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Formed elements of blood. How does donation work?

Let us consider in more detail the composition of plasma and cellular elements of blood.

Plasma. After the separation of cellular elements suspended in the blood, what remains is water solution complex composition, called plasma. As a rule, plasma is a clear or slightly opalescent liquid, the yellowish color of which is determined by the presence of small amounts of bile pigment and other colored organic substances.

However, after consumption fatty foods Many fat droplets (chylomicrons) enter the blood, causing the plasma to become cloudy and oily.

Plasma is involved in many vital processes of the body. It transports blood cells nutrients and metabolic products and serves as a link between all extravascular (i.e. located outside the blood vessels) fluids; the latter include, in particular, the intercellular fluid, and through it communication with the cells and their contents occurs. Thus, the plasma comes into contact with the kidneys, liver and other organs and thereby maintains the constancy of the internal environment of the body, i.e. homeostasis.

The main components of plasma and their concentrations are given in table. 1. Among the substances dissolved in plasma are low molecular weight organic compounds (urea, uric acid, amino acids, etc.); large and very complex protein molecules; partially ionized inorganic salts. The most important cations (positively charged ions) include sodium (Na +), potassium (K +), calcium (Ca 2+) and magnesium (Mg 2+) cations; The most important anions (negatively charged ions) are chloride anions (Cl –), bicarbonate (HCO 3 –) and phosphate (HPO 4 2– or H 2 PO 4 –). The main protein components of plasma are albumin, globulins and fibrinogen.

Plasma proteins

Of all proteins, albumin, synthesized in the liver, is present in the highest concentration in plasma. It is necessary to maintain osmotic balance, which ensures normal distribution of fluid between blood vessels and the extravascular space. During fasting or insufficient protein intake from food, the albumin content in plasma decreases, which can lead to increased accumulation of water in tissues (edema). This condition, associated with protein deficiency, is called starvation edema.

Plasma contains globulins of several types, or classes, the most important of which are designated by the Greek letters a (alpha), b (beta) and g (gamma), and the corresponding proteins are a 1, a 2, b, g 1 and g 2. After separation of globulins (by electrophoresis), antibodies are detected only in fractions g 1, g 2 and b. Although antibodies are often called gamma globulins, the fact that some of them are also present in the b-fraction led to the introduction of the term “immunoglobulin”. The a- and b-fractions contain many different proteins that ensure the transport of iron, vitamin B12, steroids and other hormones in the blood. This same group of proteins also includes coagulation factors, which, along with fibrinogen, are involved in the process of blood clotting.

The main function of fibrinogen is to form blood clots (thrombi). During the process of blood clotting, whether in vivo (in a living body) or in vitro (outside the body), fibrinogen is converted into fibrin, which forms the basis of a blood clot; Plasma that does not contain fibrinogen, usually in the form of a clear, pale yellow liquid, is called blood serum.

Red blood cells.

Red blood cells, or erythrocytes, are round discs with a diameter of 7.2–7.9 µm and an average thickness of 2 µm (µm = micron = 1/10 6 m). 1 mm 3 of blood contains 5–6 million red blood cells. They make up 44–48% of the total blood volume.

Red blood cells have the shape of a biconcave disc, i.e. The flat sides of the disk are compressed, making it look like a donut without a hole. Mature red blood cells do not have nuclei. They contain mainly hemoglobin, the concentration of which in the intracellular aqueous medium is approx. 34%. [In terms of dry weight, the hemoglobin content in erythrocytes is 95%; per 100 ml of blood, the hemoglobin content is normally 12–16 g (12–16 g%), and in men it is slightly higher than in women.] In addition to hemoglobin, red blood cells contain dissolved inorganic ions (mainly K +) and various enzymes . The two concave sides provide the red blood cell with optimal surface area through which gases can be exchanged: carbon dioxide and oxygen. Thus, the shape of the cells largely determines the efficiency of the process. physiological processes. In humans, the area of surfaces through which gas exchange occurs averages 3820 m2, which is 2000 times the surface of the body.

In the fetus, primitive red blood cells are first formed in the liver, spleen and thymus. From the fifth month of intrauterine development, erythropoiesis gradually begins in the bone marrow - the formation of full-fledged red blood cells. In exceptional circumstances (for example, when replacing a normal bone marrow cancerous tissue), the adult body can switch back to producing red blood cells in the liver and spleen. However, in normal conditions erythropoiesis in an adult man is walking only in flat bones (ribs, sternum, pelvic bones, skull and spine).

Red blood cells develop from precursor cells, the source of which is the so-called. stem cells. In the early stages of red blood cell formation (in cells still in the bone marrow), the cell nucleus is clearly visible. As the cell matures, hemoglobin accumulates, formed during enzymatic reactions. Before entering the bloodstream, the cell loses its nucleus - due to extrusion (squeezing out) or destruction by cellular enzymes. With significant blood loss, red blood cells are formed faster than normal, and in this case, immature forms containing a nucleus may enter the bloodstream; This apparently occurs because the cells leave the bone marrow too quickly. The period of maturation of erythrocytes in the bone marrow - from the moment the youngest cell appears, recognizable as the precursor of an erythrocyte, until its full maturation - is 4-5 days. The lifespan of a mature erythrocyte in peripheral blood is on average 120 days. However, with certain abnormalities of these cells themselves, a number of diseases, or under the influence of certain medicines The lifespan of red blood cells may be shortened.

Most of the red blood cells are destroyed in the liver and spleen; in this case, hemoglobin is released and breaks down into its components heme and globin. The further fate of globin was not traced; As for heme, iron ions are released from it (and returned to the bone marrow). Losing iron, heme turns into bilirubin, a red-brown bile pigment. After minor modifications occurring in the liver, bilirubin in bile is excreted through gallbladder V digestive tract. Based on the content of the final product of its transformations in feces, the rate of destruction of red blood cells can be calculated. On average, in an adult body, 200 billion red blood cells are destroyed and re-formed every day, which is approximately 0.8% of their total number (25 trillion).

Hemoglobin.

The main function of the red blood cell is to transport oxygen from the lungs to the tissues of the body. A key role in this process is played by hemoglobin, an organic red pigment consisting of heme (a porphyrin compound with iron) and globin protein. Hemoglobin has a high affinity for oxygen, due to which the blood is able to carry much more oxygen than a regular aqueous solution.

The degree of binding of oxygen to hemoglobin depends primarily on the concentration of oxygen dissolved in the plasma. In the lungs, where there is a lot of oxygen, it diffuses from the pulmonary alveoli through the walls of blood vessels and the aqueous medium of the plasma and enters the red blood cells; There it binds to hemoglobin - oxyhemoglobin is formed. In tissues where the oxygen concentration is low, oxygen molecules are separated from hemoglobin and penetrate into the tissue due to diffusion. Insufficiency of red blood cells or hemoglobin leads to a decrease in oxygen transport and thereby to disruption of biological processes in tissues.

In humans, a distinction is made between fetal hemoglobin (type F, from fetus) and adult hemoglobin (type A, from adult). There are many known genetic variants of hemoglobin, the formation of which leads to abnormalities of red blood cells or their function. Among them, the most famous is hemoglobin S, which causes sickle cell anemia.

Leukocytes.

White peripheral blood cells, or leukocytes, are divided into two classes depending on the presence or absence of special granules in their cytoplasm. Cells that do not contain granules (agranulocytes) are lymphocytes and monocytes; their kernels have a predominantly regular round shape. Cells with specific granules (granulocytes) are usually characterized by the presence of irregularly shaped nuclei with many lobes and are therefore called polymorphonuclear leukocytes. They are divided into three types: neutrophils, basophils and eosinophils. They differ from each other in the pattern of granules stained with various dyes.

In a healthy person, 1 mm 3 of blood contains from 4,000 to 10,000 leukocytes (on average about 6,000), which is 0.5–1% of blood volume. Ratio individual species The number of cells in white blood cells can vary significantly from person to person and even from one person to another at different times. Typical values are given in table. 2.

Polymorphonuclear leukocytes (neutrophils, eosinophils and basophils) are formed in the bone marrow from progenitor cells, which give rise to stem cells, probably the same ones that give rise to red blood cell precursors. As the nucleus matures, the cells develop granules that are typical for each cell type. In the bloodstream, these cells move along the walls of the capillaries primarily due to amoeboid movements. Neutrophils are able to leave the internal space of the vessel and accumulate at the site of infection. The lifespan of granulocytes appears to be approx. 10 days, after which they are destroyed in the spleen.

The diameter of neutrophils is 12–14 µm. Most dyes color their core purple; the nucleus of peripheral blood neutrophils can have from one to five lobes. The cytoplasm is stained pinkish; under a microscope, many intense pink granules can be distinguished in it. In women, approximately 1% of neutrophils carry sex chromatin (formed by one of the two X chromosomes), a drumstick-shaped body attached to one of the nuclear lobes. These so-called Barr bodies allow sex to be determined by examining blood samples.

Eosinophils are similar in size to neutrophils. Their nucleus rarely has more than three lobes, and the cytoplasm contains many large granules, which clearly stain bright red with eosin dye.

Unlike eosinophils, basophils have cytoplasmic granules stained blue with basic dyes.

Monocytes. The diameter of these non-granular leukocytes is 15–20 µm. The nucleus is oval or bean-shaped, and only in a small part of the cells is it divided into large lobes that overlap each other. When stained, the cytoplasm is bluish-gray and contains a small number of inclusions that are stained blue-violet with azure dye. Monocytes are formed both in the bone marrow and in the spleen and lymph nodes. Their main function is phagocytosis.

Lymphocytes. These are small mononuclear cells. Most peripheral blood lymphocytes have a diameter of less than 10 µm, but lymphocytes with a larger diameter (16 µm) are sometimes found. The cell nuclei are dense and round, the cytoplasm is bluish in color, with very sparse granules.

Although lymphocytes appear morphologically uniform, they differ clearly in their functions and cell membrane properties. They are divided into three broad categories: B cells, T cells, and O cells (null cells, or neither B nor T).

B lymphocytes mature in the human bone marrow and then migrate to the lymphoid organs. They serve as precursors to cells that form antibodies, the so-called. plasmatic. In order for B cells to transform into plasma cells, the presence of T cells is necessary.

