipient with another group, a situation may arise when both are present in the recipient’s blood at the same time. Ag, and AT is precisely for this Ag, i.e. a situation of incompatibility will arise. In addition, such incompatibility may occur in other blood group systems. That is why it has become a rule that Only blood of the same type can be transfused. More precisely, it is not whole blood that is transfused, but components, since “the indications for transfusion of whole canned blood are donated blood no, except in acute cases massive blood loss when there are no blood substitutes or fresh frozen plasma, red blood cells or their suspension” (from the order of the Ministry of Health of the Russian Federation). And that is why the theoretical idea of ​​“ universal donor» with blood group 0(I) is left in practice.

Rh-SYSTEM

Each person can be Rh-positive or Rh-negative, which is determined by his genotype and the expressed Ags of the Rh system.

Φ Antigens. Six alleles of three genes of the Rh system encode Ags: c, C, d, D, e, E. Taking into account the extremely rare Ags of the Rh system, 47 phenotypes of this system are possible. Φ Antibodies Rh systems belong to IgG class(ATs only to Ag d were not detected). Rh positive And Rh negative individuals. If the genotype of a particular person encodes at least one of Ags C, D and E, such persons Rh positive(in practice, individuals who have Ag D, a strong immunogen, on the surface of their red blood cells are considered Rh positive). Thus, AT are formed not only against “strong” Ag D, but can also be formed against “weak” Ag c, C, e and E. Rh negative only individuals with the cde/cde (rr) phenotype.

Φ Rhesus conflict(incompatibility) occurs during transfusion Rh positive blood donor to an Rh-negative recipient or in the fetus during a second pregnancy of an Rh-negative mother with an Rh-positive fetus (first pregnancy and/or birth of an Rh-positive fetus). In this case, hemolytic disease of the newborn develops.

Leukocytes

Leukocytes are spherical nuclear cells (see Fig. 24-1). There are granules in the cytoplasm of leukocytes. Depending on the type of granules, leukocytes are divided into granulocytes (granular) and agranulocytes (non-granular).

Φ Granulocytes(neutrophils, eosinophils, basophils) contain specific (secondary) and azurophilic (lysosomes) granules.

Φ Agranulocytes(monocytes, lymphocytes) contain only

azurophilic granules. Φ Core. Granulocytes have a lobulated nucleus of varied

forms, hence their common name - polymorphonuclear

leukocytes.Lymphocytes and monocytes have non-lobed

the core is mononuclear leukocytes.

Physiological leukocytosis - a condition characterized by an increase in the number of leukocytes per unit volume of blood above normal (>9x10 9 /l). Among physiological leukocytosis There are functional and protective-adaptive ones.

Φ Functional leukocytosis due to the fact that the body performs certain functions (for example, leukocytosis during pregnancy, an increase in the number of leukocytes in the blood after eating or after prolonged physical work).

Φ Protective-adaptive leukocytosis develops with inflammatory processes, damage to cells and tissues (for example, after heart attacks or strokes, soft tissue injuries), stress reactions.

Leukopenia- a condition in which the number of white blood cells per unit volume of blood decreases below normal (<4х10 9 /л). Различают первичные (врождённые или наследственные) и

secondary (acquired as a result of radiation damage, poisoning, drug use) leukopenia. Leukocyte formula- percentage of certain forms of leukocytes in peripheral blood. Calculation of the leukocyte formula is extremely important for clinical practice, since it is leukocytes that react earlier and faster than other blood elements to external and internal changes (in particular, inflammation).

Relative and absolute changes in the leukocyte formula. When changes relative(percentage) content of one or another type of leukocytes in the leukocyte formula speaks either of relative neutropenia, eosinopenia, lymphopenia, monocytopenia (with a decrease in the percentage of leukocytes of the corresponding type), or about relative neutrophilia, eozonophilia, relative monocytosis, lymphocytosis (with an increase in their relative content).

Changes in absolute leukocyte count per unit volume of blood is denoted as absolute neutropenia, eosinopenia, lymphopenia, monocytopenia (if their absolute number per unit volume of blood decreases) or absolute neutrophilia, eosinophilia, absolute monocytosis or lymphocytosis (if the number of corresponding types of leukocytes increases).

When characterizing changes in the composition of leukocytes, it is necessary to evaluate both relative and absolute (required!) their content. This is determined by the fact that absolute values ​​reflect the true content of certain types of leukocytes in the blood, while relative values ​​characterize only the ratio of different cells to each other in a unit volume of blood.

In many cases, the direction of relative and absolute changes coincides. Often there is, for example, relative and absolute neutrophilia or neutropenia.

The deviation in the relative (percentage) content of cells per unit volume of blood does not always reflect a change in their true, absolute number. Thus, relative neutrophilia can be combined with absolute neutropenia (a similar situation arises if relative neutrophilia is observed in conditions of significant leukopenia: for example, the neutrophil content is 80%, and the total number of leukocytes is only 1.0x10 9 /l).

To determine the absolute number of a particular type of leukocyte in the blood, it is necessary to calculate this value based on the total number of leukocytes and the percentage of corresponding cells(in the example given, 80% of 1.0x10 9 /l will be 0.8x10 9 /l. This is more than two times less than 2.0x10 9 /l - the lower limit of the normal absolute neutrophil content).

Age-related changes in blood cells

Red blood cells. At birth and in the first hours of life, the number of red blood cells in the blood is increased and amounts to 6.0-7.0x10 12 / l. In newborns, anisocytosis with a predominance of macrocytes, as well as an increased content of reticulocytes, is observed. During the first day of the postnatal period, the number of red blood cells decreases, by the 10-14th day it reaches the adult level and continues to decline. The minimum indicator is observed in the 3-6th month of life (physiological anemia), when the level of erythropoietin is reduced. This is due to a decrease in the synthesis of erythropoietin in the liver and the beginning of its production in the kidney. At the 3-4th year of life, the number of red blood cells is reduced (lower than in an adult), i.e. 1 liter contains less than 4.5x10 12. The content of red blood cells reaches the adult norm during puberty.

Leukocytes. The number of leukocytes in newborns is increased and equals 10-30x10 9 /l. The number of neutrophils is 60.5%, eosinophils - 2%, basophils - 0.2%, monocytes - 1.8%, lymphocytes - 24%. During the first 2 weeks, the number of leukocytes decreases to 9-15x10 9 /l, by 4 years it decreases to 7-13x10 9 /l, and by 14 years it reaches the level characteristic of an adult. The ratio of neutrophils and lymphocytes changes, which causes the occurrence of so-called physiological crossovers.

Φ First cross. In a newborn, the ratio of the content of these cells is the same as in an adult. Subsequently, the content of neutrophils decreases, and lymphocytes increase, so that on the 3-4th day their number equalizes. Subsequently, the number of neutrophils continues to decrease and reaches 25% by 1-2 years. At the same age, the number of lymphocytes is 65%.

Φ Second cross. Over the following years, the number of neutrophils gradually increases, and lymphocytes decrease, so that in four-year-old children these indicators are equalized again and constitute 35% of the total number of leukocytes. The number of neutrophils continues to increase, and the number of lymphocytes continues to decrease, and by the age of 14 these indicators correspond to those of an adult.

Lifespan of leukocytes

Granulocytes live in circulating blood for 4-5 hours, and in tissues for 4-5 days. In cases of serious tissue infection, the lifespan of granulocytes is shortened to several hours, since they very quickly enter the site of infection, perform their functions and are destroyed.

Monocytes after 10-12 hours in the bloodstream they enter the tissues. Once in the tissue, they increase in size and become tissue macrophages. In this form, they can live for months until they are destroyed, performing the function of phagocytosis.

Lymphocytes enter the circulatory system constantly in the process of draining lymph from the lymph nodes. A few hours later, they return to the tissues through diapedesis and then return again and again with lymph into the blood. This ensures constant circulation of lymphocytes through the tissue. The lifespan of lymphocytes is months and even years, depending on the body's needs for these cells.

Microphages and macrophages. The main function of neutrophils and monocytes is phagocytosis and subsequent intracellular destruction of bacteria, viruses, damaged cells that have completed their life cycle, and foreign agents. Neutrophils (and to some extent eosinophils) are mature cells that phagocytose various materials (another name for phagocytic neutrophils is microphages). Blood monocytes are immature cells. Only after entering tissues do monocytes mature into tissue macrophages and acquire the ability to fight pathogens. Neutrophils and macrophages move through tissues through amoeboid movements stimulated by substances that are formed in the inflamed area. This attraction of neutrophils and macrophages to the area of ​​inflammation is called chemotaxis.

Neutrophils

Neutrophils are the most numerous type of leukocytes. They make up 40-75% of the total number of leukocytes. The size of a neutrophil in a blood smear is 12 microns; the diameter of a neutrophil migrating in tissues increases to almost 20 microns. Neutrophils are formed in the bone marrow within 7 days, after 4 days they enter the bloodstream and remain in it for 8-12 hours. Life expectancy is about 8 days. Old cells are phagocytosed by macrophages.

Neutrophil pools. There are three pools of neutrophils: circulating, border and reserve.

Φ Circulating- passively transported blood cells. When a bacterial infection of the body occurs, their number increases several (up to 10) times within 24-48 hours due to the border pool, as well as due to the accelerated release of reserve cells from the bone marrow.

Φ Border the pool consists of neutrophils associated with endothelial cells of small vessels of many organs, especially the lungs and spleen. The circulating and boundary pools are in dynamic equilibrium.

Φ Spare pool - mature bone marrow neutrophils.

Core. Depending on the degree of differentiation, they distinguish rod and segmented(see Fig. 24-1, B) neutrophils. In neutrophils in women, one of the nuclear segments contains a drumstick-shaped outgrowth - Barr's body or sex chromatin (this inactivated X chromosome is visible in 3% of neutrophils in a woman's blood smear).

♦ Band neutrophils- immature forms of cells with a horseshoe-shaped nucleus. Normally, their number is 3-6% of the total number of leukocytes.

♦ Segmented neutrophils- mature cells with a nucleus, which consists of 3-5 segments connected by thin bridges.

Φ Nuclear shifts of the leukocyte formula. Since during microscopy of a blood smear the main criterion for identifying different forms of maturity of granular leukocytes is the nature of the nucleus (shape, size, color intensity), shifts in the leukocyte formula are designated as “nuclear”.

Φ Shift left characterized by an increase in the number of young and immature forms of neutrophils (see Fig. 24-4). In acute purulent-inflammatory diseases, in addition to leukocytosis, the content of young forms of neutrophils, usually band neutrophils, less often young neutrophils (metamyelocytes and myelocytes), increases, which indicates a serious inflammatory process.

Φ Shift right manifested by an increased number of segmented nuclear forms of neutrophils.

Φ Nuclear shift index reflects the ratio of the percentage of the sum of all young forms of neutrophils (bands, metamyelocytes, myelocytes, promyelocytes, see Fig. 24-4) to their mature forms. In healthy adults, the nuclear shift index ranges from 0.05 to 0.10. An increase in it indicates a nuclear shift of neutrophils to the left, a decrease indicates a shift to the right.

Neutrophil granules

Φ Azurophilic granules neutrophils contain various proteins that destroy components of the extracellular matrix and have antibacterial activity. The granules contain cathepsins, elastase, proteinase-3 (myeloblastin), azurocidin, defensins, cationic proteins, lysozyme, arylsulfatase. The main enzyme of azurophilic granules is myeloperoxidase. This protein makes up 2-4% of the neutrophil's mass and catalyzes the formation of hypochlorous acid and other toxic agents that significantly enhance the bactericidal activity of the neutrophil.

Φ Specific granules much smaller, but twice as numerous as azurophiles. The granules contain proteins with bacteriostatic properties: lactoferrin, vitamin B 12-binding proteins. In addition, the granules contain lysozyme, collagenase, alkaline phosphatase, and cationic proteins.

Receptors. Receptors for adhesion molecules, cytokines, colony-stimulating factors, opsonins, chemoattractants, and inflammatory mediators are built into the plasmolemma of neutrophils. Binding of their ligands to these receptors leads to activation of neutrophils (exit from the vascular bed, migration

into the site of inflammation, degranulation of neutrophils, formation of superoxides).