T cell maturation begins in the bone marrow, where prothymocytes are formed, which then migrate to the thymus gland, an organ located in the chest behind the breastbone. There they differentiate into T lymphocytes, a highly heterogeneous population of immune system cells that perform various functions. Thus, they synthesize macrophage activation factors, B-cell growth factors and interferons. Among T cells there are inducer (helper) cells that stimulate the formation of antibodies by B cells. There are also suppressor cells that suppress the functions of B cells and synthesize the growth factor of T cells - interleukin-2 (one of the lymphokines).

O cells differ from B and T cells in that they do not have surface antigens. Some of them serve as “natural killers”, i.e. kill cancer cells and cells infected with a virus. However, the overall role of O cells is unclear.

· blood is a liquid connective tissue of mesodermal origin. Together with tissue fluid and lymph, it forms the internal environment of the body. Blood performs a variety of functions. The most important of them: transport of nutrients to tissues (* trophic function), transport of metabolic products from tissues (excretory function ), transport of gases (oxygen and carbon dioxide) from the lungs to tissues and back (respiratory function), transport of hormones (humoral function), protection. function, blood coagulation, preventing blood loss, thermoregular function (regulation of heat transfer), gnomeostatic function_maintenance of constancy of internal. orgasmic environment!

· Blood composition - blood consists of a liquid part - plasma and cells suspended in it - shaped elements: erythrocytes (red blood cells), leukocytes (white blood cells) and platelets (blood platelets). Blood is the same tissue of the body as all the others, only it is liquid! Blood is in constant movement and performs a responsible function - it delivers oxygen and nutrients to the cells of the body. Thanks to hemoglobin contained in red blood cells, blood has a red color. Blood consists of 2 main components: plasma and substances suspended in it, which are called formed substances. The ratio of the amount of plasma (40-45%) and formed substances (55-60%) is called the hematocrit number (hematocrit).
In turn, blood plasma consists of 90% water and another 10% of it consists of dissolved fats, carbohydrates, salts, trace elements, hormones and other substances. The formed elements of blood are represented by erythrocytes, platelets and leukocytes. Blood is a rapidly renewing tissue.
Regeneration of blood cells is carried out due to the destruction of old cells and the formation of new ones by the hematopoietic organs, the main one of which is the bone marrow. The average amount of blood in the body of an adult is 6-8% of the total mass; in a child it is slightly higher: 8-9%. The average blood volume in an adult male is approximately 5-6 liters.
The total amount of blood may increase briefly after drinking large amounts of fluids and absorbing water from the intestines. However, excess water from the body in a healthy person is removed relatively quickly through the kidneys. A temporary decrease in the amount of blood is observed with blood loss. Rapid loss of a diseased amount of blood (up to 1/3 - 1/2 of the total volume) can cause death.

· 16. Morphophysiological features of the blood system in children and adolescents

· Blood volume. The absolute volume of blood increases with age: in newborns it is 0.5 l, in adults - 4-6 l. Relative to body weight, blood volume decreases with age: in newborns - 150 ml/kg body weight, at 1 year - 110, at 6 years, 12-16 years - 70 ml/kg body weight.

· Circulating blood volume (CBV). Unlike adults, children have almost all their blood circulating, i.e. BCC approaches blood volume. For example, BCC in 7-12 year old children is 70 ml/kg body weight.

· Hematocrit number. In newborns, the proportion of formed elements is 57% of the total blood volume, at 1 month - 45%, at 1-3 years - 35%, at 5 years - 37%, at 11 years - 39%, at 16 years - 42-47 %.

· Number of red blood cells in 1 liter. blood. In a newborn it is 5.8; at 1 month - 4.7; from 1 year to 15 years - 4.6, and at 16-18 years it reaches values typical for adults.

· Average erythrocyte diameter (µm). In newborns - 8.12; at 1 month - 7.83; at 1 year - 7.35; at 3 years - 7.30; at 5 years old - 7.30; at 10 years old - 7.36; at 14-17 years old - 7.50.

· Lifespan of a red blood cell. In newborns it is 12 days, on the 10th day of life - 36 days, and per year, as in adults - 120 days.

· Osmotic stability of red blood cells. In newborns, the minimum resistance of erythrocytes is lower than in adults (0.48-0.52% NaCI solution versus 0.44-0.48%); however, by 1 month it becomes the same as in adults.

· Hemoglobin. In newborns, its level is 215 g/l, at 1 month - 145, at 1 year - 116, at 3 years - 120, at 5 years - 127, at 7 years - 127, at 10 years - 130, at 14 - 17 years - 140-160 g/l. The replacement of fetal hemoglobin (HbF) with adult hemoglobin (HbA) occurs by 3 years.

· Color indicator. In a newborn it is 1.2; at 1 month - 0.85; at 1 year - 0.80; at 3 years - 0.85; at 5 years - 0.95; at 10 years old - 0.95; at 14-17 years old - 0.85-1.0.

· Erythrocyte sedimentation rate (ESR). In newborns it is 2.5 mm/hour, at 1 month - 5.0; at 1 year and older - 7.0-10 mm/hour.

· Leukocytes. In 1 liter of blood in a newborn - 30 x 109 leukocytes, in 1 month - 12.1 x 109, in 1 year - 10.5 x 109, in 3-10 years - 8-10 x 109, in 14-17 years - 5-8 x 109. Thus, there is a gradual decrease in red blood cells.

· Leukocyte formula. She has age characteristics associated with the content of neutrophils and lymphocytes. In newborns, as in adults, the share of neutrophils is 68%, and the share of lymphocytes is 25%; on the 5-6th day after birth, the so-called “first crossover” occurs - there are fewer neutrophils (up to 45%), and more lymphocytes (up to 40%). This ratio persists until approximately 5-6 years (“second cross”). For example, at 2-3 months the proportion of neutrophils is 25-27%, and the proportion of lymphocytes is 60-63%. This indicates a significant increase in the intensity of specific immunity in children of the first 5-6 years. After 5-6 years, gradually, by the age of 15, the ratio characteristic of adults is restored.

· T lymphocytes. In newborns, T-lymphocytes account for 33-56% of all forms of lymphocytes, and in adults - 60-70%. This situation occurs from the age of 2.

· Immunoglobulin production. Already in utero the fetus is able to synthesize

· Ig M (12 weeks), Ig G (20 weeks), Ig A (28 weeks). The fetus receives Ig G from the mother. In the first year of life, the child produces mainly Ig M and practically does not synthesize Ig G and Ig A. The lack of the ability to produce Ig A explains the high susceptibility of infants to intestinal flora. The level of the “adult” state is achieved for Ig M at 4-5 years, for Ig G at 5-6 years and for Ig A at 10-12 years. In general, the low content of immunoglobulins in the first year of life explains the high susceptibility of children to various diseases of the respiratory and digestive organs. The exception is the first three months of life - during this period there is almost complete immunity to infectious diseases, that is, a kind of unresponsiveness manifests itself.

· Indicators of nonspecific immunity. A newborn has phagocytosis, but it is “low-quality”, since it lacks the final stage. Phagocytosis reaches the level of the “adult” state after 5 years. A newborn already has lysozyme in saliva, tear fluid, blood, and leukocytes; and its level of activity is even higher than that of adults. The content of properdin (compliment activator) in a newborn is lower than in adults, but by 7 days of life it reaches these values. The content of interferons in the blood of newborns is as high as in adults, but in subsequent days it falls; lower content than in adults is observed from 1 year to 10-11 years; from 12-18 years old it reaches values characteristic of adults. The activity of the complement system in newborns is 50% of that of adults; by 1 month it becomes the same as in adults. Thus, in general, humoral nonspecific immunity in children is almost the same as in adults.

· Hemostasis system. The number of platelets in children of all ages, including newborns, is the same as in adults (200-400 x 109 per 1 l). Despite certain differences in the content of blood coagulation factors and anticoagulants, on average the coagulation rate in children, including newborns, is the same as in adults (for example, according to Bürker - 5-5.5 min); similarly - duration of bleeding (2-4 minutes according to Duke), plasma recalcification time, plasma tolerance to heparin. The exception is the prothrombin index and prothrombin time - in newborns they are lower than in adults; the ability of platelets to aggregate in newborns is also less pronounced than in adults. After a year, the content of coagulation factors and anticoagulants in the blood is the same as in adults.

· Physicochemical properties of blood. In the first days of life, the specific gravity of blood is higher (1060-1080 g/l) than in adults (1050-1060 g/l), but then reaches these values. The viscosity of blood in a newborn is 10-15 times higher than the viscosity of water, and in an adult - 5 times; Viscosity decreases to adult levels by 1 month. A newborn is characterized by the presence of metabolic acidosis (pH 7.13 - 6.23). However, already on days 3-5 the pH reaches the values of an adult (pH = 7.35-7.40). However, throughout childhood, the number of buffer bases is reduced, that is, compensated acidosis occurs. The content of blood proteins in a newborn reaches 51-56 g/l, which is significantly lower than in an adult (70-80 g/l), at 1 year - 65 g/l. the level of the “adult” state is observed at 3 years (70 g/l). the ratio of individual fractions, similar to the “adult” state, is observed from 2-3 years of age (newborns have a relatively high proportion of β-globulins that came to them from their mother).

· The influence of training load on the blood system

· White blood. Under the influence of educational load, in children aged 10-12 years, in most cases there is an increase in the number of leukocytes (on average by 24%). The observed reaction is apparently associated with redistribution mechanisms rather than enhanced hematopoiesis.

· Erythrocyte sedimentation reaction (ESR). In the majority of children in the first grades (7-11 years old), the ESR accelerates immediately after an educational load. Acceleration of ESR is observed mainly in children whose initial ESR values fluctuated within normal limits (up to 12 mm/hour). In children whose ESR was increased before the school load, its slowdown is observed by the end of the school day. In some children (28.2%), ESR did not change. Thus, the influence of study load on ESR largely depends on the initial values: high ESR slows down, slowed down speeds up.

· Blood viscosity. The nature of the change in relative blood viscosity under the influence of training load also depends on the initial values. In children with low initial blood viscosity, an increase is observed by the end of the school day (on average 3.7 before lessons and 5.0 after lessons). In those children whose viscosity was relatively high before classes (on average 4.4), after classes it clearly decreased (on average 3.4). In 50% of the children examined, blood viscosity increased as the number of red blood cells fell.

· Blood glucose level. During the school day, a change in glucose levels occurs in the blood of children aged 8-11 years. In this case, a certain dependence of the shift direction on the initial concentration is observed. In those children whose initial blood glucose level was 96 mg%, a decrease in concentration was observed after school (up to 79 mg% on average). In children with an initial blood glucose concentration of 81 mg% on average, its concentration increased to 97 mg%

· Blood clotting. Blood clotting sharply accelerated under the influence of educational load in most children 8-11 years old. However, there was no connection between the initial blood clotting time and the subsequent reaction.

· Influence physical activity on the blood system

· White blood. In general, the reaction of white blood to muscle work in adolescents and young men has the same patterns as in adults. When working at low power (playing, running), adolescents aged 14-17 years experience the first, lymphocytic, phase of myogenic leukocytosis. When working with high power (bicycle racing) - the neutrophilic, or second, phase of myogenic leukocytosis.

· After short-term muscular activity (running, swimming), boys and girls aged 16-18 years experience leukocytosis due to an increase in the concentration of almost all formed elements of white blood. However, the increase in the percentage and absolute content of lymphocytes predominates. There was no difference in the blood reaction of boys and girls to these loads.

· The severity of myogenic leukocytosis depends on the duration of muscle work: with increasing duration and power of work, leukocytosis intensifies.

· No age-related differences have been established in the nature of changes in white blood occurring after muscular activity. No significant differences were found when studying the period of restoration of the white blood picture in young (16-18 years old) and adults (23-27 years old) individuals. Both of them show signs of myogenic leukocytosis an hour and a half after intense work (50 km cycling race). Normalization of the blood picture, that is, restoration to the original values, occurred 24 hours after work. Simultaneously with leukocytosis, increased leukocytosis is observed. Maximum lysis of white blood cells was observed 3 hours after work. At the same time, in young men the intensity of leukocytolysis is slightly higher than in adults.

· Red blood. During short-term muscle strain (running, swimming), the amount of hemoglobin in boys and girls 16-18 years old changes slightly. The number of red blood cells in most cases increases slightly (maximum by 8-13%).

· After an intense duration of muscular activity (50 km cycling race), the amount of hemoglobin in most cases also remains virtually unchanged. The total number of red blood cells decreases (ranging from 220,000 to 1,100,000 per mm3 of blood). An hour and a half after a cycling race, the process of erythrocytolysis intensifies. After 24 hours, the number of red blood cells has not yet reached the initial level. Clearly expressed erythrocytolysis in the blood of young athletes is accompanied by an increase in young forms of erythrocytes - reticulocytes. Reticulocytosis persists in the blood for 24 hours. after work.

· Platelets. Muscular activity causes clearly defined thrombocytosis in people of all ages, which has been called myogenic. There are 2 phases of myogenic thrombocytosis. The first, usually occurring during short-term muscle activity, is expressed in an increase in the number of blood platelets without a shift in the thrombocytogram. This phase is associated with redistribution mechanisms. The second, which usually occurs with intense and prolonged muscle strain, is expressed not only in an increase in the number of platelets, but also in a shift in the platelet count towards younger forms. Age differences lie in the fact that with the same load, boys aged 16-18 years old exhibit a clearly expressed second phase of myogenic thrombocytosis. At the same time, in 40% of young men, the platelet blood count does not return to its original level 24 hours after work. In adults, the recovery period does not exceed 24 hours.

· Blood viscosity. The relative viscosity of blood in boys and girls aged 16-17 years does not change significantly after short-term work. After prolonged and intense muscle tension, blood viscosity clearly increases. The degree of change in blood viscosity depends on the duration of muscle work. When operating at high power and duration, changes in blood viscosity are protracted; recovery to the original value does not always occur even 24-40 hours after work.

· Blood clotting. The manifestation of a protective increase in blood coagulation during muscle activity has its own age-specific characteristics. Thus, after the same work, more pronounced thrombocytosis is observed in young men than in adults. Blood clotting time is shortened equally in adolescents 12-14 years old, in young men 16-18 years old, and in adults 23-27 years old. However, the period of restoration of the coagulation rate to the initial one is longer in adolescents and young men.

· circulatory psychophysiological teenager memory

Formed elements of blood

The formed elements of blood include: erythrocytes (or red blood cells), leukocytes (or white blood cells), and platelets (or platelets). A person has about 5 x 10 12 red blood cells in 1 liter of blood, leukocytes - about 6 x 10 9 (i.e. 1000 times less), and platelets - 2.5 x 10 11 in 1 liter of blood (i.e. 20 times less than red blood cells).

The population of blood cells is renewed, with a short development cycle, where most mature forms are terminal (dying) cells.

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

When blood cells precipitate in the presence of anticoagulants, a supernatant called plasma is produced. Plasma is an opalescent liquid containing all the extracellular components of blood [show] .

Most of the plasma contains sodium and chloride ions, therefore, in case of large blood losses, an isotonic solution containing 0.85% sodium chloride is injected into the veins to maintain heart function.

The red color of blood is given by red blood cells containing red respiratory pigment - hemoglobin, which absorbs oxygen in the lungs and releases it to the tissues. Blood saturated with oxygen is called arterial, and blood depleted of oxygen is called venous.

Normal blood volume averages 5200 ml in men and 3900 ml in women, or 7-8% of body weight. Plasma makes up 55% of blood volume and formed elements make up 44% of total blood volume, while other cells account for only about 1%.

If blood is allowed to clot and then the clot is separated, blood serum is obtained. Serum is the same plasma, devoid of fibrinogen, which is part of the blood clot.

According to its physicochemical properties, blood is a viscous liquid. The viscosity and density of blood depend on the relative content of blood cells and plasma proteins. Normally, the relative density of whole blood is 1.050-1.064, plasma - 1.024-1.030, cells - 1.080-1.097. The viscosity of blood is 4-5 times higher than the viscosity of water. Viscosity is important in maintaining blood pressure at a constant level.

Blood transporting in the body chemical substances, combines the biochemical processes occurring in different cells and intercellular spaces into a single system. Such a close relationship between blood and all tissues of the body allows us to maintain a relatively constant chemical composition blood due to powerful regulatory mechanisms (CNS, hormonal system etc.) ensuring a clear relationship in the work of such important organs and tissues as the liver, kidneys, lungs and cardiovascular system. All random fluctuations in the composition of the blood in a healthy body quickly level out.

In many pathological processes, more or less sharp changes are observed in the chemical composition of the blood, which signal disturbances in the state of human health, make it possible to monitor the development of the pathological process and judge the effectiveness of therapeutic measures.

[show]

Shaped elements	Cell structure	Place of education	Duration of operation	Place of death	Content in 1 mm 3 blood	Functions
Red blood cells	Red anucleate blood cells of a biconcave shape containing protein - hemoglobin	Red bone marrow	3-4 months	Spleen. Hemoglobin is broken down in the liver	4.5-5 million	Transfer of O 2 from lungs to tissues and CO 2 from tissues to lungs
Leukocytes	White blood amoeboid cells with a nucleus	Red bone marrow, spleen, lymph nodes	3-5 days	Liver, spleen, as well as places where the inflammatory process occurs	6-8 thousand	Protection of the body from pathogenic microbes by phagocytosis. Produce antibodies, creating immunity
Platelets	Nuclear-free blood cells	Red bone marrow	5-7 days	Spleen	300-400 thousand	Participate in blood clotting when a blood vessel is damaged, promoting the conversion of fibrinogen protein into fibrin - a fibrous blood clot

Erythrocytes, or red blood cells, are small (7-8 microns in diameter) anucleate cells, shaped like a biconcave disk. The absence of a nucleus allows the red blood cell to accommodate a large amount of hemoglobin, and its shape helps to increase its surface area. There are 4-5 million red blood cells in 1 mm 3 of blood. The number of red blood cells in the blood is not constant. It increases with increasing altitude, large losses of water, etc.

Throughout a person's life, red blood cells are formed from nucleated cells in the red bone marrow of the spongy bone. During the process of maturation, they lose their nucleus and enter the blood. The lifespan of human red blood cells is about 120 days, then they are destroyed in the liver and spleen and bile pigment is formed from hemoglobin.

The function of red blood cells is to transport oxygen and partially carbon dioxide. Red blood cells perform this function due to the presence of hemoglobin in them.

Hemoglobin is a red iron-containing pigment consisting of an iron porphyrin group (heme) and globin protein. 100 ml of human blood contains an average of 14 g of hemoglobin. In the pulmonary capillaries, hemoglobin, combining with oxygen, forms a fragile compound - oxidized hemoglobin (oxyhemoglobin) due to divalent heme iron. In the capillaries of tissues, hemoglobin gives up its oxygen and turns into reduced hemoglobin of a darker color, so venous blood flowing from tissues is dark red, and arterial blood, rich in oxygen, is scarlet.

Hemoglobin carries carbon dioxide from tissue capillaries to the lungs [show] .

Carbon dioxide formed in tissues enters red blood cells and, interacting with hemoglobin, is converted into carbonic acid salts - bicarbonates. This transformation occurs in several stages. Oxyhemoglobin in arterial blood erythrocytes is in the form of potassium salt - KHbO 2. In tissue capillaries, oxyhemoglobin gives up its oxygen and loses its acid properties; At the same time, carbon dioxide diffuses into the erythrocyte from the tissues through the blood plasma and, with the help of the enzyme present there - carbonic anhydrase - combines with water, forming carbonic acid - H 2 CO 3. The latter, as an acid stronger than reduced hemoglobin, reacts with its potassium salt, exchanging cations with it:

KHbO 2 → KHb + O 2; CO 2 + H 2 O → H + · NSO - 3;
KHb + H + · НСО — 3 → Н · Нb + K + · НСО — 3 ;

The potassium bicarbonate formed as a result of the reaction dissociates and its anion, due to its high concentration in the erythrocyte and the permeability of the erythrocyte membrane to it, diffuses from the cell into the plasma. The resulting lack of anions in the erythrocyte is compensated by chlorine ions, which diffuse from the plasma into the erythrocytes. In this case, a dissociated sodium salt of bicarbonate is formed in the plasma, and the same dissociated potassium chloride salt is formed in the erythrocyte:

Note that the erythrocyte membrane is impermeable to K and Na cations and that the diffusion of HCO - 3 from the erythrocyte occurs only until its concentration in the erythrocyte and plasma is equalized.

In the capillaries of the lungs, these processes go in the opposite direction:

H Hb + O 2 → H Hb0 2;
H HbO 2 + K HCO 3 → H HCO 3 + K HbO 2.