Function of neutrophils. Neutrophils remain in the blood for only a few hours (in transit from the bone marrow to tissues), and their inherent functions are performed outside the vascular bed (exit from the vascular bed occurs as a result of chemotaxis) and only after activation of neutrophils. The main function is phagocytosis of tissue debris and destruction of opsonized microorganisms. Phagocytosis and subsequent digestion of the material occurs in parallel with the formation of arachidonic acid metabolites and respiratory burst. Phagocytosis occurs in several stages. After preliminary specific recognition of the material to be phagocytosed, invagination of the neutrophil membrane around the particle occurs and the formation of a phagosome. Next, as a result of the fusion of the phagosome with lysosomes, a phagolysosome is formed, after which the bacteria are destroyed and the captured material is destroyed. For this, lysozyme, cathepsin, elastase, lactoferrin, defensins, and cationic proteins enter the phagolysosome; myeloperoxidase; superoxide O 2 - and hydroxyl radical OH - formed (along with H 2 O 2) during a respiratory explosion. After a single burst of activity, the neutrophil dies. Such neutrophils constitute the main component of pus (“pus” cells).

Φ Activation. Biologically active compounds of various origins: for example, the contents of platelet granules, arachidonic acid metabolites (lipid mediators), acting on neutrophils, stimulate their activity (many of these substances are at the same time chemoattractants, along the concentration gradient of which neutrophils migrate).

Φ Lipid mediators produce activated neutrophils, as well as basophils and mast cells, eosinophils, monocytes and macrophages, platelets. In an activated cell, arachidonic acid is released from membrane phospholipids, from which prostaglandins, thromboxanes, leukotrienes and a number of other biologically active substances are formed.

Φ Respiratory explosion. During the first seconds after stimulation, neutrophils sharply increase oxygen uptake and quickly consume a significant amount of it. This phenomenon is known as respiratory (oxygen) explosion. In this case, H 2 O 2, superoxide O 2 - and hydroxyl radical OH -, which are toxic to microorganisms, are formed.

Φ Chemotaxis. Neutrophils migrate to the site of infection along a concentration gradient of many chemical factors. Important among them are N-formylmethionyl peptides (for example, the chemoattractant f-Met-Leu-Phe), which are formed during the breakdown of bacterial proteins or mitochondrial proteins during cell damage.

Φ Adhesion. The activated neutrophil attaches to the vascular endothelium. Adhesion to the endothelium is stimulated by many agents: anaphylatoxins, IL-I, thrombin, platelet activating factor PAF, leukotrienes LTC 4 and LTB 4, tumor necrosis factor α, etc.

Φ Migration. After attaching to the endothelium and leaving the vessel, neutrophils increase in size, elongate and become polarized, forming a broad head end (lamellipodia) and a narrowed posterior part. The neutrophil, moving the lamellipodia forward, migrates to the source of the chemoattractant. In this case, the granules move to the head end, their membranes merge with the plasmalemma, and the contents of the granules (including proteases) are released from the cell - degranulation.

Eosinophils

but 8-14 days. Eosinophils on their surface have membrane receptors for the Fc fragments of IgG, IgM and IgE, complement components C1s, C3a, C3b, C4 and C5a, the chemokine eotaxin, and interleukins. The migration of eosinophils in tissues is stimulated by eotaxin, histamine, eosinophil chemotaxis factor ECF, interleukin-5, etc. After performing their functions (after degranulation) or in the absence of activation factors (for example, IL-5), eosinophils die.

Metabolic activity. Like neutrophils, eosinophils synthesize arachidonic acid metabolites (lipid mediators), including leukotriene LTC 4 and platelet activating factor PAF.

Chemotaxis. Activated eosinophils move along a gradient of chemotaxis factors - bacterial products and complement elements. Particularly effective as chemoattractants are substances secreted by basophils and mast cells - histamine and eosinophil chemotaxis factor ECF.

Φ Participation in allergic reactions. The contents of eosinophil granules inactivate histamine and leukotriene LTC 4. Eosinophils produce an inhibitor that blocks mast cell degranulation. Slow reacting factor anaphylaxis (SRS-A), released by basophils and mast cells, is also inhibited by activated eosinophils.

Φ Side effects of eosinophils. Substances secreted by the eosinophil can damage normal tissue. Thus, with a constant high content of eosinophils in the blood, chronic secretion of the contents of eosinophil granules causes thromboembolic damage, tissue necrosis (especially the endocardium) and the formation of fibrous tissue. IgE stimulation of eosinophils can cause reversible changes in vascular permeability. Secretion products of eosinophils damage the bronchial epithelium and activate complement and the blood coagulation system.

Basophils

Basophils make up 0-1% of the total number of leukocytes in circulating blood. Basophils with a diameter of 10-12 microns remain in the blood for 1-2 days. Like other granular leukocytes, they can leave the bloodstream when stimulated, but their ability for amoeboid movement is limited. Lifespan and tissue fate are unknown.

Specific granules quite large (0.5-1.2 microns), colored metachromatically (in a different color than the dye, from

reddish-violet to intense violet). The granules contain various enzymes and mediators. The most significant of them include heparin sulfate (heparin), histamine, inflammatory mediators (for example, slow-reacting anaphylaxis factor SRS-A, eosinophil chemotaxis factor ECF).

Metabolic activity. When activated, basophils produce lipid mediators. Unlike mast cells, they do not have PGD 2 synthetase activity and oxidize arachidonic acid predominantly to leukotriene

LTC 4.

Function. Activated basophils leave the bloodstream and participate in allergic reactions in tissues. Basophils have high-affinity surface receptors for the Fc fragments of IgE, and IgE is synthesized by plasma cells when Ag (allergen) enters the body. Basophil degranulation is mediated by IgE molecules. In this case, cross-linking of two or more IgE molecules occurs. The release of histamine and other vasoactive factors during degranulation and the oxidation of arachidonic acid cause the development of an immediate allergic reaction (such reactions are characteristic of allergic rhinitis, some forms of bronchial asthma, anaphylactic shock).

Monocytes

Monocytes (see Fig. 24-1, E) are the largest leukocytes (diameter in a blood smear is about 15 microns), their number is 2-9% of all leukocytes in circulating blood. They are formed in the bone marrow, enter the bloodstream and circulate for about 2-4 days. Blood monocytes are actually immature cells on their way from the bone marrow to the tissues. In tissues, monocytes differentiate into macrophages; a collection of monocytes and macrophages - mononuclear phagocyte system.

Activation of monocytes. Various substances formed at sites of inflammation and tissue destruction are agents of chemotaxis and activation of monocytes. As a result of activation, cell size increases, metabolism increases, monocytes secrete biologically active substances (IL-1, colony-stimulating factors M-CSF and GM-CSF, Pg, interferons, neutrophil chemotaxis factors, etc.).

Function. The main function of monocytes and macrophages formed from them is phagocytosis. Lysosomal enzymes, as well as intracellularly formed H 2 O 2, OH -, O 2 -, participate in the digestion of phagocytosed material. Activated monocytes/macrophages also produce endogenous pyrogens.

Φ Pyrogens. Monocytes/macrophages produce endogenous pyrogens(IL-1, IL-6, IL-8, tumor necrosis factor TNF-α, α-interferon) - polypeptides that trigger metabolic changes in the thermoregulation center (hypothalamus), which leads to an increase in body temperature. The formation of prostaglandin PGE 2 plays a critical role. The formation of endogenous pyrogens by monocytes/macrophages (as well as a number of other cells) is caused by exogenous pyrogens- proteins of microorganisms, bacterial toxins. The most common exogenous pyrogens are endotoxins (lipopolysaccharides of gram-negative bacteria).

Macrophage- differentiated form of monocytes - large (about 20 microns), mobile cell of the mononuclear phagocyte system. Macrophages- professional phagocytes, they are found in all tissues and organs; it is a mobile population of cells. The lifespan of macrophages is months. Macrophages are divided into resident and mobile. Resident macrophages are normally found in tissues in the absence of inflammation. Among them, there are free, round-shaped, and fixed macrophages - star-shaped cells, attached with their processes to the extracellular matrix or to other cells.

Properties of a macrophage depend on their activity and location. Lysosomes of macrophages contain bactericidal agents: myeloperoxidase, lysozyme, proteinases, acid hydrolases, cationic proteins, lactoferrin, superoxide dismutase - an enzyme that promotes the formation of H 2 O 2, OH -, O 2 -. Under the plasma membrane there are large numbers of actin microfilaments, microtubules, and intermediate filaments necessary for migration and phagocytosis. Macrophages migrate along a concentration gradient of many substances coming from various sources. Activated macrophages

form irregularly shaped cytoplasmic pseudopodia involved in amoeboid movement and phagocytosis. Functions. Macrophages capture denatured proteins and aged red blood cells from the blood (fixed macrophages of the liver, spleen, bone marrow). Macrophages phagocytose cell debris and tissue matrix. Nonspecific phagocytosis characteristic of alveolar macrophages that capture dust particles of various natures, soot, etc. Specific phagocytosis occurs when macrophages interact with an opsonized bacterium. An activated macrophage secretes more than 60 factors. Macrophages exhibit antibacterial activity by releasing lysozyme, acid hydrolases, cationic proteins, lactoferrin, H 2 O 2, OH -, O 2 -. Antitumor activity consists of the direct cytotoxic effect of H 2 O 2, arginase, cytolytic proteinase, tumor necrosis factor from macrophages. A macrophage is an antigen-presenting cell: it processes Ag and presents it to lymphocytes, which leads to stimulation of lymphocytes and the launch of immune reactions (see more in Chapter 29). Interleukin-1 from macrophages activates T-lymphocytes and, to a lesser extent, B-lymphocytes. Macrophages produce lipid mediators: PgE 2 and leukotrienes, platelet activating factor PAF. The cell also secretes α-interferon, which blocks viral replication. An activated macrophage secretes enzymes that destroy the extracellular matrix (elastase, hyaluronidase, collagenase). On the other hand, growth factors synthesized by the macrophage effectively stimulate the proliferation of epithelial cells (transforming growth factor TGFα, bFGF), proliferation and activation of fibroblasts (platelet-derived growth factor PDGF), collagen synthesis by fibroblasts (transforming growth factor TGFp), the formation of new blood vessels - angiogenesis (fibroblast growth factor bFGF). Thus, the main processes underlying wound healing (re-epithelialization, formation of extracellular matrix, restoration of damaged vessels) are mediated by growth factors produced by macrophages. By producing a number of colony-stimulating factors (macrophages - M-CSF, granulocytes - G-CSF), macrophages influence the differentiation of blood cells.

Lymphocytes

Lymphocytes (see Fig. 24-1, E) make up 20-45% of the total number of blood leukocytes. Blood is the medium in which lymphocytes circulate between the organs of the lymphoid system and other tissues. Lymphocytes can exit the vessels into the connective tissue, and also migrate through the basement membrane and penetrate the epithelium (for example, in the intestinal mucosa). The lifespan of lymphocytes ranges from several months to several years. Lymphocytes are immunocompetent cells that are of great importance for the body’s immune defense reactions (see Chapter 29 for more details). From a functional point of view, B-, T-lymphocytes and NK cells are distinguished.

B lymphocytes(pronounced “bae”) are formed in the bone marrow and make up less than 10% of blood lymphocytes. Some B lymphocytes in tissues differentiate into clones of plasma cells. Each clone synthesizes and secretes antibodies against only one Ag. In other words, plasma cells and the antibodies they synthesize provide humoral immunity.

T-lymphocytes. T-lymphocyte precursor cells enter the thymus from the bone marrow. Differentiation of T lymphocytes occurs in the thymus. Mature T lymphocytes leave the thymus and are found in the peripheral blood (80% or more of all lymphocytes) and lymphoid organs. T-lymphocytes, like B-lymphocytes, react (i.e., recognize, multiply and differentiate) to specific Ags, but unlike B-lymphocytes, the participation of T-lymphocytes in immune reactions is associated with the need to recognize the main proteins in the membrane of other cells. MHC histocompatibility complex. The main functions of T-lymphocytes are participation in cellular and humoral immunity (thus, T-lymphocytes destroy abnormal cells of their body, participate in allergic reactions and in the rejection of foreign transplants). Among T-lymphocytes, CD4+- and CD8+-lymphocytes are distinguished. CD4+ lymphocyte I(T-helpers) support the proliferation and differentiation of B lymphocytes and stimulate the formation of cytotoxic T lymphocytes, and also promote the proliferation and differentiation of suppressor T lymphocytes.

NK cells- lymphocytes lacking the surface cell determinants characteristic of T- and B-cells. These cells make up about 5-10% of all circulating lymphocytes, contain cytolytic granules with perforin, and destroy transformed (tumor) and virus-infected cells, as well as foreign cells.

Blood plates

Platelets, or blood platelets (Fig. 24-13), are fragments of megakaryocytes located in the red bone marrow. The size of blood platelets in a blood smear is 3-5 microns. The number of platelets in the circulating blood is 190-405x10 9 /l. Two thirds of the blood platelets are in the blood, the rest are deposited in the spleen. The lifespan of platelets is 8 days. Old platelets are phagocytosed in the spleen, liver and bone marrow. Platelets circulating in the blood can be activated under a number of circumstances; activated platelets participate in blood clotting and restoration of the integrity of the vessel wall. One of the most important properties of activated blood platelets is their ability to mutual adhesion and aggregation, as well as adhesion to the wall of blood vessels.

Glycocalyx. The protruding parts of the molecules that make up the integral proteins of the plasma membrane, rich in polysaccharide side chains (glycoproteins), create the outer covering of the lipid bilayer - the glycocalyx. Coagulation factors and immunoglobulins are also adsorbed here. Receptor sites are located on the outer parts of glycoprotein molecules. After their combination with agonists, an activation signal is induced, transmitted to the internal parts of the peripheral platelet zone.

Plasma membrane contains glycoproteins that act as receptors for platelet adhesion and aggregation. Thus, glycoprotein Ib (GP Ib, Ib-IX) is important for platelet adhesion; it binds to von Willebrand factor and subendothelial connective tissue. Glycoprotein IV (GP IIIb) is a thrombospondin receptor. Glycoprotein IIb-IIIa (GP IIb-IIIa) - receptor for fibrinogen, fibronectin, thrombospondin, vitronectin, von Willebrand factor; these factors promote adhesion and aggregation of thrombosis

Rice. 24-13. The platelet has the shape of an oval or round disk. Small accumulations of glycogen and large granules of several types are visible in the cytoplasm. The peripheral part contains circular bundles of microtubules (necessary for maintaining the oval shape of the platelet), as well as actin, myosin, gelsolin and other contractile proteins necessary for changing the shape of platelets, their mutual adhesion and aggregation, as well as for retraction of the blood clot formed during platelet aggregation . Along the periphery of the platelet there are also anastomosing membrane tubules that open into the extracellular environment and are necessary for the secretion of the contents of α-granules. Scattered in the cytoplasm are narrow, irregularly shaped membrane tubes that make up a dense tubular system. The tubules contain cyclooxygenase (necessary for the oxidation of arachidonic acid and the formation of thromboxane TXA 2. Acetylsalicylic acid (aspirin) irreversibly acetylates cyclooxygenase localized in the tubules of the dense tubular system, which blocks the formation of thromboxane, necessary for platelet aggregation; as a result, platelet function is impaired and bleeding time is prolonged ) .

cytes, mediating the formation of fibrinogen “bridges” between them.

Granules. Platelets contain three types of granules (α-, δ-, λ-) and microperoxisomes.

Φ α-Granules contain various glycoproteins (fibronectin, fibrinogen, von Willebrand factor), heparin binding proteins (eg platelet factor 4), platelet-derived growth factor PDGF and transforming growth factor β, plasma coagulation factors VIII and V, and thrombospondin (promotes platelet adhesion and aggregation) and cell adhesion receptor GMP-140. Φ Other granules.δ-Granules accumulate inorganic phosphate P., ADP, ATP, Ca 2 +, serotonin and histamine (serotonin and histamine are not synthesized in platelets, but come from plasma). λ-Granules contain lysosomal enzymes and may be involved in clot dissolution. Microperoxisomes have peroxidase activity. Functions of platelets. Under physiological conditions, platelets are in an inactive state, i.e. circulate freely in the blood, do not adhere to each other and are not attached to the endothelium of the vessel (this is partly due to the fact that endothelial cells produce prostacyclin PGI 2, which prevents platelet adhesion to the vessel wall). However, when a blood vessel is damaged, platelets, together with plasma clotting factors, form a blood clot - a thrombus, which prevents bleeding.

Stop bleeding occurs in three stages. 1. First, the lumen of the blood vessel contracts. 2. Next, in the damaged area of ​​the vessel, platelets attach to the vessel wall and, layering on top of each other, form a platelet hemostatic plug (white thrombus). These processes (changes in the shape of blood platelets, their adhesion and aggregation) are reversible, so that weakly aggregated platelets can be separated from hemostatic platelet plugs and returned to the bloodstream. 3. Finally, soluble fibrinogen is converted into insoluble fibrin, which forms a strong three-dimensional network, in the loops of which blood cells, including red blood cells, are located. Is it fibrin, or red, thrombus.

Φ The formation of a fibrin thrombus is preceded by a cascade of proteolytic reactions, leading to the activation of the enzyme thrombin, which converts fibrinogen into fibrin. Thus, at one of the stages of thrombus formation, blood clotting (hemocoagulation) occurs - part of the hemostasis system, to which platelets are most directly related.

Hemostasis

In the applied sense, the term “hemostasis” (from gr. haima- blood, stasis- stop) is used to denote the actual process of stopping bleeding. The hemostatic system includes factors and mechanisms of three categories: coagulation, anticoagulation and fibrinolytic.

Φ Coagulation system namely, plasma coagulation factors (procoagulants), forming a complex hemocoagulation cascade, ensures fibrinogen coagulation and thrombus formation (Fig. 24-14). The cascade of reactions leading to the formation of thrombin can occur in two ways - external (in the figure on the left and above) and internal (in the figure on the right and above). To initiate reactions of the extrinsic pathway, the appearance of tissue factor on the outer surface of the plasma membrane of platelets, monocytes and endothelium is necessary. The intrinsic pathway begins with the activation of factor XII upon its contact with the damaged endothelial surface. The concept of internal and external coagulation pathways is very arbitrary, since the cascade of blood coagulation reactions occurs primarily along the external route, and not along two relatively independent pathways.

Φ Anticoagulant system physiological anticoagulants cause inhibition or blockade of blood coagulation.

Φ Fibrinolytic system carries out lysis of fibrin thrombus.

Plasma coagulation factors - various plasma components responsible for the formation of a blood clot. Coagulation factors are designated by Roman numerals (a lowercase letter “a” is added to the number of the activated form of the factor).

Rice. 24-14. Hemocoagulation cascade . Activation of factor XII triggers the internal (contact) mechanism, the release of tissue factor, and activation of factor VII triggers the external coagulation mechanism. Both pathways lead to the activation of factor X. In rectangles with rounded corners are the numbers of plasma coagulation factors. Enzyme complexes are adjacent rectangles with solid and intermittent boundaries.

♦ I- soluble fibrinogen, which is converted into insoluble fibrin under the influence of thrombin (factor Ha).

♦ II- prothrombin (proenzyme), converted into thrombin protease (factor IIa) under the influence of the factor Xa complex, phospholipids of platelet and other cell membranes, Ca 2 + and factor Va.

♦ III- tissue factor. Complex of tissue factor, phospholipids, factor VIIa and Ca 2+ triggers the external coagulation mechanism.

♦ IV- Ca 2+.

♦ V- proaccelerin is a precursor of accelerin (Va), an activator protein of the Xa-Va-Ca 2+ membrane complex.

♦ VII- proconvertin (proenzyme), VIIa - protease that activates factors X and IX.

♦ VIII- inactive antihemophilic globulin A - a precursor of factor VIIIa (active antihemophilic globulin) - an activator protein of the membrane complex IXa-VIIIa-Ca 2+. Factor VIII deficiency causes the development of classical hemophilia A, which is observed only in men.

♦ IX- inactive antihemophilic globulin B (proenzyme, inactive Christmas factor) - a precursor of active antihemophilic factor B (active Christmas factor) - a protease that activates factor X. Factor IX deficiency leads to the development of hemophilia B (Christmas disease).

♦ X- inactive Stewart-Prower factor (active form - factor Xa - protease that activates factor II), deficiency of Stewart factor leads to coagulation defects.

♦ XI- proenzyme of the contact pathway of blood coagulation - an inactive plasma precursor of thromboplastin (the active form is factor XIa - a serine protease that converts factor IX into factor IXa). Factor XI deficiency causes bleeding.

♦ XII- inactive Hageman factor - proenzyme of the contact pathway of blood coagulation, active form - factor XIIa (active Hageman factor) - activates factor XI, prekallikrein (proenzyme of the contact pathway of blood coagulation), plasminogen.

♦ XIII- fibrin-stabilizing factor (Lucky-Laurent factor) - thrombin-activated factor XIII (factor XIIIa), forms insoluble fibrin, catalyzing the formation of amide bonds between fibrin monomer molecules, fibrin and fibronectin.

External path plays a central role in blood clotting. Enzyme membrane complexes (see below) are formed only in the presence of platelets, tissue factor endothelial cells and negatively charged phospholipids on the outer surface of the plasma membrane, i.e. during the formation of negatively charged (thrombogenic) areas and exposure to tissue factor apoprotein. In this case, tissue factor and the surface of the cell membrane become accessible to plasma factors. F Enzyme activation. Circulating blood contains proenzymes (factors II, VII, IX, X). Cofactor proteins (factors Va, VIIIa, as well as tissue factor - factor III) contribute to the conversion of proenzymes into enzymes (serine proteases). F Enzyme membrane complexes. When the cascade mechanism of enzyme activation is activated, three enzyme complexes associated with phospholipids of the cell membrane are sequentially formed. Each complex consists of a proteolytic enzyme, a cofactor protein and Ca 2+ ions: VIIa-tissue factor-phospholipid-Ca 2+, Ka-VIIIa-phospholipid-Ca2+ (tenase complex, factor X activator); Xa-Va-phospholipid-Ca 2+ (prothrombinase complex, prothrombin activator). The cascade of enzymatic reactions ends with the formation of fibrin monomers and the subsequent formation of a blood clot. F Ca 2+ ions. The interaction of enzyme complexes with cell membranes occurs with the participation of Ca 2 + ions. The γ-carboxyglutamic acid residues in factors \VIIIa, Ka, Xa and prothrombin ensure the interaction of these factors through Ca 2 + with negatively charged phospholipids of cell membranes. Without Ca 2+ ions, blood does not clot. That is why, in order to prevent blood clotting, the Ca 2 + concentration is reduced by deionization of calcium citrate (citrate blood) or precipitation of calcium in the form of oxalates (oxalate blood). F Vitamin K Carboxylation of glutamic acid residues in the proenzymes of the procoagulant pathway is catalyzed by carboxylase, the coenzyme of which is the reduced form of vitamin K (naphthoquinone). That's why

Vitamin K deficiency inhibits blood clotting and is accompanied by bleeding, subcutaneous and internal hemorrhages, and structural analogues of vitamin K (for example, warfarin) are used in clinical practice to prevent thrombosis.

Contact path Blood coagulation begins with the interaction of the proenzyme (factor XII) with the damaged endothelial surface of the vascular wall. This interaction leads to the activation of factor XII and initiates the formation of membrane enzyme complexes of the contact phase of coagulation. These complexes contain the enzymes kallikrein, factors XIa (plasma precursor of thromboplastin) and XIIa (Hageman factor), as well as a cofactor protein - high molecular weight kininogen.

Anticoagulant blood system. Physiological inhibitors play an important role in maintaining blood in a liquid state and preventing the spread of a blood clot beyond the damaged area of ​​the vessel. Thrombin, which is formed as a result of blood coagulation reactions and ensures the formation of a blood clot, is washed out of the blood clot by the blood flow; Thrombin is subsequently inactivated when interacting with inhibitors of blood clotting enzymes and at the same time activates the anticoagulant phase, which inhibits the formation of a blood clot.

F Anticoagulant phase. This phase is triggered by thrombin (factor II), causing the formation of enzyme complexes of the anticoagulant phase on the intact vascular endothelium. In addition to thrombin, the reactions of the anticoagulant phase involve endothelial cell thrombomodulin, vitamin K-dependent serine protease - protein C, activating protein S and plasma coagulation factors Va and

VIIIa.