The resulting carbonic acid is broken down by the same enzyme to H 2 O and CO 2, but as the HCO 3 content in the erythrocyte decreases, these anions from the plasma diffuse into it, and the corresponding amount of Cl anions leaves the erythrocyte into the plasma. Consequently, oxygen in the blood is bound to hemoglobin, and carbon dioxide exists in the form of bicarbonate salts.

100 ml of arterial blood contains 20 ml of oxygen and 40-50 ml of carbon dioxide, venous blood contains 12 ml of oxygen and 45-55 ml of carbon dioxide. Only a very small proportion of these gases are directly dissolved in blood plasma. The bulk of blood gases, as can be seen from the above, are in a chemically bound form. With a reduced number of red blood cells in the blood or hemoglobin in red blood cells, a person develops anemia: the blood is poorly saturated with oxygen, so organs and tissues receive insufficient amounts of it (hypoxia).

Leukocytes, or white blood cells, - colorless blood cells with a diameter of 8-30 microns, of variable shape, having a nucleus; The normal number of leukocytes in the blood is 6-8 thousand per 1 mm3. Leukocytes are formed in the red bone marrow, liver, spleen, lymph nodes; their lifespan can vary from several hours (neutrophils) to 100-200 or more days (lymphocytes). They are also destroyed in the spleen.

Based on their structure, leukocytes are divided into several [the link is available to registered users who have 15 messages on the forum], each of which performs specific functions. The percentage of these groups of leukocytes in the blood is called the leukocyte formula.

The main function of leukocytes is to protect the body from bacteria, foreign proteins, and foreign bodies. [show] .

By modern views body protection, i.e. its immunity to various factors that carry genetically foreign information is ensured by immunity, represented by a variety of cells: leukocytes, lymphocytes, macrophages, etc., thanks to which foreign cells or complex organic substances that enter the body, different from the cells and substances of the body, are destroyed and eliminated .

Immunity maintains the genetic constancy of the organism in ontogenesis. When cells divide as a result of mutations in the body, cells with an altered genome are often formed. To ensure that these mutant cells during further division do not lead to disturbances in the development of organs and tissues, they are destroyed by the body’s immune systems. In addition, immunity is manifested in the body's immunity to transplanted organs and tissues from other organisms.

The first scientific explanation of the nature of immunity was given by I. I. Mechnikov, who came to the conclusion that immunity is provided due to the phagocytic properties of leukocytes. Later it was found that, in addition to phagocytosis (cellular immunity), great importance for immunity, leukocytes have the ability to produce protective substances - antibodies, which are soluble protein substances - immunoglobulins (humoral immunity), produced in response to the appearance of foreign proteins in the body. 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 certain infectious diseases.

There are innate and acquired immunity. The first provides immunity to a particular infectious disease from the moment of birth and is inherited from parents, and 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 appears after suffering an infectious disease, when antibodies are formed in the blood plasma in response to foreign proteins of a given microorganism. In this case, natural, acquired immunity occurs.

Immunity can be developed artificially by introducing weakened or killed pathogens of a disease into the human body (for example, smallpox vaccination). This immunity does not occur immediately. For its manifestation, time is required for the body to produce antibodies against the introduced weakened microorganism. Such immunity usually lasts for years and is called active.

The world's first vaccination against smallpox was carried out by the English doctor E. Jenner.

Immunity acquired by introducing immune serum from the blood of animals or humans into the body is called passive (for example, anti-measles serum). It appears immediately after the administration of the serum, persists for 4-6 weeks, and then the antibodies are gradually destroyed, immunity weakens, and repeated administration of the immune serum is necessary to maintain it.

The ability of leukocytes to move independently with the help of pseudopods allows them, making amoeboid movements, to penetrate through the walls of capillaries into the intercellular spaces. 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 into the cell, where they are broken down with the participation of enzymes (intracellular digestion). In the process of interaction with foreign bodies many leukocytes die. In this case, decay products accumulate around the foreign body and pus is formed.

This phenomenon was discovered by I.I. Mechnikov. I. I. Mechnikov called leukocytes that capture various microorganisms and digest them phagocytes, and the phenomenon of absorption and digestion itself was called phagocytosis. Phagocytosis is a protective reaction of the body.

Mechnikov Ilya Ilyich(1845-1916) - Russian evolutionary biologist. One of the founders of comparative embryology, comparative pathology, microbiology.

He proposed an original theory of the origin of multicellular animals, which is called the theory of phagocytella (parenchymella). Discovered the phenomenon of phagocytosis. Developed problems of immunity.

Founded in Odessa, together with N. F. Gamaleya, the first bacteriological station in Russia (currently the I. I. Mechnikov Research Institute). Recipient of two awards: K.M. Baer in embryology and the Nobel Prize for the discovery of the phenomenon of phagocytosis. He devoted the last years of his life to studying the problem of longevity.

The phagocytic ability of leukocytes is extremely important because it protects the body from infection. But in certain cases, this property of white blood cells can be harmful, for example during organ transplantation. Leukocytes react to transplanted organs in the same way as to pathogens, - phagocytize and destroy them. To avoid an undesirable reaction of leukocytes, phagocytosis is inhibited with special substances.

Platelets, or blood platelets, - colorless cells 2-4 microns in size, the number of which is 200-400 thousand in 1 mm 3 of blood. They are formed in the bone marrow. Platelets are very fragile and are easily destroyed when blood vessels are damaged or when blood comes into contact with air. At the same time, a special substance thromboplastin is released from them, which promotes blood clotting.

Blood plasma proteins

Of the 9-10% of the dry residue of blood plasma, proteins account for 6.5-8.5%. Using the method of salting out with neutral salts, blood plasma proteins can be divided into three groups: albumins, globulins, fibrinogen. The normal content of albumin in blood plasma is 40-50 g/l, globulin - 20-30 g/l, fibrinogen - 2-4 g/l. Blood plasma devoid of fibrinogen is called serum.

The synthesis of blood plasma proteins occurs primarily in the cells of the liver and reticuloendothelial system. The physiological role of blood plasma proteins is multifaceted.

Modern physicochemical research methods have made it possible to discover and describe about 100 different protein components of blood plasma. At the same time, the electrophoretic separation of blood plasma (serum) proteins has acquired particular importance. [show] .

In the blood serum of a healthy person, electrophoresis on paper can detect five fractions: albumin, α 1, α 2, β- and γ-globulins (Fig. 125). By electrophoresis in agar gel, up to 7-8 fractions are detected in blood serum, and by electrophoresis in starch or polyacrylamide gel - up to 16-17 fractions.

It should be remembered that the terminology of protein fractions obtained by various types electrophoresis, has not yet been completely established. When changing electrophoresis conditions, as well as during electrophoresis in different media (for example, in starch or polyacrylamide gel), the migration rate and, consequently, the order of protein zones can change.

An even larger number of protein fractions (about 30) can be obtained using the immunoelectrophoresis method. Immunoelectrophoresis is a unique combination of electrophoretic and immunological methods protein analysis. In other words, the term “immunoelectrophoresis” means carrying out electrophoresis and precipitation reactions in the same medium, i.e. directly on the gel block. With this method, using a serological precipitation reaction, a significant increase in the analytical sensitivity of the electrophoretic method is achieved. In Fig. 126 shows a typical immunoelectropherogram of human serum proteins.

Characteristics of the main protein fractions

Albumin [show] .
Albumin accounts for more than half (55-60%) of human blood plasma proteins. The molecular weight of albumin is about 70,000. Serum albumin is renewed relatively quickly (the half-life of human albumin is 7 days).
Due to their high hydrophilicity, especially due to the relatively small size of the molecules and significant concentration in the serum, albumins play an important role in maintaining the colloid osmotic pressure of the blood. It is known that serum albumin concentrations below 30 g/l cause significant changes in blood oncotic pressure, which leads to edema. Albumins perform an important function in transporting many biologically active substances (in particular, hormones). They are able to bind to cholesterol and bile pigments. A significant portion of serum calcium is also bound to albumin.
When electrophoresis in starch gel, the albumin fraction in some people is sometimes divided into two (albumin A and albumin B), i.e., such people have two independent genetic loci that control albumin synthesis. The additional fraction (albumin B) differs from regular serum albumin in that the molecules of this protein contain two or more dicarboxylic amino acid residues that replace tyrosine or cystine residues in the polypeptide chain of regular albumin. There are other rare variants of albumin (Reading albumin, Gent albumin, Maki albumin). Inheritance of albumin polymorphism occurs in an autosomal codominant manner and is observed over several generations.
In addition to hereditary albumin polymorphism, transient bisalbuminemia occurs, which in some cases can be mistaken for congenital. The appearance of a fast component of albumin in patients receiving large doses of penicillin has been described. After discontinuation of penicillin, this fast component of albumin soon disappeared from the blood. There is an assumption that the increase in the electrophoretic mobility of the albumin-antibiotic fraction is associated with an increase in the negative charge of the complex due to the COOH groups of penicillin.
Globulins [show] .
When salted out with neutral salts, serum globulins can be divided into two fractions - euglobulins and pseudoglobulins. It is believed that the euglobulin fraction mainly consists of γ-globulins, and the pseudoglobulin fraction includes α-, β- and γ-globulins.
α-, β- and γ-globulins are heterogeneous fractions that, during electrophoresis, especially in starch or polyacrylamide gels, can be separated into a number of subfractions. It is known that α- and β-globulin fractions contain lipoproteins and glycoproteins. Among the components of α- and β-globulins there are also metal-bound proteins. Most of the antibodies contained in serum are in the γ-globulin fraction. A decrease in the protein content of this fraction sharply reduces the body's defenses.

IN clinical practice There are conditions characterized by changes in both the total amount of blood plasma proteins and the percentage of individual protein fractions.

As noted, α- and β-globulin fractions of serum proteins contain lipoproteins and glycoproteins. The carbohydrate part of blood glycoproteins mainly includes the following monosaccharides and their derivatives: galactose, mannose, fucose, rhamnose, glucosamine, galactosamine, neuraminic acid and its derivatives (sialic acids). The ratio of these carbohydrate components in individual serum glycoproteins is different.

Most often, aspartic acid (its carboxyl) and glucosamine take part in the connection between the protein and carbohydrate parts of the glycoprotein molecule. Somewhat less common is the connection between the hydroxyl of threonine or serine and hexosamines or hexoses.

Neuramic acid and its derivatives (sialic acids) are the most labile and active components of glycoproteins. They occupy the final position in the carbohydrate chain of the glycoprotein molecule and largely determine the properties of this glycoprotein.

Glycoproteins are present in almost all protein fractions of blood serum. When electrophoresis on paper, glycoproteins are detected in greater quantities in the α 1 - and α 2 -fractions of globulins. Glycoproteins associated with α-globulin fractions contain little fucose; at the same time, glycoproteins detected in the β- and especially γ-globulin fractions contain significant amounts of fucose.

An increased content of glycoproteins in plasma or serum is observed in tuberculosis, pleurisy, pneumonia, acute rheumatism, glomerulonephritis, nephrotic syndrome, diabetes, myocardial infarction, gout, as well as in acute and chronic leukemia, myeloma, lymphosarcoma and some other diseases. In patients with rheumatism, an increase in the content of glycoproteins in the serum corresponds to the severity of the disease. This is explained, according to a number of researchers, by depolymerization of the main substance of connective tissue during rheumatism, which leads to the entry of glycoproteins into the blood.

Plasma lipoproteins- these are complex complex compounds with a characteristic structure: inside the lipoprotein particle there is a fat drop (core) containing non-polar lipids (triglycerides, esterified cholesterol). The fat droplet is surrounded by a membrane that contains phospholipids, protein and free cholesterol. The main function of plasma lipoproteins is the transport of lipids in the body.

Several classes of lipoproteins have been found in human blood plasma.

α-lipoproteins, or high-density lipoproteins (HDL). During electrophoresis on paper, they migrate together with α-globulins. HDL is rich in protein and phospholipids, and is constantly found in the blood plasma of healthy people at a concentration of 1.25-4.25 g/l in men and 2.5-6.5 g/l in women.
β-lipoproteins, or low-density lipoproteins (LDL). They correspond in electrophoretic mobility to β-globulins. They are the most cholesterol-rich class of lipoproteins. The level of LDL in the blood plasma of healthy people is 3.0-4.5 g/l.
pre-β-lipoproteins, or very low density lipoproteins (VLDL). Located on the lipoproteinogram between α- and β-lipoproteins (electrophoresis on paper), they serve as the main transport form of endogenous triglycerides.
Chylomicrons (CM). They do not move during electrophoresis either to the cathode or to the anode and remain at the start (the place where the test plasma or serum sample is applied). They are formed in the intestinal wall during the absorption of exogenous triglycerides and cholesterol. First, chemical substances enter the thoracic lymphatic duct, and from it into the bloodstream. ChMs are the main transport form of exogenous triglycerides. The blood plasma of healthy people who have not eaten for 12-14 hours does not contain CM.

It is believed that the main place of formation of plasma pre-β-lipoproteins and α-lipoproteins is the liver, and β-lipoproteins are formed from pre-β-lipoproteins in the blood plasma under the action of lipoprotein lipase.

It should be noted that electrophoresis of lipoproteins can be carried out both on paper and in agar, starch and polyacrylamide gels, cellulose acetate. When choosing an electrophoresis method, the main criterion is to clearly obtain four types of lipoproteins. Electrophoresis of lipoproteins in polyacrylamide gel is currently the most promising. In this case, the fraction of pre-β-lipoproteins is detected between CM and β-lipoproteins.

In a number of diseases, the lipoprotein spectrum of blood serum may change.

According to the existing classification of hyperlipoproteinemia, the following five types of deviation of the lipoprotein spectrum from the norm have been established [show] .

Type I - hyperchylomicronemia. The main changes in the lipoproteinogram are as follows: high content of CM, normal or slightly increased content pre-β-lipoproteins. Sharp increase serum triglyceride levels. Clinically, this condition manifests itself as xanthomatosis.
Type II - hyper-β-lipoproteinemia. This type is divided into two subtypes:
- IIa, characterized by a high level of p-lipoproteins (LDL) in the blood,
- IIb, characterized by a high content of two classes of lipoproteins simultaneously - β-lipoproteins (LDL) and pre-β-lipoproteins (VLDL).
In type II, there is a high, and in some cases very high, cholesterol content in the blood plasma. The content of triglycerides in the blood can be either normal (type IIa) or elevated (type IIb). Type II is clinically manifested by atherosclerotic disorders, and coronary heart disease often develops.
Type III - “floating” hyperlipoproteinemia or dys-β-lipoproteinemia. Lipoproteins with an unusually high cholesterol content and high electrophoretic mobility (“pathological” or “floating” β-lipoproteins) appear in the blood serum. They accumulate in the blood due to a violation of the conversion of pre-β-lipoproteins into β-lipoproteins. This type of hyperlipoproteinemia is often combined with various manifestations of atherosclerosis, including coronary heart disease and damage to the blood vessels of the legs.
Type IV - hyperpre-β-lipoproteinemia. Increased levels of pre-β-lipoproteins, normal levels of β-lipoproteins, absence of CM. Increased triglyceride levels with normal or slightly elevated level cholesterol. Clinically, this type is combined with diabetes, obesity, and coronary heart disease.
Type V - hyperpre-β-lipoproteinemia and chylomicronemia. There is an increase in the level of pre-β-lipoproteins and the presence of CM. Clinically manifested by xanthomatosis, sometimes combined with latent diabetes. Coronary disease heart disease is not observed in this type of hyperlipoproteinemia.

Some of the most studied and clinically interesting plasma proteins

Immunoglobulins [show] .

Until recently, four main classes of immunoglobulins included in the γ-globulin fraction were known: IgG, IgM, IgA and IgD. IN last years The fifth class of immunoglobulins, IgE, was discovered. Immunoglobulins practically have a single structure plan; they consist of two heavy polypeptide chains H (mol. wt 50,000-75,000) and two light chains L (mol. wt ~ 23,000), connected by three disulfide bridges. In this case, human immunoglobulins can contain two types of L chains (K or λ). In addition, each class of immunoglobulins has its own type of heavy chain H: IgG - γ-chain, IgA - α-chain, IgM - μ-chain, IgD - σ-chain and IgE - ε-chain, which differ in amino acid composition. IgA and IgM are oligomers, i.e. the four-chain structure in them is repeated several times.

Each type of immunoglobulin can specifically interact with a specific antigen. The term "immunoglobulins" refers not only to normal classes of antibodies, but also to a larger number of so-called pathological proteins, for example myeloma proteins, the increased synthesis of which occurs in multiple myeloma. As already noted, in the blood of this disease, myeloma proteins accumulate in relatively high concentrations, and Bence-Jones protein is found in the urine. It turned out that Bence-Jones protein consists of L-chains, which are apparently synthesized in the patient's body in excess quantities compared to H-chains and are therefore excreted in the urine. The C-terminal half of the polypeptide chain of Bence-Jones protein molecules (actually L-chains) in all patients with multiple myeloma has the same sequence, and the N-terminal half (107 amino acid residues) of the L-chains has a different primary structure. A study of the N-chains of myeloma blood plasma proteins also revealed an important pattern: the N-terminal fragments of these chains in different patients have different primary structures, while the rest of the chain remains unchanged. It was concluded that the variable regions of the L- and H-chains of immunoglobulins are the site of specific binding of antigens.

In many pathological processes, the content of immunoglobulins in blood serum changes significantly. Thus, with chronic aggressive hepatitis there is an increase in IgG, with alcoholic cirrhosis - IgA and with primary biliary cirrhosis - IgM. It has been shown that the concentration of IgE in the blood serum increases with bronchial asthma, nonspecific eczema, ascariasis and some other diseases. It is important to note that children who have IgA deficiency are more likely to develop infectious diseases. It can be assumed that this is a consequence of insufficient synthesis of a certain part of the antibodies.

Complement system

The complement system of human blood serum includes 11 proteins with a molecular weight from 79,000 to 400,000. The cascade mechanism of their activation is triggered during the reaction (interaction) of an antigen with an antibody:

As a result of the action of complement, the destruction of cells through their lysis, as well as the activation of leukocytes and their absorption of foreign cells as a result of phagocytosis are observed.

According to the sequence of functioning, proteins of the human serum complement system can be divided into three groups:

“recognition group”, which includes three proteins and binds the antibody on the surface of the target cell (this process is accompanied by the release of two peptides);
both peptides on another part of the surface of the target cell interact with three proteins of the “activating group” of the complement system, and two peptides are also formed;
newly isolated peptides contribute to the formation of a group of “membrane attack” proteins, consisting of 5 proteins of the complement system, cooperatively interacting with each other on the third area of the surface of the target cell. The binding of membrane attack proteins to the cell surface destroys it by forming end-to-end channels in the membrane.

Blood plasma (serum) enzymes

Enzymes that are normally found in plasma or serum can, however somewhat arbitrarily, be divided into three groups:

Secretory - synthesized in the liver, they are normally released into the blood plasma, where they play a certain physiological role. Typical representatives of this group are enzymes involved in the process of blood clotting (see p. 639). Serum cholinesterase belongs to this group.
Indicator (cellular) enzymes perform certain intracellular functions in tissues. Some of them are concentrated mainly in the cytoplasm of the cell (lactate dehydrogenase, aldolase), others - in mitochondria (glutamate dehydrogenase), others - in lysosomes (β-glucuronidase, acid phosphatase), etc. Most of the indicator enzymes in blood serum are determined only in trace amounts. When certain tissues are damaged, the activity of many indicator enzymes increases sharply in the blood serum.
Excretory enzymes are synthesized mainly in the liver (leucine aminopeptidase, alkaline phosphatase, etc.). Under physiological conditions, these enzymes are mainly excreted in bile. The mechanisms regulating the entry of these enzymes into bile capillaries have not yet been fully elucidated. In many pathological processes, the release of these enzymes with bile is disrupted and the activity of excretory enzymes in the blood plasma increases.

Of particular clinical interest is the study of the activity of indicator enzymes in blood serum, since the appearance of a number of tissue enzymes in unusual quantities in plasma or serum can indicate the functional state and disease of various organs (for example, liver, cardiac and skeletal muscles).

Thus, from the point of view of diagnostic value, studies of enzyme activity in blood serum during acute myocardial infarction can be compared with the electrocardiographic diagnostic method introduced several decades ago. Determination of enzyme activity during myocardial infarction is advisable in cases where the course of the disease and electrocardiographic data are atypical. In acute myocardial infarction, it is especially important to study the activity of creatine kinase, aspartate aminotransferase, lactate dehydrogenase and hydroxybutyrate dehydrogenase.