F Physiological inhibitors blood clotting enzymes (antithrombin III, heparin, a 2-macroglobulin, anticonvertin, a j -antitrypsin) limit the spread of a blood clot to the site of vessel damage.

Fibrinolytic system. The clot may dissolve within a few days after formation. With fibrinolysis - enzymatic breakdown of fibrin fibers -

Soluble peptides are produced. Fibrinolysis occurs under the action of the serine protease plasmin, more precisely, through the interaction of fibrin, plasminogen and tissue plasminogen activator.

Laboratory parameters of the hemostasis system. Blood of a healthy person in vitro coagulates in 5-10 minutes. In this case, the formation of the prothrombinase complex takes 5-8 minutes, the activation of prothrombin - 2-5 s, and the conversion of fibrinogen to fibrin - 2-5 s. In clinical practice, to assess hemostasis, the content of various components of the coagulation system, anticoagulants and fibrinolysis are assessed. The simplest laboratory methods include determining bleeding time, thrombin and prothrombin time, activated partial thromboplastin time and prothrombin index.

Chapter Summary

Blood is a liquid connective tissue circulating in the vascular system, which has the most important functions: transport, immune, blood clotting and maintaining homeostasis of the body.

The average adult contains approximately 5 liters of whole blood, which contains about 45% formed elements, suspended in 55% plasma and solutions.

Plasma contains proteins (albumin, globulins, fibrinogen, enzymes, hormones, etc.), lipids (cholesterol, triglycerides) and carbohydrates (glucose).

Red blood cells are anucleate disc-like cells that deliver oxygen to all cells of the body through hemoglobin.

Changes in the number of red blood cells, their shape, size, color and maturity are a valuable indicator for the diagnosis of various diseases.

At the end of the 4th month of life, old red blood cells are absorbed by macrophages. Their hemoglobin, including iron, is processed into a diagnostically important substance - bilirubin.

Leukocytes are morphologically divided into granulocytes (eosinophils, basophils and neutrophils) and agranulocytes (monocytes and lymphocytes). Lymphocytes are functionally divided into T and B cells with different subsets.

Leukocytes protect the body from infection using phagocytosis and various antimicrobial agents, releasing mediators that control inflammation and thereby promoting healing.

Hematopoiesis is the development of blood cells from neutral multipotent stem cells of the bone marrow. Immature cells differentiate into mature cells under the influence of hematopoietins and other cytokines.

Platelets (blood platelets) are small, irregularly shaped, nuclear-free structures that, together with plasma proteins, control blood clotting.

During blood transfusion, the donor and recipient must avoid agglutination between the red blood cell-associated antigens A, B and Rh and the anti-A, anti-B and anti-Rh antibodies found in the plasma.

Donation is presented in society as a noble and useful act. Individuals who regularly donate blood receive various benefits from its components. These include additional days off and free food vouchers.

But is plasma donation safe? And what is the other side of the coin? What should you know about the collection procedure and how to properly prepare for medical manipulation?

Plasma. A little educational program

Plasma is the liquid fraction of blood. Its specific gravity is 60% of the mass of whole blood. The task of this fluid is to transport blood cells to various organs and tissues, deliver nutrients and remove waste products.

Plasma is necessary to maintain the functioning of the homeostasis system and the formation of fibrin clots at the site of injury. The composition of this biological fluid includes protein fractions that ensure the salt balance of the body. In addition, they participate in metabolic processes and stabilize the functioning of the immune system.

Plasma is widely used in medical practice. The administration of this blood component is indicated for patients in shock, massive blood loss, overdose of anticoagulants, and cardiomyopathies of various etiologies.

All these conditions are considered extremely severe. Therefore, by donating blood components, a donor saves someone's life.

Blood plasma donation. Benefit for the donor

The collection procedure is an invasive procedure. Therefore, there are cases of deliberate distortion of information about the benefits of donating blood plasma for a donor.

The World Health Organization has developed recommendations for donating blood and its components, including the frequency and volume of biological fluid collection. Following WHO protocols is mandatory for staff of medical institutions.

Benefits of donating blood plasma for a donor:

1. Updating the components of biological fluid.

2. Prevention of atherosclerosis, ischemia, and embolism.

3. Reducing cholesterol levels, which reduces the risk of heart attack and cerebrovascular accidents.

4. Maintaining a healthy lifestyle - the requirements for a potential donor are quite strict.

5. Prevention of diseases of the liver, urinary system, pancreas.

6. Increased life span - it has been proven that donors live on average 5 years longer than their peers.

7. For women - prevention of breakthrough uterine bleeding, difficult childbirth with massive blood loss.

8. Prevention of bleeding - donation is a kind of training for the homeostasis system. In addition, the body learns to quickly restore lost biological fluid.

9. Material side – donation of biological fluid components is not always free of charge. The donor receives additional time off, which can be added to the main vacation. The “honorary donor” status is a list of various benefits provided by the state.

10. Moral satisfaction - the very fact that plasma donation can save the life of another person;

11. Before donation, a mandatory medical examination is carried out. And even if the donor’s candidacy is rejected, he will know that he needs to undergo examination and quality treatment from a specialized specialist. This will be beneficial even without donating blood plasma.

It is possible to donate biological raw materials only in specialized medical institutions. If WHO protocols are strictly followed, the benefits of donating blood plasma are undeniable.

Blood plasma donation. Harm to the donor

Any medical manipulation both treats and injures tissues and systems of the body. When donating blood plasma, harm to the donor can occur in the following cases:

The procedure is carried out without preliminary examination;

Manipulations are carried out with a reusable instrument;

Infection of the donor due to violation of asepsis rules;

Collection of excess volume of biological fluid;

Blood components are a valuable biological substance. Therefore, transfusion specialists strictly adhere to the protocols of the World Health Organization.

During the year, 10 acts of plasma donation are allowed for 1 donor and no more than 600 ml of biological fluid per manipulation. Medical institutions maintain strict records. Therefore, it will not be possible to exceed the frequency of donations.

When donating blood plasma, harm can be caused not by the fact of blood loss itself, but by violation of rules and safety precautions during the procedure for collecting biological fluid.

How does donation work?

Donation means strictly following the rules of preparation for the procedure and maintaining a healthy lifestyle. Just the desire to donate biological fluid is not enough.

Requirements for a potential donor:

1. Age from 18 to 60 years and weight at least 50 kg. In rare cases, the minimum body weight is 47 kg.

2. Be a citizen or have a residence permit. You must have identification documents with you.

3. Be healthy.

4. Plasma is not collected from women during menstruation.

Before collecting biological fluid, a potential donor is examined by a doctor. A general blood test is performed, the group and Rh factor are determined, and tested for syphilis, hepatitis and HIV. If the hemoglobin level is reduced, plasma collection is not performed.

If the candidate is allowed to undergo donation, he must have a snack before undergoing medical procedures. Usually it's tea with a bun.

The patient should be in a supine position. During the procedure, the donor uses 2 hands. Biological fluid is collected from one. The blood enters a centrifuge to separate red blood cells, platelets, and other cells from the plasma.

Then the platelet and erythrocyte mass obtained after centrifugation is injected into the vein of the second arm. The resulting plasma is frozen.

Behavior after donation

During plasma collection, the amount of hemoglobin does not decrease, as when donating whole blood. But the body still experiences stress, so weakness and dizziness are possible after donation.

How to behave so that donating blood plasma brings benefits and not harm:

1. Don't smoke.

2. Forget about alcoholic drinks for a day. You should not believe the myth about the benefits of red wine for recovery after blood loss.

3. After collecting plasma, do not remove the pressure bandage for several hours.

4. Rest for half an hour after the manipulation. Eat a bun, drink tea.

5. You should not go to the gym or engage in labor feats during the day.

6. Eat normally and drink enough water for 2 days after donation.

Failure to follow the rules of behavior after donating blood plasma will harm the donor, since the body will recover much more slowly. There will be weakness and dizziness.

Before deciding to donate blood components, discuss the benefits of donating blood plasma with a transfusiologist. Well, the harm of this medical manipulation is extremely doubtful.

Blood, continuously circulating in a closed system of blood vessels, performs the most important functions in the body: transport, respiratory, regulatory and protective. It ensures relative constancy of the internal environment of the body.

Blood is a type of connective tissue consisting of a liquid intercellular substance of complex composition - plasma and cells suspended in it - blood cells: erythrocytes (red blood cells), leukocytes (white blood cells) and platelets (blood platelets). 1 mm 3 of blood contains 4.5–5 million erythrocytes, 5–8 thousand leukocytes, 200–400 thousand platelets.

In the human body, the amount of blood is on average 4.5–5 liters or 1/13 of his body weight. Blood plasma by volume is 55–60%, and formed elements 40–45%. Blood plasma is a yellowish translucent liquid. It consists of water (90–92%), mineral and organic substances (8–10%), 7% proteins. 0.7% fat, 0.1% glucose, the rest of the dense remainder of plasma - hormones, vitamins, amino acids, metabolic products.

Formed elements of blood

Erythrocytes are anucleate red blood cells that have the shape of biconcave discs. This shape increases the cell surface by 1.5 times. The cytoplasm of red blood cells contains the protein hemoglobin - a complex organic compound consisting of the protein globin and the blood pigment heme, which includes iron.

The main function of red blood cells is to transport oxygen and carbon dioxide. Red blood cells develop from nucleated cells in the red bone marrow of cancellous bone. During the process of maturation, they lose their nucleus and enter the blood. 1 mm 3 of blood contains from 4 to 5 million red blood cells.

The lifespan of red blood cells is 120–130 days, then they are destroyed in the liver and spleen, and bile pigment is formed from hemoglobin.

Leukocytes are white blood cells that contain nuclei and do not have a permanent shape. 1 mm 3 of human blood contains 6–8 thousand of them.

Leukocytes are formed in the red bone marrow, spleen, lymph nodes; Their lifespan is 2–4 days. They are also destroyed in the spleen.

The main function of leukocytes is to protect organisms from bacteria, foreign proteins, and foreign bodies. Making amoeboid movements, leukocytes penetrate through the walls of capillaries into the intercellular space. They are sensitive to the chemical composition of substances secreted by microbes or decayed cells of the body, and move towards these substances or decayed cells. Having come into contact with them, leukocytes envelop them with their pseudopods and pull them inside the cell, where they are broken down with the participation of enzymes.

Leukocytes are capable of intracellular digestion. In the process of interaction with foreign bodies, many cells die. At the same time, decay products accumulate around the foreign body, and pus is formed. I. I. Mechnikov called leukocytes that capture various microorganisms and digest them phagocytes, and the phenomenon of absorption and digestion itself was called phagocytosis (absorbing). Phagocytosis is a protective reaction of the body.

Platelets (blood platelets) are colorless, nuclear-free, round-shaped cells that play an important role in blood clotting. There are from 180 to 400 thousand platelets in 1 liter of blood. They are easily destroyed when blood vessels are damaged. Platelets are produced in red bone marrow.

Blood cells, in addition to the above, play a very important role in the human body: during blood transfusion, coagulation, as well as in the production of antibodies and phagocytosis.

Blood transfusion

For some illnesses or blood loss, a person is given a blood transfusion. A large loss of blood disrupts the constancy of the internal environment of the body, blood pressure drops, and the amount of hemoglobin decreases. In such cases, blood taken from a healthy person is injected into the body.

Blood transfusions have been used since ancient times, but often resulted in death. This is explained by the fact that donor red blood cells (that is, red blood cells taken from a person donating blood) can stick together into lumps that close small vessels and impair blood circulation.

The gluing of red blood cells - agglutination - occurs if the donor's red blood cells contain a gluing substance - agglutinogen, and the blood plasma of the recipient (the person to whom blood is transfused) contains the gluing substance agglutinin. Different people have certain agglutinins and agglutinogens in their blood, and in connection with this, the blood of all people is divided into 4 main groups according to their compatibility

The study of blood groups made it possible to develop rules for blood transfusion. Persons giving blood are called donors, and persons receiving it are called recipients. When giving blood transfusions, blood group compatibility is strictly observed.

Any recipient can be injected with blood of group I, since its red blood cells do not contain agglutinogens and do not stick together, therefore persons with blood group I are called universal donors, but they themselves can only be injected with blood of group I.

The blood of people of group II can be transfused to persons with blood groups II and IV, blood of group III - to persons of III and IV. Blood from a group IV donor can be transfused only to persons of this group, but they themselves can be transfused with blood from all four groups. People with blood group IV are called universal recipients.

Blood transfusions treat anemia. It can be caused by the influence of various negative factors, as a result of which the number of red blood cells in the blood decreases, or the content of hemoglobin in them decreases. Anemia also occurs with large blood losses, with insufficient nutrition, dysfunction of the red bone marrow, etc. Anemia is curable: increased nutrition and fresh air help restore the normal level of hemoglobin in the blood.

The blood clotting process is carried out with the participation of the protein prothrombin, which converts the soluble protein fibrinogen into insoluble fibrin, which forms a clot. Under normal conditions, there is no active enzyme thrombin in the blood vessels, so the blood remains liquid and does not clot, but there is an inactive enzyme prothrombin, which is formed with the participation of vitamin K in the liver and bone marrow. The inactive enzyme is activated in the presence of calcium salts and is converted into thrombin by the action of the enzyme thromboplastin, secreted by red blood cells - platelets.

When a cut or injection occurs, the platelet membranes are broken, thromboplastin passes into the plasma and the blood clots. The formation of a blood clot in places of vascular damage is a protective reaction of the body, protecting it from blood loss. People whose blood is unable to clot suffer from a serious disease - hemophilia.

Immunity

Immunity is the body's immunity to infectious and non-infectious agents and substances with antigenic properties. In addition to phagocyte cells, chemical compounds - antibodies (special proteins that neutralize antigens - foreign cells, proteins and poisons) also take part in the immune reaction of immunity. In blood plasma, antibodies glue foreign proteins together or break them down.

Antibodies that neutralize microbial poisons (toxins) are called antitoxins. All antibodies are specific: they are active only against certain microbes or their toxins. If a person’s body has specific antibodies, it becomes immune to these infectious diseases.

The discoveries and ideas of I. I. Mechnikov about phagocytosis and the significant role of leukocytes in this process (in 1863 he gave his famous speech on the healing powers of the body, in which the phagocytic theory of immunity was first outlined) formed the basis of the modern doctrine of immunity (from the Latin . "immunis" - liberated). These discoveries have made it possible to achieve great success in the fight against infectious diseases, which for centuries have been the true scourge of humanity.

The role of protective and therapeutic vaccinations in the prevention of infectious diseases is great - immunization with vaccines and serums that create artificial active or passive immunity in the body.

There are innate (species) and acquired (individual) types of immunity.

Innate immunity is a hereditary trait and ensures immunity to a particular infectious disease from the moment of birth and is inherited from parents. Moreover, immune bodies can penetrate through the placenta from the vessels of the mother’s body into the vessels of the embryo, or newborns receive them with mother’s milk.

Acquired immunity are divided into natural and artificial, and each of them is divided into active and passive.

Natural active immunity produced in humans during the course of an infectious disease. Thus, people who had measles or whooping cough in childhood no longer get sick with them again, since protective substances - antibodies - have formed in their blood.

Natural passive immunity is caused by the transition of protective antibodies from the blood of the mother, in whose body they are formed, through the placenta into the blood of the fetus. Passively and through mother's milk, children receive immunity to measles, scarlet fever, diphtheria, etc. After 1–2 years, when the antibodies received from the mother are destroyed or partially removed from the child's body, his susceptibility to these infections increases sharply.

Artificial active immunity occurs after vaccination of healthy people and animals with killed or weakened pathogenic poisons - toxins. The introduction of these drugs - vaccines - into the body causes a mild form of the disease and activates the body's defenses, causing the formation of appropriate antibodies in it.

To this end, the country is systematically vaccinating children against measles, whooping cough, diphtheria, polio, tuberculosis, tetanus and others, due to which a significant reduction in the number of diseases of these serious diseases has been achieved.

Artificial passive immunity is created by injecting a person with serum (blood plasma without the fibrin protein) containing antibodies and antitoxins against microbes and their poisonous toxins. Serums are obtained mainly from horses, which are immunized with the appropriate toxin. Passively acquired immunity usually lasts no more than a month, but it manifests itself immediately after the administration of the therapeutic serum. A timely administered therapeutic serum containing ready-made antibodies often provides a successful fight against a severe infection (for example, diphtheria), which develops so quickly that the body does not have time to produce a sufficient amount of antibodies and the patient may die.

Immunity through phagocytosis and the production of antibodies protects the body from infectious diseases, frees it from dead, degenerated and foreign cells, and causes rejection of transplanted foreign organs and tissues.

After some infectious diseases, immunity is not developed, for example, against a sore throat, which you can get sick with many times.

The third physiological compound of hemoglobin is carbohemoglobin - a compound of hemoglobin with carbon dioxide. Thus, hemoglobin is involved in the transfer of carbon dioxide from tissues to the lungs. Carbohemoglobin is found in venous blood.

When hemoglobin is exposed to strong oxidizing agents (berthollet salt, potassium permanganate, nitrobenzene, aniline, phenacetin, etc.), iron is oxidized and becomes trivalent. In this case, hemoglobin is converted into methemoglobin and acquires a brown color. Being a product of true oxidation of hemoglobin, the latter firmly retains oxygen and therefore cannot serve as its carrier. The formation of a significant amount of methemoglobin sharply worsens the respiratory functions of the blood. This can happen after the introduction of drugs with oxidizing properties into the body. Methemoglobin is a pathological compound of hemoglobin.

Hemoglobin very easily combines with carbon monoxide to form carboxyhemoglobin (HbCO). The chemical affinity of carbon monoxide for hemoglobin is approximately 200 times greater than that of oxygen. Therefore, it is enough to add a small amount of CO to the air to form a significant number of molecules of this compound. It is very strong, and hemoglobin, blocked by CO, cannot be an oxygen carrier. Therefore, carbon monoxide is very poisonous. When inhaling air containing 0.1% CO, severe consequences of oxygen starvation (vomiting, loss of consciousness) develop after 30-60 minutes. When the air contains 1% CO, death occurs within a few minutes. Affected people and animals must be taken out into clean air or allowed to breathe oxygen. Under the influence of high oxygen pressure, carboxyhemoglobin is slowly broken down.

When hydrochloric acid acts on hemoglobin, hemin is formed. In this compound, iron is in the oxidized trivalent form. To obtain it, a drop of dried blood is heated on a glass slide with crystals of table salt and 1-2 drops of glacial acetic acid. Brown orthorhombic crystals of hemin are examined under a microscope. Hemin crystals of different animal species differ in their shape. This is due to species differences in the structure of globin. This reaction, called the hemin test, can be used to detect traces of blood.

When viewing a diluted solution of oxyhemoglobin through a spectroscope, two characteristic dark absorption bands are visible in the yellow-green part of the spectrum, between the Fraunhofer lines D and E. Reduced hemoglobin is characterized by one wide absorption band in the yellow-green part of the spectrum. The spectrum of carboxyhemoglobin is very similar to that of oxyhemoglobin. They can be distinguished by the addition of a reducing agent. Carboxyhemoglobin and after that has two absorption bands. Methemoglobin has a characteristic spectrum: one narrow absorption band is on the left, on the border of the red and yellow parts of the spectrum, another narrow band on the border of the yellow and green zones, and a wide dark band in the green part.

The amount of hemoglobin is determined by the colorimetric method and expressed as a gram percent (g%), and then using the International System of Units (SI) conversion factor, which is equal to 10, the amount of hemoglobin is found in grams per liter (g/l). It depends on the type of animal. The content of red blood cells and hemoglobin is affected by age, gender, breed, altitude, work, feeding. Thus, newborn animals have a higher content of red blood cells and hemoglobin than adults; In males, the number of red blood cells is 5-10% higher than in females.

The number of erythrocytes in racehorses is greater than in draft horses, and reaches 10-10.5 million/µl of blood, or according to the SI system 10-10.5.1012 l, and in draft horses it is 7.4-7.6 million/µl

The decrease in oxygen pressure at high altitudes stimulates the formation of red blood cells. Therefore, in sheep and cows on mountain pastures the number of red blood cells and hemoglobin is increased. Intense physical activity produces the same effect. The amount of hemoglobin in the blood of trotters, equal to an average of 12.6 g% (126 g/l) before running, increases to 16-18 g% (160-180 g/l) after running. Deterioration of feeding leads to a decrease in the content of red blood cells and hemoglobin. The lack of microelements and vitamins (cyanocobalamin, folic acid, etc.) has a particularly large impact.

To determine the saturation of each red blood cell with hemoglobin, a color indicator or index I is used

Normally, the color index is 1. If it is less than 1, the hemoglobin content in red blood cells is reduced (hypochromia), if more than 1, it is increased (hyperchromia).

Myoglobin. Skeletal and cardiac muscles contain muscle hemoglobin (myoglobin). It has similarities and differences with blood hemoglobin. The similarity of these two substances is expressed by the presence of the same prosthetic group, the same amount of iron, and the ability to form reversible compounds with O and CO. However, the mass of myoglobin is much smaller, and it has a much greater affinity for oxygen than blood hemoglobin, and is therefore adapted to the function of storing (binding) oxygen, which is of great importance for supplying oxygen to contracting muscles. When muscles contract, their blood supply is temporarily reduced due to constriction of the capillaries. And at this moment, myoglobin serves as an important source of oxygen. It “stores” oxygen during relaxation and releases it during contraction. Myoglobin content increases under the influence of muscle loads.

Erythrocyte sedimentation rate (ESR). To determine ESR, blood is mixed with a solution of sodium citrate, and a test tube with millimeter graduations is collected in a glass tube. After some time, the height of the upper transparent layer is counted. ESR varies among animals of different species. Horse erythrocytes settle very quickly, and ruminants settle very slowly. The value of ESR is influenced by the physiological state of the body. Strenuous training slows down this reaction. In sports horses selected for Olympic competition, with an average load, the ESR in the first 15 minutes was 9.6 mm. After 2 months of intense training, in the same first 15 minutes it was 2.6 mm.

ESR increases greatly during pregnancy, as well as during chronic inflammatory processes, infectious diseases, and malignant tumors. This is associated with an increase in the amount of large molecular proteins in the plasma - globulins and especially fibrinogen. It is likely that large molecular proteins reduce the electrical charge and electrical repulsion of erythrocytes, which contributes to a greater rate of sedimentation.

Lifespan of red blood cells. It is different for different animals. Erythrocytes in a horse remain in the vascular bed for an average of 100 days, in cattle - 120-16, in a sheep - 130, in a reindeer - in a rabbit - 45-60 days.

In 1951, A.L. Chizhevsky, as a result of experimental studies and mathematical calculations, came to the conclusion that in the arterial vessels of healthy people and animals, red blood cells move in a system consisting of coin columns.

Moreover, coin columns of large diameter erythrocytes are adjacent to the slow parietal layer of blood, and coin columns of small diameter erythrocytes are carried in the fast axial blood flow. In addition to translational movement, red blood cells also perform rotational movements around their own axis. In diseases, the spatial arrangement of red blood cells in the vessels is disrupted.

Leukocytes. White blood cells have a cytoplasm and a nucleus. They are divided into two large groups: granular (granulocytes) and non-granular (agranulocytes). The cytoplasm of granular leukocytes contains grains (granules), while the cytoplasm of non-granular leukocytes contains no granules.

Granular leukocytes, depending on the color of the granules, are distinguished as eosinophilic (granules are painted pink with acidic dyes, such as eosin), basophilic (blue with basic dyes) and neutrophilic with both pink-violet dyes). In young granulocytes, the nucleus is round, in young it is in the form of a horseshoe or stick (rod); As it develops, the core is laced and divided into several segments. Segmented neutrophils make up the bulk of granulocytes.

In birds, instead of segmented neutrophils, there are pseudoeosinophils, the cytoplasm of which contains rod-shaped and spindle-shaped granules.