In case of liver diseases, in particular with viral hepatitis (Botkin's disease), the activity of alanine and aspartate aminotransferases, sorbitol dehydrogenase, glutamate dehydrogenase and some other enzymes in the blood serum changes significantly, and the activity of histidase and urocaninase appears. Most of the enzymes contained in the liver are also present in other organs and tissues. However, there are enzymes that are more or less specific to liver tissue. Organ-specific enzymes for the liver are: histidase, urocaninase, ketose-1-phosphate aldolase, sorbitol dehydrogenase; ornithine carbamoyltransferase and, to a slightly lesser extent, glutamate dehydrogenase. Changes in the activity of these enzymes in the blood serum indicate damage to the liver tissue.

In the last decade, the study of isoenzyme activity in blood serum, in particular lactate dehydrogenase isoenzymes, has become a particularly important laboratory test.

It is known that in the heart muscle the isoenzymes LDH 1 and LDH 2 are most active, and in the liver tissue - LDH 4 and LDH 5. It has been established that in patients with acute myocardial infarction the activity of isoenzymes LDH 1 and partly LDH 2 sharply increases in the blood serum. The isoenzyme spectrum of lactate dehydrogenase in blood serum during myocardial infarction resembles the isoenzyme spectrum of the heart muscle. On the contrary, with parenchymal hepatitis in the blood serum the activity of the isoenzymes LDH 5 and LDH 4 increases significantly and the activity of LDH 1 and LDH 2 decreases.

The study of the activity of creatine kinase isoenzymes in blood serum is also of diagnostic importance. There are at least three creatine kinase isoenzymes: BB, MM and MB. The BB isoenzyme is mainly present in brain tissue, and the MM form is present in skeletal muscles. The heart contains predominantly the MM form, as well as the MV form.

Creatine kinase isoenzymes are especially important to study in acute myocardial infarction, since the MB form is found in significant quantities almost only in the heart muscle. Therefore, an increase in the activity of the MB form in the blood serum indicates damage to the heart muscle. Apparently, the increase in enzyme activity in the blood serum in many pathological processes is explained by at least two reasons: 1) the release of enzymes into the bloodstream from damaged areas of organs or tissues against the background of their ongoing biosynthesis in damaged tissues and 2) a simultaneous sharp increase in catalytic activity tissue enzymes that pass into the blood.

It is possible that a sharp increase in enzyme activity when the mechanisms of intracellular regulation of metabolism break down is associated with the cessation of the action of the corresponding enzyme inhibitors, a change under the influence of various factors in the secondary, tertiary and quaternary structures of enzyme macromolecules, which determine their catalytic activity.

Non-protein nitrogenous components of blood

The content of non-protein nitrogen in whole blood and plasma is almost the same and is 15-25 mmol/l in the blood. Non-protein nitrogen in the blood includes urea nitrogen (50% of the total amount of non-protein nitrogen), amino acids (25%), ergothioneine - a compound found in red blood cells (8%), uric acid (4%), creatine (5%), creatinine ( 2.5%), ammonia and indican (0.5%) and other non-protein substances containing nitrogen (polypeptides, nucleotides, nucleosides, glutathione, bilirubin, choline, histamine, etc.). Thus, the composition of non-protein nitrogen in the blood consists mainly of nitrogen final products exchange of simple and complex proteins.

Non-protein nitrogen in the blood is also called residual nitrogen, that is, remaining in the filtrate after precipitation of proteins. In a healthy person, fluctuations in the content of non-protein, or residual, blood nitrogen are insignificant and mainly depend on the amount of protein ingested from food. In a number of pathological conditions, the level of non-protein nitrogen in the blood increases. This condition is called azotemia. Azotemia, depending on the reasons that caused it, is divided into retention and production. Retention azotemia occurs as a result of insufficient excretion of nitrogen-containing products in the urine during their normal entry into the bloodstream. It, in turn, can be renal or extrarenal.

With renal retention azotemia, the concentration of residual nitrogen in the blood increases due to a weakening of the cleansing (excretory) function of the kidneys. A sharp increase in the content of residual nitrogen during retention renal azotemia occurs mainly due to urea. In these cases, urea nitrogen accounts for 90% of the non-protein nitrogen in the blood instead of 50% normally. Extrarenal retention azotemia may result from severe circulatory failure, decreased blood pressure, and decreased renal blood flow. Often, extrarenal retention azotemia is the result of an obstruction to the outflow of urine after its formation in the kidney.

Table 46. Content of free amino acids in human blood plasma
Amino acids	Content, µmol/l
Alanin	360-630
Arginine	92-172
Asparagine	50-150
Aspartic acid	150-400
Valin	188-274
Glutamic acid	54-175
Glutamine	514-568
Glycine	100-400
Histidine	110-135
Isoleucine	122-153
Leucine	130-252
Lysine	144-363
Methionine	20-34
Ornithine	30-100
Proline	50-200
Serin	110
Threonine	160-176
Tryptophan	49
Tyrosine	78-83
Phenylalanine	85-115
Citrulline	10-50
Cystine	84-125

Productive azotemia observed when there is an excessive intake of nitrogen-containing products into the blood, as a result of increased breakdown of tissue proteins. Mixed azotemia is often observed.

As already noted, in terms of quantity, the main end product of protein metabolism in the body is urea. It is generally accepted that urea is 18 times less toxic than other nitrogenous substances. In acute renal failure, the concentration of urea in the blood reaches 50-83 mmol/l (normal 3.3-6.6 mmol/l). An increase in the urea content in the blood to 16.6-20.0 mmol/l (calculated on urea nitrogen [The value of the urea nitrogen content is approximately 2 times, or more precisely 2.14 times less than the number expressing the concentration of urea.]) is a sign renal dysfunction moderate severity, up to 33.3 mmol/l - severe and over 50 mmol/l - very severe disorder with a poor prognosis. Sometimes a special coefficient is determined or, more precisely, the ratio of blood urea nitrogen to residual blood nitrogen, expressed as a percentage: (Urea Nitrogen / Residual Nitrogen) X 100

Normally the ratio is below 48%. With renal failure, this figure increases and can reach 90%, and if the urea-forming function of the liver is impaired, the coefficient decreases (below 45%).

Uric acid is also an important protein-free nitrogenous substance in the blood. Let us recall that in humans, uric acid is the end product of the metabolism of purine bases. Normally, the concentration of uric acid in whole blood is 0.18-0.24 mmol/l (in serum - about 0.29 mmol/l). An increase in uric acid in the blood (hyperuricemia) is the main symptom of gout. With gout, the level of uric acid in the blood serum increases to 0.47-0.89 mmol/l and even to 1.1 mmol/l; The residual nitrogen also includes nitrogen from amino acids and polypeptides.

The blood always contains a certain amount of free amino acids. Some of them are of exogenous origin, i.e. they enter the blood from gastrointestinal tract, the other part of the amino acids is formed as a result of the breakdown of tissue proteins. Almost a fifth of the amino acids contained in plasma are glutamic acid and glutamine (Table 46). Naturally, the blood contains aspartic acid, asparagine, cysteine, and many other amino acids that are part of natural proteins. The content of free amino acids in serum and blood plasma is almost the same, but differs from their level in erythrocytes. Normally, the ratio of the amino acid nitrogen concentration in erythrocytes to the amino acid nitrogen content in plasma ranges from 1.52 to 1.82. This ratio (coefficient) is characterized by great constancy, and only in some diseases is its deviation from the norm observed.

Total determination of the level of polypeptides in the blood is performed relatively rarely. However, it should be remembered that many of the blood polypeptides are biologically active compounds and their determination is of great clinical interest. Such compounds, in particular, include kinins.

Kinins and blood kinin system

Kinins are sometimes called kinin hormones, or local hormones. They are not produced in specific endocrine glands, but are released from inactive precursors that are constantly present in the interstitial fluid of a number of tissues and in the blood plasma. Kinins are characterized by a wide range of biological effects. This action is mainly aimed at the smooth muscles of blood vessels and the capillary membrane; hypotensive effect is one of the main manifestations of the biological activity of kinins.

The most important plasma kinins are bradykinin, kallidin and methionyl-lysyl-bradykinin. In fact, they form a kinin system, which ensures the regulation of local and general blood flow and the permeability of the vascular wall.

The structure of these kinins has been fully established. Bradykinin is a polypeptide of 9 amino acids, kallidin (lysyl-bradykinin) is a polypeptide of 10 amino acids.

In blood plasma, the content of kinins is usually very low (for example, bradykinin 1-18 nmol/l). The substrate from which kinins are released is called kininogen. There are several kininogens in the blood plasma (at least three). Kininogens are proteins associated in the blood plasma with the α 2 -globulin fraction. The site of kininogen synthesis is the liver.

The formation (cleavage) of kinins from kininogens occurs with the participation of specific enzymes - kininogenases, which are called kallikreins (see diagram). Kallikreins are trypsin-type proteinases; they break peptide bonds in the formation of which the NOOS groups of arginine or lysine are involved; Proteolysis of proteins in a broad sense is not characteristic of these enzymes.

There are blood plasma kallikreins and tissue kallikreins. One of the kallikrein inhibitors is a polyvalent inhibitor isolated from the lungs and salivary gland of a bovine, known as trasylol. It is also a trypsin inhibitor and is used therapeutically for acute pancreatitis.

Part of bradykinin can be formed from kallidin as a result of cleavage of lysine with the participation of aminopeptidases.

In blood plasma and tissues, kallikreins are found mainly in the form of their precursors - kallikreinogens. It has been proven that the direct activator of kallikreinogen in blood plasma is the Hageman factor (see p. 641).

Kinins have a short-term effect in the body; they are quickly inactivated. This is explained by the high activity of kininases - enzymes that inactivate kinins. Kininases are found in blood plasma and almost all tissues. It is the high activity of kininases in blood plasma and tissues that determines the local nature of the action of kinins.

As already noted, the physiological role of the kinin system is reduced mainly to the regulation of hemodynamics. Bradykinin is the most powerful vasodilator. Kinins act directly on vascular smooth muscle, causing it to relax. They also actively influence capillary permeability. Bradykinin in this regard is 10-15 times more active than histamine.