Non-granular leukocytes are divided into lymphocytes and monocytes. Lymphocytes have a large nucleus surrounded by a narrow belt of cytoplasm. Depending on the size, large, medium and small lymphocytes are distinguished. Lymphocytes make up the majority of white blood cells: in cattle

50-60% of all leukocytes, In pigs - 45-60, in sheep - 55-65, in goats - 40-50, in rabbits - 50-65, in chickens - 45-65%. These types of animals are characterized by the so-called lymphocytic blood profile. In horses and carnivores, segmented neutrophils predominate - the neutrophil profile of the blood. However, even in these animals the number of lymphocytes is significant - 20-40% of all leukocytes. Monocytes are the largest blood cells, mostly round in shape, with a well-defined cytoplasm.

In addition, the blood of birds contains Turkic cells - large, with an eccentrically located nucleus and a significant amount of cytoplasm.

The total number of leukocytes in the blood is significantly less than that of red blood cells. In mammals it is about 0.1--0.2% of the number of red blood cells, in birds it is slightly more (about 0.5--1%).

An increase in the number of leukocytes is called leukocytosis, and a decrease is called leukopenia.

There are two types of leukocytosis: physiological and reactive. Physiological, in turn, is divided into:

digestive (a significant increase in the number of leukocytes occurs after eating food; especially pronounced in horses, pigs, dogs and rabbits);

myogenic (develops after heavy muscular work);

emotional;

with painful effects;

during pregnancy.

Physiological leukocytoses are redistributive in nature, that is, leukocytes in these cases leave the depot (spleen, bone marrow, lymph nodes). They are characterized by rapid development, short duration, and absence of changes in the leukocyte formula.

Reactive, or true, leukocytosis occurs in inflammatory processes and infectious diseases. At the same time, the formation of white blood cells in the hematopoietic organs sharply increases and the number of leukocytes in the blood increases more significantly than with redistributive leukocytosis. But the main difference is that with reactive leukocytosis, the leukocyte formula changes: in the blood the number of young forms of neutrophils - myelocytes, young, and stab - increases. The severity of the disease and the reactivity of the body are assessed by the nuclear shift to the left.

Recently, leukopenias are more common than before. This is due to an increase in background radioactivity and other reasons related to technological progress. Particularly severe leukopenia caused by bone marrow damage is observed with radiation sickness. Leukopenia is also detected in some infectious diseases (calf paratyphoid fever, swine fever).

Functions of leukocytes. Leukocytes play an important role in the protective and regenerative processes of the body. Monocytes and neutrophils are capable of amoeboid movement. The speed of movement of the latter can reach up to 40 μm/m, which is equal to a distance 3-4 times greater than the diameter of these cells. These types of leukocytes pass through the endothelium of the capillaries and move in the tissues to the place of accumulation of microbes, foreign particles or decaying cells of the body itself. One neutrophil can capture up to 20-30 bacteria, and a monocyte phagocytoses up to 100 microbes. In addition to proteolytic enzymes, these forms of leukocytes secrete, also adsorb on their surface and transport substances that neutralize microbes and foreign proteins - antibodies.

Basophils have a weak ability for phagocytosis or do not show it at all. Like mast cells of connective tissue, they synthesize heparin, a substance that prevents blood clotting. In addition, basophils are capable of producing histamine. Heparin prevents blood clotting, and histamine expands the capillaries at the site of inflammation, which accelerates the process of resorption and healing.

Lymphocytes take part in the production of antibodies, therefore they are of great importance in creating immunity to infectious diseases (infectious immunity), and are also responsible for reactions to the introduction of foreign proteins and rejection of foreign tissue during organ transplantation (transplantation immunity).

The leading role in immunity, especially transplantation, is played by the so-called T-lymphocytes. They are formed from precursor cells in the bone marrow, undergo differentiation in the thymus (thymus gland), and then move to the lymph nodes, spleen or circulating blood, where they account for 40-70% of all lymphocytes. T lymphocytes are heterogeneous. Among them there are several groups:

1) helpers (assistants) interact with B lymphocytes and transform them into plasma cells that synthesize antibodies;

2) suppressors - suppress excessive reactions of B-lymphocytes and maintain a constant ratio of different forms of lymphocytes;

H) killers (killers) - interact with foreign cells and destroy them;

4) amplifiers - activate killers;

5) immune memory cells

B lymphocytes are formed in the bone marrow, differentiated in mammals in the lymphoid tissue of the intestine, appendix, pharyngeal and palatine tonsils. In birds, differentiation takes place in the bursa of Fabricius. The Latin word for bursa is bursa, hence B lymphocytes. They account for 20-30% of circulating lymphocytes. The main function of B lymphocytes is to produce antibodies and create humoral immunity. After meeting the antigen, B lymphocytes move to the bone marrow, spleen, and lymph nodes, where they multiply and turn into plasma cells that form antibodies and immune globulins. B lymphocytes are specific: each group of them reacts with only one antigen and is responsible for the production of antibodies only against it.

There are also so-called zero lymphocytes, which do not undergo differentiation in the organs of the immune system, but, if necessary, can turn into T and B lymphocytes. They make up 10-20% of lymphocytes.

Lifespan of leukocytes. Most of them live relatively short lives. Using the technique of labeled atoms, it was established that granulocytes live a maximum of 8-10 days, often much less - hours and even minutes. The average lifespan of neutrophils in a calf is 5 hours. Among lymphocytes, short-lived and long-lived forms are distinguished. The first (B-lymphocytes) live from several hours to a week, the second (T-lymphocytes) can live for months and even years.

Blood platelets (platelets). In mammals, these blood cells do not have nuclei; in birds and all lower vertebrates there are nuclei. Blood plates have the amazing property of changing shape and size depending on location. Thus, in the blood stream they have the shape of a ball with a diameter of half a micron (at the resolution limit of an optical microscope). But once on the wall of a blood vessel or on a glass slide, they spread out, from round to star-shaped, increasing their area by 5-10 times, their diameter becomes from 2 to 5 microns. The number of blood platelets depends on the type of animal. It increases with heavy muscular work, digestion, and during pregnancy. Daily fluctuations were also noted: there are more of them during the day than at night. The number of blood platelets decreases in acute infectious diseases and anaphylactic shock.

In 1882, the Russian scientist V.P. Obraztsov first proved that platelets are independent elements of the blood, originating from red bone marrow cells - megakaryocytes (diameter up to 140 microns). Megakaryocyte- a cell with a huge nucleus. For a long time, the “explosion theory” was accepted, according to which a “mature” megakaryocyte seems to explode, disintegrating into small particles - platelets. Moreover, the megakaryocyte nucleus also disintegrates, transferring a certain supply of the substance of heredity - DNA - to platelets. However, careful studies under an electron microscope did not confirm this hypothesis. It turned out that in the cytoplasm of a megakaryocyte, under the control of its giant nucleus, the conception and development of 3-4 thousand platelets occurs. The megakaryocyte then releases its cytoplasmic processes through the walls of the blood vessels. The processes contain mature blood platelets, they tear off, enter the bloodstream and begin to perform their functions. But the megakaryocyte does not cease to exist. Its nucleus grows new cytoplasm, in which a new cycle of birth, maturation and “birth” of plates takes place. Thus, the “explosion theory” was replaced by the “birth theory”. Each megakaryocyte produces 8-10 generations of platelets during its existence in the bone marrow. The plates are released into the blood from the bone marrow in a mature state with a full set of organelles, but without a nucleus and nuclear hereditary material (DNA). They exist, but do not develop, spend themselves, but do not recover. In the absence of a nucleus in the blood stream, only synthesis is possible due to the reserves of substances and energy received from the megakaryocyte. That is why each platelet does not live long in the bloodstream (3-5 days).

In a light microscope, the plates look like pieces of cytoplasm with a small number of grains inside. Using an electron microscope, it was shown that behind the apparent simplicity there is hidden a unique and complex organization. The chemical composition of blood platelets also turned out to be very complex. They contain the enzymes adrenaline, norepinephrine, lysozyme, ATP, serotonin granules and a number of other substances.

Functions of platelets. Platelets perform various functions. First of all, they are involved in the process of blood clotting.

Having a very sticky surface, they are able to quickly stick to the surface of a foreign object. When they come into contact with foreign bodies or a rough surface, platelets stick together, and then break up into small fragments, and at the same time substances lying in the mitochondria are released - the so-called lamellar, or platelet factors, which are usually denoted by Arabic numerals. They take part in all phases of blood coagulation.

Platelets serve as building materials for the primary thrombus. When blood clots, the blood platelets release tiny processes - star-shaped tendrils, then interlock with them, forming a frame on which a blood clot is formed - a thrombus.

Platelets also secrete substances necessary for the compaction of a blood clot - retractozymes. The most important of them is thrombostenin, which in its properties resembles skeletal muscle actomyosin.

Platelet-derived growth factor (TGF) is released from blood platelets into wounded tissue, which stimulates cell division, so the wound heals quickly.

Platelets strengthen the walls of blood vessels. The inner wall of the vessel is formed by epithelial cells, but its strength is determined by the adhesion of parietal platelets. And they are always located along the walls of blood vessels, serving as a kind of barrier. When the strength of the vessel wall is increased, the vast majority of wall platelets have a dendritic, most “tenacious” form, and many of them are at different stages of penetration into epithelial cells. Without interaction with platelets, the vascular endothelium begins to allow red blood cells to pass through.

Platelets transport various substances. For example, serotonin, which is adsorbed by platelets from the blood. This substance constricts blood vessels and reduces bleeding. Platelets also carry the so-called creative substances necessary to preserve the structure of the vascular wall. About 15% of platelets circulating in the blood are used for these purposes.

Platelets have the ability to phagocytose. They absorb and digest foreign particles, including viruses.

BLOOD CLOTTING

When a blood vessel is injured, the blood clots and a blood clot forms, which clogs the defect and prevents further bleeding. Blood clotting, or hemocoagulation, protects the body from blood loss and is the body’s most important protective reaction. With reduced blood clotting, even a minor injury can lead to death.

The rate of blood clotting varies among animals of different species. Blood clotting can occur inside blood vessels when their inner lining (intima) is damaged or due to increased blood clotting. In these cases, vascular blood clots form inside, which pose a danger to the body.

Blood coagulation is caused by a change in the physicochemical state of the plasma protein fibrinogen, which at the same time changes from a soluble to an insoluble form, turning into fibrin. Thin and long fibrin filaments form a network, in the loops of which there are formed elements. If you continuously stir the blood released from the vessel with a whisk, fibrin fibers will settle on it. Blood from which fibrin has been removed is called defibrinated. It consists of formed elements and serum. Blood serum- this is plasma in which there is no fibrinogen and some other substances involved in coagulation.

Not only whole blood, but also plasma can clot.

Modern theory of blood coagulation. It is based on the enzymatic theory of A. Schmidt (1872). According to the latest data, blood coagulation occurs in three phases: 1 - formation of prothrombinase, 2 - formation of thrombin, 3 - formation of fibrin.

In addition, the prephase and postphase of blood coagulation are distinguished. In the prephase, the so-called vascular-platelet, or microcirculatory, hemostasis is carried out. The post-phase includes two parallel processes: retraction (compaction) And fibrinolysis (dissolution) blood clot.

Hemostasis is a set of physiological processes that culminate in stopping bleeding when blood vessels are damaged. Vascular-platelet, or microcirculatory, hemostasis - stopping bleeding from small vessels with low blood pressure. It consists of two sequential processes: vasospasm and the formation of a platelet plug.

In case of injury, a reflex decrease in the lumen (spasm) of small blood vessels occurs. The reflex spasm is short-term. Longer vascular spasm is maintained by vasoconstrictor substances (serotonin, norepinephrine, adrenaline), which are secreted by platelets and damaged tissue cells. Vasospasm leads only to a temporary stop of bleeding.

The formation of a platelet plug is of primary importance for stopping bleeding in small vessels. A platelet plug is formed due to the ability of platelets to stick to a foreign surface (platelet adhesion) and stick together (platelet aggregation). The resulting platelet clot is then compacted as a result of the contraction of a special protein, thrombostenin, contained in platelets.

Stopping bleeding when small vessels are injured occurs in animals within 4 minutes. This hemostasis in vessels with low pressure is called primary. It is caused by prolonged spasm of blood vessels and mechanical blockage of platelet aggregates.