There is evidence that bradykinin, by increasing vascular permeability, promotes the development of atherosclerosis. A close connection between the kinin system and the pathogenesis of inflammation has been established. It is possible that the kinin system plays an important role in the pathogenesis of rheumatism, and healing effect salicylates are explained by inhibition of bradykinin formation. Vascular abnormalities characteristic of shock are also likely associated with shifts in the kinin system. The participation of kinins in the pathogenesis of acute pancreatitis is also known.

An interesting feature of kinins is their bronchoconstrictor effect. It has been shown that the activity of kininases in the blood of asthma sufferers is sharply reduced, which creates favorable conditions for the manifestation of the action of bradykinin. There is no doubt that research into the role of the kinin system in bronchial asthma is very promising.

Nitrogen-free organic blood components

The group of nitrogen-free organic substances in the blood includes carbohydrates, fats, lipoids, organic acids and some other substances. All these compounds are either products of intermediate metabolism of carbohydrates and fats, or play the role of nutrients. Basic data characterizing the content of various nitrogen-free organic substances in the blood are presented in table. 43. In the clinic, great importance is attached to the quantitative determination of these components in the blood.

Electrolyte composition of blood plasma

It is known that the total water content in the human body is 60-65% of body weight, i.e. approximately 40-45 l (if body weight is 70 kg); 2/3 of the total amount of water is intracellular fluid, 1/3 is extracellular fluid. Part of the extracellular water is in the vascular bed (5% of body weight), while the majority is outside the vascular bed - this is interstitial, or tissue, fluid (15% of body weight). In addition, a distinction is made between “free water”, which forms the basis of intra- and extracellular fluids, and water associated with colloids (“bound water”).

The distribution of electrolytes in body fluids is very specific in its quantitative and qualitative composition.

Of the plasma cations, sodium occupies a leading place and makes up 93% of their total quantity. Among the anions, chlorine should be distinguished first, followed by bicarbonate. The sum of anions and cations is almost the same, i.e. the entire system is electrically neutral.

Tab. 47. Ratios of concentrations of hydrogen and hydroxyl ions and pH values (according to Mitchell, 1975)
H+	pH value	OH-
10 0 or 1.0	0,0	10 -14 or 0.00000000000001
10 -1 or 0.1	1,0	10 -13 or 0.0000000000001
10 -2 or 0.01	2,0	10 -12 or 0.000000000001
10 -3 or 0.001	3,0	10 -11 or 0.00000000001
10 -4 or 0.0001	4,0	10 -10 or 0.0000000001
10 -5 or 0.00001	5,0	10 -9 or 0.000000001
10 -6 or 0.000001	6,0	10 -8 or 0.00000001
10 -7 or 0.0000001	7,0	10 -7 or 0.0000001
10 -8 or 0.00000001	8,0	10 -6 or 0.000001
10 -9 or 0.000000001	9,0	10 -5 or 0.00001
10 -10 or 0.0000000001	10,0	10 -4 or 0.0001
10 -11 or 0.00000000001	11,0	10 -3 or 0.001
10 -12 or 0.000000000001	12,0	10 -2 or 0.01
10 -13 or 0.0000000000001	13,0	10 -1 or 0.1
10 -14 or 0.00000000000001	14,0	10 0 or 1.0

Sodium [show] .
Sodium is the main osmotically active ion in the extracellular space. In blood plasma, the concentration of Na + is approximately 8 times higher (132-150 mmol/l) than in erythrocytes (17-20 mmol/l).
With hypernatremia, as a rule, a syndrome associated with overhydration of the body develops. Accumulation of sodium in blood plasma is observed when special disease kidneys, so-called parenchymal nephritis, in patients with congenital heart failure, with primary and secondary hyperaldosteronism.
Hyponatremia is accompanied by dehydration of the body. Correction of sodium metabolism is carried out by introducing sodium chloride solutions with the calculation of its deficiency in the extracellular space and cell.
Potassium [show] .
Plasma K+ concentration ranges from 3.8 to 5.4 mmol/L; in erythrocytes it is approximately 20 times more (up to 115 mmol/l). The level of potassium in cells is much higher than in the extracellular space, therefore, in diseases accompanied by increased cellular breakdown or hemolysis, the potassium content in the blood serum increases.
Hyperkalemia is observed in acute renal failure and hypofunction of the adrenal cortex. Lack of aldosterone leads to increased urinary excretion of sodium and water and retention of potassium in the body.
On the contrary, with increased production of aldosterone by the adrenal cortex, hypokalemia occurs. At the same time, the excretion of potassium in the urine increases, which is combined with sodium retention in the tissues. Developing hypokalemia causes severe disturbances in the functioning of the heart, as evidenced by ECG data. A decrease in serum potassium is sometimes observed when large doses of adrenal hormones are administered for therapeutic purposes.
Calcium [show] .
Traces of calcium are found in erythrocytes, while in plasma its content is 2.25-2.80 mmol/l.
There are several fractions of calcium: ionized calcium, non-ionized calcium, but capable of dialysis, and non-dialyzable (non-diffusing) protein-bound calcium.
Calcium takes an active part in the processes of neuromuscular excitability as an antagonist of K +, muscle contraction, blood clotting, forms the structural basis of the bone skeleton, affects the permeability of cell membranes, etc.
A distinct increase in the level of calcium in the blood plasma is observed with the development of tumors in the bones, hyperplasia or adenoma of the parathyroid glands. In these cases, calcium comes into the plasma from the bones, which become brittle.
Important diagnostic value has a calcium determination for hypocalcemia. The state of hypocalcemia is observed in hypoparathyroidism. Loss of function of the parathyroid glands leads to a sharp decrease in the content of ionized calcium in the blood, which may be accompanied by convulsive attacks (tetany). A decrease in plasma calcium concentration is also noted in rickets, sprue, obstructive jaundice, nephrosis and glomerulonephritis.
Magnesium [show] .
This is mainly an intracellular divalent ion contained in the body in an amount of 15 mmol per 1 kg of body weight; the concentration of magnesium in plasma is 0.8-1.5 mmol/l, in erythrocytes 2.4-2.8 mmol/l. There is 10 times more magnesium in muscle tissue than in blood plasma. The level of magnesium in plasma, even with significant losses, can remain stable for a long time, replenished from the muscle depot.
Phosphorus [show] .
In the clinic, when testing blood, the following fractions of phosphorus are distinguished: total phosphate, acid-soluble phosphate, lipoid phosphate and inorganic phosphate. For clinical purposes, the determination of inorganic phosphate in blood plasma (serum) is often used.
Hypophosphatemia (decreased plasma phosphorus levels) is especially characteristic of rickets. It is very important that a decrease in the level of inorganic phosphate in the blood plasma is observed in the early stages of the development of rickets, when clinical symptoms are not sufficiently pronounced. Hypophosphatemia is also observed with insulin administration, hyperparathyroidism, osteomalacia, sprue and some other diseases.
Iron [show] .
In whole blood, iron is contained mainly in erythrocytes (- 18.5 mmol/l), in plasma its concentration averages 0.02 mmol/l. Every day, during the breakdown of hemoglobin in erythrocytes in the spleen and liver, about 25 mg of iron is released and the same amount is consumed during the synthesis of hemoglobin in the cells of hematopoietic tissues. The bone marrow (the main erythropoietic tissue of humans) contains a labile supply of iron that exceeds 5 times the daily requirement for iron. The supply of iron in the liver and spleen is significantly greater (about 1000 mg, i.e. a 40-day supply). An increase in iron content in blood plasma is observed with weakened hemoglobin synthesis or increased breakdown of red blood cells.
For anemia of various origins the need for iron and its absorption in the intestines increases sharply. It is known that in the intestine, iron is absorbed in the duodenum in the form of ferrous iron (Fe 2+). In the cells of the intestinal mucosa, iron combines with the protein apoferritin to form ferritin. It is assumed that the amount of iron entering the blood from the intestines depends on the content of apoferritin in the intestinal walls. Further transport of iron from the intestine to the hematopoietic organs occurs in the form of a complex with the blood plasma protein transferrin. Iron in this complex is in trivalent form. In the bone marrow, liver and spleen, iron is deposited in the form of ferritin - a kind of reserve of easily mobilized iron. In addition, excess iron can be deposited in tissues in the form of metabolically inert hemosiderin, well known to morphologists.
Lack of iron in the body can cause disruption of the last stage of heme synthesis - the conversion of protoporphyrin IX into heme. As a result of this, anemia develops, accompanied by an increase in the content of porphyrins, in particular protoporphyrin IX, in erythrocytes.
Minerals found in tissues, including blood, are very poorly large quantities ah (10 -6 -10 -12%) are called microelements. These include iodine, copper, zinc, cobalt, selenium, etc. It is believed that most trace elements in the blood are in a protein-bound state. Thus, plasma copper is part of ceruloplasmin, erythrocyte zinc belongs entirely to carbonic anhydrase, 65-76% of blood iodine is in organically bound form - in the form of thyroxine. Thyroxine is found in the blood mainly in protein-bound form. It complexes predominantly with the globulin that specifically binds it, which is located during electrophoresis of serum proteins between two fractions of α-globulin. Therefore, thyroxine-binding protein is called interalphaglobulin. Cobalt found in the blood is also found in protein-bound form and only partially as a structural component of vitamin B12. A significant portion of selenium in the blood is contained in active center enzyme glutathione peroxidase, and is also associated with other proteins.

Acid-base state

The acid-base state is the ratio of the concentrations of hydrogen and hydroxyl ions in biological media.

Considering the difficulty of using in practical calculations values of the order of 0.0000001, which approximately reflect the concentration of hydrogen ions, Zörenson (1909) proposed the use of negative decimal logarithms of the concentration of hydrogen ions. This indicator is named pH after the first letters of the Latin words puissance (potenz, power) hygrogen - “hydrogen power”. The ratios of the concentrations of acidic and basic ions corresponding to different pH values are given in table. 47.

It has been established that only a certain range of fluctuations in blood pH corresponds to the normal state - from 7.37 to 7.44 with an average value of 7.40. (In other biological fluids and in cells, the pH may differ from the pH of blood. For example, in red blood cells the pH is 7.19 ± 0.02, differing from the pH of blood by 0.2.)