Secondary hemostasis ensures tight closure of damaged vessels by a thrombus. It protects against resumption of bleeding from small vessels and serves as the main mechanism of protection against bleeding when muscle-type vessels are damaged. In this case, irreversible platelet aggregation and clot formation occur.

In large vessels, hemostasis also begins with the formation of a platelet plug, but it cannot withstand high pressure and is washed out. In these vessels, coagulation (enzymatic) hemostasis takes place, carried out in three phases.

First phase. The formation of prothrombinase is the most complex and lengthy. There are tissue and blood and tissue prothrombinases.

The formation of tissue prothrombinase occurs in 5-10 s, and blood prothrombinase in 5-10 minutes.

The process of formation of tissue prothrombinase begins with damage to the walls of blood vessels and surrounding tissues and the release of tissue thrombin, which is fragments of cell membranes (phospholipids), into the blood. Substances contained in plasma, the so-called plasma factors, also take part in this process: VII - convertin, V - globulin - accelerator, X - thrombotropin and IV - calcium cations. The formation of tissue prothrombinase serves as a trigger for subsequent reactions.

The process of formation of blood prothrombinase begins with the activation of a special plasma substance - factor XII, or Hageman factor. In the circulating blood it is in an inactive state, which is due to the presence of an antifactor in the plasma that prevents its activation. Upon contact with a rough surface, the antifactor is destroyed, and then the Hageman factor is activated. The rough surface is the collagen fibers exposed when a blood vessel is damaged. With the activation of the Hageman factor, a chain reaction begins. Factor XII activates factor XI, a precursor of plasma thromboplastin, and forms a complex with it called contact factor. Under the influence of the contact factor, factor IX - antihemophilic globulin B is activated, which reacts with factor VIII antihemophilic globulin A - and calcium ions, forming a calcium complex.

The latter has a strong effect on blood platelets. They stick together, swell and secrete granules containing platelet factor Z. Contact factor, calcium complex and platelet factor form an intermediate product that activates factor X. The latter factor forms a complex on fragments of cell membranes, platelets and erythrocytes (blood thromboplastin) by combining with the factor V and calcium ions. This completes the formation of blood prothrombinase. The main link here is the active factor X.

Blood consists of formed elements (42-46%) erythrocytes (red blood cells), leukocytes (white blood cells) and platelets (blood platelets) and a liquid part plasma (54-58%). Blood plasma devoid of fibrinogen is called serum. In an adult, the total amount of blood is 5-8% of body weight, which corresponds to 5-6 liters. Blood volume is usually denoted in relation to body weight (ml? kg-1). On average, it is 65 ml * kg1 for men, 60 ml * kg-1 for women, and about 70 ml * kg-1 for children.

The number of red blood cells in the blood is about a thousand times higher than leukocytes, and tens of times higher than platelets. The latter are several times smaller in size than red blood cells. Therefore, red blood cells make up more than 90% of the total volume of blood cells. The ratio of the volume of formed elements to the total volume of blood, expressed as a percentage, is called hematocrit. In men, the hematocrit averages 46%, in women 42%. This means that in men, formed elements occupy 46%, and plasma 54% of the blood volume, and in women 42 and 58%, respectively. This difference is due to the fact that men have more red blood cells in their blood than women. Children have a higher hematocrit than adults; During aging, hematocrit decreases. An increase in hematocrit is accompanied by an increase in blood viscosity (its internal friction), which in a healthy adult is 4-5 units. Since peripheral resistance to blood flow is directly proportional to viscosity, any significant increase in hematocrit increases the load on the heart, as a result of which blood circulation in some organs may be impaired.

Blood performs a number of physiological functions in the body.

The transport function of blood is to transport all substances necessary for the functioning of the body (nutrients, gases, hormones, enzymes, metabolites).

The respiratory function consists of delivering oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs. Oxygen is transported predominantly by red blood cells in the form of a compound with hemoglobin oxyhemoglobin (HbO2), carbon dioxide by blood plasma in the form of bicarbonate ions (HCO3-). Under normal conditions, when breathing air, 1 g of hemoglobin adds 1.34 ml of oxygen, and since one liter of blood contains 140-160 g of hemoglobin, the amount of oxygen in it is about 200 ml; this value is usually called the oxygen capacity of the blood (sometimes this indicator is calculated per 100 ml of blood).

Thus, if we take into account that the total volume of blood in the human body is 5 liters, then the amount of oxygen associated with hemoglobin in it will be equal to about one liter.

The nutritional function of blood is due to the transfer of amino acids, glucose, fats, vitamins, enzymes and minerals from the digestive organs to tissues, systems and depots.

The thermoregulatory function is ensured by the participation of blood in the transfer of heat from the organs and tissues in which it is produced to the organs that give off heat, which maintains temperature homeostasis.

The excretory function is aimed at transferring metabolic products (urea, creatine, indican, uric acid, water, salts, etc.) from the places of their formation to the excretory organs (kidneys, lungs, sweat and salivary glands).

The protective function of blood, first of all, is the formation of immunity, which can be either innate or acquired. There are also tissue and cellular immunity. The first of them is caused by the production of antibodies in response to the entry of microbes, viruses, toxins, poisons, and foreign proteins into the body; the second is associated with phagocytosis, in which the leading role belongs to leukocytes, which actively destroy microbes and foreign bodies entering the body, as well as their own dying and mutagenic cells.

The regulatory function consists of both humoral (transfer of hormones, gases, minerals by blood) and reflex regulation associated with the influence of blood on vascular interoreceptors.

Formed elements of blood

The formation of blood cells is called hematopoiesis. It is carried out in various hematopoietic organs. The bone marrow produces red blood cells, neutrophils, eosinophils and basophils. Leukocytes are formed in the spleen and lymph nodes. Monocytes are formed in the bone marrow and in the reticular cells of the liver, spleen and lymph nodes. Platelets are produced in the red bone marrow and spleen.

Functions of red blood cells

The main physiological function of red blood cells is to bind and transport oxygen from the lungs to organs and tissues. This process is carried out due to the structural features of red blood cells and the chemical composition of hemoglobin.

Red blood cells are highly specialized anucleate blood cells with a diameter of 7-8 microns. Human blood contains 4.5-5-1012 * l-1 red blood cells. The shape of red blood cells in the form of a biconcave disk provides a large surface for the free diffusion of gases through its membrane. The total surface area of ​​all red blood cells in the circulating blood is about 3000 m2.

In the initial phases of their development, red blood cells have a nucleus and are called reticulocytes. Under normal conditions, reticulocytes make up about 1% of the total number of red blood cells circulating in the blood. An increase in the number of reticulocytes in peripheral blood may depend both on the activation of erythrocytosis and on the increased release of reticulocytes from the bone marrow into the bloodstream. The average lifespan of mature red blood cells is about 120 days, after which they are destroyed in the liver and spleen.

During the movement of blood, red blood cells do not settle, since they repel each other, since they have the same negative charges. When blood settles in a capillary, red blood cells settle to the bottom. The erythrocyte sedimentation rate (ESR) under normal conditions in men is 4-8 mm per 1 hour, in women 6-10 mm per 1 hour.

As red blood cells mature, their nucleus is replaced by the respiratory pigment hemoglobin (Hb), which makes up about 90% of the dry matter of red blood cells, and 10% is mineral salts, glucose, proteins and fats. Hemoglobin is a complex chemical compound whose molecule consists of the globin protein and the iron-containing part heme. Hemoglobin has the ability to easily combine with acid/fool and just as easily give it away. Combining with oxygen, it becomes oxyhemoglobin (HbO2, and by giving it away it turns into reduced (reduced) hemoglobin. Hemoglobin in human blood makes up 14-15% of its mass, i.e. about 700 g.

Skeletal and cardiac muscles contain a protein similar in structure to myoglobin (muscle hemoglobin). It combines with oxygen more actively than hemoglobin, providing it to working muscles. The total amount of myoglobin in humans is about 25% of blood hemoglobin. Myoglobin is found in greater concentrations in muscles that perform functional loads. Under the influence of physical activity, the amount of myoglobin in the muscles increases.

Functions of leukocytes

According to functional and morphological characteristics, leukocytes are ordinary cells containing a nucleus and protoplasm. The number of leukocytes in the blood of a healthy person is 4 6 * 109 * l-1. Leukocytes are heterogeneous in their structure: in some of them the protoplasm has a granular structure (granulocytes), and in others there is no granularity (agranulocytes). Granulocytes make up 65-70% of all leukocytes and are divided depending on the ability to stain with neutral, acidic or basic dyes into neutrophils, eosinophils and basophils.

Agranulocytes make up 30-35% of all white blood cells and include lymphocytes and monocytes. The functions of different leukocytes are varied.

The percentage of different forms of leukocytes in the blood is called the leukocyte formula. The total number of leukocytes and the leukocyte formula are not constant. An increase in the number of leukocytes in peripheral blood is called leukocytosis, and a decrease is called leukopenia. The lifespan of leukocytes is 7-10 days.

Neutrophils make up 60-70% of all white blood cells and are the most important cells in the body's defense against bacteria and their toxins. Penetrating through the walls of capillaries, neutrophils enter the interstitial spaces, where phagocytosis occurs - the absorption and digestion of bacteria and other foreign protein bodies.

Eosinophils (1-4% of the total number of leukocytes) adsorb antigens (foreign proteins), many tissue substances and protein toxins onto their surface, destroying and neutralizing them. In addition to the detoxification function, eosinophils take part in preventing the development of allergic reactions.

Basophils make up no more than 0.5% of all leukocytes and carry out the synthesis of heparin, which is part of the anticoagulation system of the blood. Basophils are also involved in the synthesis of a number of biologically active substances and enzymes (histamine, serotonin, RNA, phosphatase, lipase, peroxidase).

Lymphocytes (25-30% of all leukocytes) play a vital role in the formation of the body's immunity, and are also actively involved in neutralizing various toxic substances.

The main factors of the immunological system of the blood are T- and B-lymphocytes. T lymphocytes primarily play the role of a strict immune controller. Having come into contact with any antigen, they remember its genetic structure for a long time and determine the program for the biosynthesis of antibodies (immunoglobulins), which is carried out by B lymphocytes. B-lymphocytes, having received a program for the biosynthesis of immunoglobulins, turn into plasma cells, which are an antibody factory.

T-lymphocytes synthesize substances that activate phagocytosis and protective inflammatory reactions. They monitor the genetic purity of the body, preventing the engraftment of foreign tissues, activating regeneration and destroying dead or mutant (including tumor) cells of their own body. T-lymphocytes also play an important role as regulators of hematopoietic function, which consists in the destruction of foreign stem cells in the south of the brain. L lymphocytes are capable of synthesizing beta and gamma globulins, which are part of antibodies.

Unfortunately, lymphocytes cannot always fulfill their role in the formation of an effective immune system. In particular, the human immunodeficiency virus (HIV), which causes the terrible disease AIDS (acquired immunodeficiency syndrome), can sharply reduce the body's immunological defense. The main trigger for AIDS is the penetration of HIV from the blood into T-lymphocytes. There, the virus can remain in an inactive, latent state for several years, until immunological stimulation of T-lymphonitis begins in connection with a secondary infection. Then the virus is activated and multiplies so rapidly that the viral cells, leaving the affected lymphocytes, completely damage the membrane and destroy them. The progressive death of lymphocytes reduces the body's resistance to various intoxications, including microbes that are harmless to a person with normal immunity. In addition, the destruction of mutant (cancer) cells by T lymphocytes is sharply weakened, and therefore the likelihood of malignant tumors significantly increases. The most common manifestations of AIDS are. pneumonia, tumors, central nervous system lesions and pustular diseases of the skin and mucous membranes.

Primary and secondary disorders in AIDS cause a variegated picture of changes in peripheral blood. Along with a significant decrease in the number of lymphocytes, neutrophilic leukocytosis may occur in response to inflammation or pustular lesions of the skin (mucous membranes). When the blood system is damaged, foci of pathological hematopoiesis appear and immature forms of leukocytes will enter the blood in large quantities. With internal bleeding and exhaustion of the patient, progressive anemia begins to develop with a decrease in the number of red blood cells and hemoglobin in the blood.

Monocytes (4-8%) are the largest white blood cells, called macrophages. They have the highest phagocytic activity in relation to the breakdown products of cells and tissues, and also neutralize toxins formed in areas of inflammation. It is also believed that monocytes take part in the production of antibodies. Macrophages, along with monocytes, include reticular and endothelial cells of the liver, spleen, bone marrow and lymph nodes.

Platelet functions

Platelets are small, anucleate blood platelets (Bizzoceri plaques) of irregular shape, 2-5 microns in diameter. Despite the absence of a nucleus, platelets have an active metabolism and are the third independent living blood cell. Their number in peripheral blood ranges from 250 to 400 * 10 9 * l -1; The lifespan of platelets is 8-12 days.

Platelets play a leading role in blood clotting. Lack of platelets in the blood thrombopenia is observed in some diseases and is expressed in increased bleeding.

Physicochemical properties of blood plasma

Blood and human plasma is a colorless liquid containing 90-92% water and 8-10% solids, which include glucose, proteins, fats, various salts, hormones, vitamins, metabolic products, etc. Physicochemical properties of plasma determined by the presence of organic and mineral substances in it, they are relatively constant and are characterized by a number of stable constants.

The specific gravity of plasma is 1.02-1.03, and the specific gravity of blood is 1.05-1.06; in men it is slightly higher (more red blood cells) than in women.

Osmotic pressure is the most important property of plasma. It is inherent in solutions separated from each other by semi-permeable membranes, and is created by the movement of solvent (water) molecules through the membrane towards a higher concentration of soluble substances. The force that drives and moves the solvent, ensuring its penetration through a semipermeable membrane, is called osmotic pressure. Mineral salts play the main role in the osmotic pressure. In humans, the osmotic pressure of the blood is about 770 kPa (7.5-8 atm). That part of the osmotic pressure that is due to plasma proteins is called oncotic. Of the total osmotic pressure, proteins account for approximately 1/200, which is approximately 3.8 kPa.

Blood cells have the same osmotic pressure as plasma. A solution having an osmotic pressure equal to blood pressure is optimal for formed elements and is called isotonic. Solutions of lower concentration are called hypotonic; water from these solutions enters the red blood cells, which swell and can rupture; they undergo hemolysis. If a lot of water is lost from the blood plasma and the concentration of salts in it increases, then, due to the laws of osmosis, water from the red blood cells begins to enter the plasma through their semi-permeable membrane, which causes wrinkling of the red blood cells; Such solutions are called hypertonic. The relative constancy of osmotic pressure is ensured by osmoreceptors and is realized mainly through the excretory organs.

The acid-silk state is one of the important constants of the liquid internal environment of the body and is an active reaction determined by the quantitative ratio of H+ and OH- ions. Pure water contains equal amounts of H+ and OH- ions, so it is neutral. If the number of H+ ions per unit volume of solution exceeds the number of OH- ions, the solution has an acidic reaction; if the ratio of these ions is the opposite, the solution is alkaline. To characterize the active reaction of the blood, the hydrogen index, or pH, is used, which is the negative decimal logarithm of the concentration of hydrogen ions. In chemically pure water at a temperature of 25°C, the pH is 7 (neutral reaction). An acidic environment (acidosis) has a pH below 7, an alkaline environment (alkalosis) has a pH above 7. The blood has a slightly alkaline reaction: the pH of arterial blood is 7.4; The pH of venous blood is 7.35, which is due to the high content of carbon dioxide in it.

Blood buffer systems ensure the maintenance of relative constancy of the active blood reaction, i.e., they regulate the acid-base state. This ability of the blood is due to the special physicochemical composition of buffer systems that neutralize acidic and alkaline products that accumulate in the body. Buffer systems consist of a mixture of weak acids with their salts formed by strong bases. There are 4 buffer systems in the blood: 1) bicarbonate buffer system carbonic acid-sodium bicarbonate (H2CO3 NaHCO3), 2) phosphate buffer system monobasic-dibasic sodium phosphate (NaH2PO4-Na2HPO4); 3) hemoglobin buffer system reduced hemoglobin-potassium salt of hemoglobin (HHv-KHvO2); 4) plasma protein buffer system. In maintaining the buffering properties of blood, the leading role belongs to hemoglobin and its salts (about 75%), to a lesser extent to bicarbonate, phosphate buffers and plasma proteins. Plasma proteins play the role of a buffer system due to their amphoteric properties. In an acidic environment they behave like alkalis, binding acids. In an alkaline environment, proteins react as acids that bind alkalis.

All buffer systems create an alkaline reserve in the blood, which is relatively constant in the body. Its value is measured by the number of milliliters of carbon dioxide that can be bound by 100 ml of blood at a CO2 tension in plasma equal to 40 mmHg. Art. Normally it is equal to 50-65 volume percent CO2. Reserve alkalinity of the blood acts primarily as a reserve of buffer systems against a shift in pH to the acidic side.

The colloidal properties of blood are provided mainly by proteins and, to a lesser extent, by carbohydrates and lipoids. The total amount of proteins in blood plasma is 7-8% of its volume. Plasma contains a number of proteins that differ in their properties and functional significance: albumins (about 4.5%), globulins (2-3%) and fibrinogen (0.2-0.4%).

Blood plasma proteins function as regulators of complete exchange between blood and tissues. The viscosity and buffering properties of blood depend on the amount of proteins; they play an important role in maintaining plasma oncotic pressure.

Blood clotting and transfusion

The liquid state of the blood and the closedness of the bloodstream are necessary conditions for the life of the body. These conditions are created by the blood coagulation system (hemocoagulation system), which keeps circulating blood in a liquid state and prevents its loss through damaged vessels through the formation of blood clots; stopping bleeding is called hemostasis.

At the same time, in case of large blood losses, some poisonings and diseases, there is a need for blood transfusion, which must be carried out with strict adherence to its compatibility.

Blood clotting

The founder of the modern enzymatic theory of blood coagulation is Professor of Dorpat (Tartu) University A. A. Schmidt (1872). Subsequently, this theory was significantly expanded and it is currently believed that blood coagulation goes through three phases: 1) the formation of prothrombinase, 2) the formation of thrombin, 3) the formation of fibrin.

The formation of prothrombinase is carried out under the influence of thromboplastin (thrombokinase), which is phospholipids of degrading platelets, tissue cells and blood vessels. Thromboplastin is formed with the participation of Ca2+ ions and some plasma coagulation factors.

The second phase of blood coagulation is characterized by the conversion of inactive prothrombin of blood platelets under the influence of prothrombinase into active thrombin. Prothrombin is a glucoprotein formed by liver cells with the participation of vitamin K.

In the third phase of coagulation, insoluble fibrin protein is formed from soluble blood fibrinogen, activated by thrombin, the threads of which form the basis of a blood clot (thrombus), stopping further bleeding. Fibrin also serves as a structural material in wound healing. Fibrinogen is the largest molecular protein in plasma and is produced in the liver.

Blood transfusion

The founders of the doctrine of blood groups and the possibility of transfusion from one person to another were K. Landsteiner (1901) and J. Jansky (1903). In our country, blood transfusion was first carried out by the professor of the Military Medical Academy V.N. Shamov in 1919, and in 1928 he was offered a transfusion of cadaveric blood, for which he was awarded the Lenin Prize.

Ya. Jansky identified four blood groups found in people. This classification has not lost its meaning to this day. It is based on a comparison of antigens found in red blood cells (agglutinogens) and antibodies found in plasma (agglutinins). The main agglutinogens A and B and the corresponding agglutinins alpha and beta were isolated. Agglutinogen A and agglutinin alpha, as well as B and beta, are called the same name. Human blood cannot contain substances of the same name. When they meet, an agglutination reaction occurs, i.e. adhesion of red blood cells, and subsequently destruction (hemolysis). In this case, they talk about blood incompatibility.

Red blood cells classified as group I (0) do not contain agglutinogens, while plasma contains alpha and beta agglutinins. Group II (A) erythrocytes contain agglutinogen A, and plasma contains agglutinin beta. Blood group III (B) is characterized by the presence of agglutinogen B in erythrocytes and agglutinin alpha in plasma. IV (AB) blood group is characterized by the content of agglutinogens A and B and the absence of agglutinins.

Transfusion of incompatible blood causes transfusion shock, a serious pathological condition that can result in the death of a person. Table 1 shows in which cases when blood is transfused from a donor (the person giving blood) to a recipient (the person receiving blood)! agglutination (indicated by a + sign).

Table 1.

People of the first (I) group can be transfused with blood only from this group, and this group can also be transfused into people of all other groups. Therefore, people with group I are called universal donors. People of group IV can be transfused with blood of the same name, as well as blood of all other groups, therefore these people are called universal recipients. The blood of people of groups II and III can be transfused to people with the same name, as well as with group IV. These patterns are reflected in Fig. 1.

Rh compatibility is important during blood transfusion. It was first discovered in the red blood cells of rhesus monkeys. Subsequently, it turned out that the Rh factor is contained in the red blood cells of 85% of people (Rh-positive blood) and is absent in only 15% of people (Rh-negative blood). When repeating blood transfusion to a recipient who is incompatible with the donor's Rh factor, complications arise due to agglutination of incompatible donor red blood cells. This is the result of the action of specific anti-Rhesus agglutinins produced by the reticuloendothelial system after the first transfusion.

When an Rh-positive man marries an Rh-negative woman (which often happens), the fetus often inherits the father's Rh factor. The fetal blood enters the mother's body, causing the formation of anti-Rhesus agglutinins, which lead to hemolysis of the red blood cells of the unborn child. However, for pronounced disorders in the first child, their concentration is insufficient and, as a rule, the fetus is born alive, but with hemolytic jaundice. With repeated pregnancy, the concentration of anti-Rhesus substances in the mother’s blood sharply increases, which is manifested not only by hemolysis of the fetus’s red blood cells, but also by intravascular coagulation, often leading to its death and miscarriage.

Rice. 1.

Regulation of the blood system

Regulation of the blood system includes maintaining a constant volume of circulating blood, its morphological composition and the physicochemical properties of plasma. There are two main mechanisms for regulating the blood system in the body: nervous and humoral.

The highest subcortical center that carries out nervous regulation of the blood system is the hypothalamus. The cerebral cortex also influences the blood system through the hypothalamus. The efferent influences of the hypothalamus include the mechanisms of hematopoiesis, blood circulation and blood redistribution, its deposition and destruction. Receptors in the bone marrow, liver, spleen, lymph nodes and blood vessels perceive the changes occurring here, and afferent impulses from these receptors serve as a signal for corresponding changes in the subcortical regulatory centers. The hypothalamus, through the sympathetic division of the autonomic nervous system, stimulates hematopoiesis, enhancing erythropoiesis. Parasympathetic nervous influences inhibit erythropoiesis and redistribute leukocytes: a decrease in their number in peripheral vessels and an increase in the vessels of internal organs. The hypothalamus also takes part in the regulation of osmotic pressure, maintaining the required level of blood sugar and other physicochemical constants of the blood plasma.

The nervous system has both direct and indirect regulatory effects on the blood system. The direct path of regulation lies in the bilateral connections of the nervous system with the organs of hematopoiesis, blood distribution and blood destruction. Afferent and efferent impulses go in both directions, regulating all processes of the blood system. The indirect connection between the nervous system and the blood system is carried out with the help of humoral intermediaries, which, influencing the receptors of the hematopoietic organs, stimulate or weaken hematopoiesis.

Among the mechanisms of humoral regulation of blood, a special role belongs to biologically active glycoproteins - hematopoietins, synthesized mainly in the kidneys, as well as in the liver and spleen. The production of red blood cells is regulated by erythropoietins, leukocytes by leukopoietins and platelets by thrombopoietins. These substances enhance hematopoiesis in the bone marrow, spleen, liver, and reticuloendothelial system. The concentration of hematopoietins increases with a decrease in the formed elements in the blood, but in small quantities they are constantly contained in the blood plasma of healthy people, being physiological stimulators of hematopoiesis.

Hormones of the pituitary gland (somatotropic and adrenocorticotropic hormones), the adrenal cortex (glucocorticoids), and male sex hormones (androgens) have a stimulating effect on hematopoiesis. Female sex hormones (estrogens) reduce hematopoiesis, so the content of red blood cells, hemoglobin and platelets in the blood of women is less than that of men. There are no differences in the blood picture between boys and girls (before puberty), and they are also absent among older people.