No matter how small the limits of physiological pH fluctuations seem to us, nevertheless, if they are expressed in millimoles per 1 liter (mmol/l), it turns out that these fluctuations are relatively significant - from 36 to 44 ppm millimoles per 1 liter, i.e. e. constitute approximately 12% of the average concentration. More significant changes in blood pH towards increasing or decreasing the concentration of hydrogen ions are associated with pathological conditions.

Regulatory systems that directly ensure the constancy of blood pH are the buffer systems of the blood and tissues, the activity of the lungs and the excretory function of the kidneys.

Blood buffer systems

Buffer properties, i.e. the ability to counteract changes in pH when acids or bases are added to the system, are possessed by mixtures consisting of a weak acid and its salt with a strong base or a weak base with a salt of a strong acid.

The most important blood buffer systems are:

[show] .
Bicarbonate buffer system- a powerful and, perhaps, the most controllable system of extracellular fluid and blood. The bicarbonate buffer accounts for about 10% of the total buffer capacity of the blood. The bicarbonate system consists of carbon dioxide (H 2 CO 3) and bicarbonates (NaHCO 3 - in extracellular fluids and KHCO 3 - inside cells). The concentration of hydrogen ions in a solution can be expressed through the dissociation constant of carbonic acid and the logarithm of the concentration of undissociated H 2 CO 3 molecules and HCO 3 - ions. This formula is known as the Henderson-Hesselbach equation:
Since the true concentration of H 2 CO 3 is insignificant and is directly dependent on the concentration of dissolved CO 2, it is more convenient to use a version of the Henderson-Hesselbach equation containing the “apparent” dissociation constant of H 2 CO 3 (K 1), which takes into account the total concentration of CO 2 in solution. (The molar concentration of H 2 CO 3 compared to the concentration of CO 2 in the blood plasma is very low. At PCO 2 = 53.3 hPa (40 mm Hg), there are approximately 500 molecules of CO 2 per 1 molecule of H 2 CO 3.)
Then, instead of the concentration of H 2 CO 3, the concentration of CO 2 can be substituted:
In other words, at pH 7.4, the ratio between carbon dioxide physically dissolved in the blood plasma and the amount of carbon dioxide bound in the form of sodium bicarbonate is 1:20.
The mechanism of the buffering action of this system is that when large quantities of acidic products are released into the blood, hydrogen ions combine with bicarbonate anions, which leads to the formation of weakly dissociating carbonic acid.
In addition, excess carbon dioxide immediately decomposes into water and carbon dioxide, which is removed through the lungs as a result of their hyperventilation. Thus, despite a slight decrease in the concentration of bicarbonate in the blood, the normal ratio between the concentration of H 2 CO 3 and bicarbonate (1:20) is maintained. This ensures that the blood pH is kept within normal limits.
If the number of basic ions in the blood increases, they combine with weak carbonic acid to form bicarbonate anions and water. To maintain the normal ratio of the main components of the buffer system, in this case, physiological mechanisms for regulating the acid-base state are activated: a certain amount of CO 2 is retained in the blood plasma as a result of hypoventilation of the lungs, and the kidneys begin to secrete basic salts in larger quantities than usual (for example, Na 2 HP0 4). All this helps maintain a normal ratio between the concentration of free carbon dioxide and bicarbonate in the blood.
Phosphate buffer system [show] .
Phosphate buffer system constitutes only 1% of the buffer capacity of the blood. However, in tissues this system is one of the main ones. The role of acid in this system is played by monobasic phosphate (NaH 2 PO 4):
NaH 2 PO 4 -> Na + + H 2 PO 4 - (H 2 PO 4 - -> H + + HPO 4 2-),

and the role of the salt is dibasic phosphate (Na 2 HP0 4):
Na 2 HP0 4 -> 2Na + + HPO 4 2- (HPO 4 2- + H + -> H 2 PO 4 -).

For a phosphate buffer system, the following equation holds:
At pH 7.4, the ratio of the molar concentrations of monobasic and dibasic phosphates is 1:4.
The buffering effect of the phosphate system is based on the possibility of binding hydrogen ions with HPO 4 2- ions to form H 2 PO 4 - (H + + HPO 4 2- -> H 2 PO 4 -), as well as on the interaction of OH - ions with H 2 ions PO 4 - (OH - + H 4 PO 4 - -> HPO 4 2- + H 2 O).
The phosphate buffer in the blood is in close connection with the bicarbonate buffer system.
Protein buffer system [show] .
Protein buffer system- a fairly powerful buffer system of blood plasma. Since blood plasma proteins contain a sufficient amount of acidic and basic radicals, the buffering properties are associated mainly with the content of actively ionized amino acid residues—monoaminodicarboxylic and diaminomonocarboxylic acids—in the polypeptide chains. When the pH shifts to the alkaline side (remember the isoelectric point of the protein), the dissociation of basic groups is inhibited and the protein behaves like an acid (HPr). By binding with a base, this acid produces a salt (NaPr). For a given buffer system, the following equation can be written:
As pH increases, the amount of proteins in the form of salt increases, and as pH decreases, the amount of plasma proteins in the form of acid increases.
[show] .
Hemoglobin buffer system- the most powerful blood system. It is 9 times more powerful than bicarbonate: it accounts for 75% of the total buffer capacity of the blood. The participation of hemoglobin in the regulation of blood pH is associated with its role in the transport of oxygen and carbon dioxide. The dissociation constant of the acid groups of hemoglobin changes depending on its oxygen saturation. When hemoglobin is saturated with oxygen, it becomes a stronger acid (HHbO 2) and increases the release of hydrogen ions into the solution. If hemoglobin gives up oxygen, it becomes a very weak organic acid (HHb). The dependence of blood pH on the concentrations of HHb and KHb (or, respectively, HHbO 2 and KHb0 2) can be expressed by the following comparisons:
The hemoglobin and oxyhemoglobin systems are interconvertible systems and exist as a single whole; the buffer properties of hemoglobin are primarily due to the possibility of interaction of acid-reactive compounds with the potassium salt of hemoglobin to form an equivalent amount of the corresponding potassium salt of the acid and free hemoglobin:
KHb + H 2 CO 3 -> KHCO 3 + HHb.
It is in this way that the conversion of the potassium salt of hemoglobin of erythrocytes into free HHb with the formation of an equivalent amount of bicarbonate ensures that the pH of the blood remains within physiologically acceptable values, despite the entry into the venous blood of a huge amount of carbon dioxide and other acid-reactive metabolic products.
Once in the capillaries of the lungs, hemoglobin (HHb) is converted into oxyhemoglobin (HHbO 2), which leads to some acidification of the blood, displacement of some H 2 CO 3 from bicarbonates and a decrease in the alkaline reserve of the blood.
The alkaline reserve of the blood - the ability of the blood to bind CO 2 - is studied in the same way as total CO 2, but under conditions of balancing the blood plasma at PCO 2 = 53.3 hPa (40 mm Hg); determine the total amount of CO 2 and the amount of physically dissolved CO 2 in the test plasma. By subtracting the second from the first digit, we get a value called reserve blood alkalinity. It is expressed in volume percent CO 2 (volume of CO 2 in milliliters per 100 ml of plasma). Normally, a person's reserve alkalinity is 50-65 vol.% CO 2.

So, the listed blood buffer systems play an important role in the regulation of acid-base status. As noted, in this process, in addition to the blood buffer systems, the respiratory system and the urinary system also take an active part.

Acid-base disorders

In a condition where the body's compensatory mechanisms are unable to prevent changes in the concentration of hydrogen ions, a disorder of the acid-base state occurs. In this case, there are two opposite states- acidosis and alkalosis.

Acidosis is characterized by a concentration of hydrogen ions above normal limits. In this case, naturally, the pH decreases. A decrease in pH value below 6.8 causes death.

In cases where the concentration of hydrogen ions decreases (accordingly, the pH increases), a state of alkalosis occurs. The limit of compatibility with life is pH 8.0. In clinics, pH values such as 6.8 and 8.0 are practically not found.

Depending on the mechanism, the development of acid-base disorders, respiratory (gas) and non-respiratory (metabolic) acidosis or alkalosis are distinguished.

acidosis [show] .
Respiratory (gas) acidosis may occur as a result of a decrease in minute breathing volume (for example, with bronchitis, bronchial asthma, emphysema, mechanical asphyxia, etc.). All these diseases lead to hypoventilation of the lungs and hypercapnia, i.e., an increase in arterial blood PCO 2. Naturally, the development of acidosis is prevented by blood buffer systems, in particular the bicarbonate buffer. The bicarbonate content increases, i.e. the alkaline reserve of the blood increases. At the same time, the excretion in urine of free and bound ammonium salts of acids increases.
Non-respiratory (metabolic) acidosis caused by the accumulation of organic acids in tissues and blood. This type of acidosis is associated with metabolic disorders. Non-respiratory acidosis is possible with diabetes (accumulation of ketone bodies), fasting, fever and other diseases. Excess accumulation hydrogen ions in these cases are initially compensated by reducing the alkaline reserve of the blood. The CO 2 content in the alveolar air is also reduced, and pulmonary ventilation is accelerated. The acidity of urine and the concentration of ammonia in the urine are increased.

alkalosis [show] .

Respiratory (gas) alkalosis occurs with a sharp increase respiratory function lungs (hyperventilation). For example, when inhaling pure oxygen, compensatory shortness of breath that accompanies a number of diseases, when being in a rarefied atmosphere and other conditions, respiratory alkalosis can be observed.

Due to a decrease in the content of carbonic acid in the blood, a shift occurs in the bicarbonate buffer system: part of the bicarbonates is converted into carbonic acid, i.e., the reserve alkalinity of the blood decreases. It should also be noted that PCO 2 in the alveolar air is reduced, pulmonary ventilation is accelerated, urine has low acidity and the ammonia content in urine is reduced.

Non-respiratory (metabolic) alkalosis develops with the loss of a large number of acid equivalents (for example, uncontrollable vomiting, etc.) and the absorption of alkaline equivalents of intestinal juice that have not been neutralized by acidic gastric juice, as well as with the accumulation of alkaline equivalents in tissues (for example, with tetany) and in the case of unreasonable correction of metabolic acidosis. At the same time, the alkaline reserve of the blood and PCO 2 in the avelveolar air increase. Pulmonary ventilation is slowed down, the acidity of urine and the ammonia content in it are reduced (Table 48).

Table 48. The simplest indicators for assessing acid-base status
Shifts (changes) in acid-base state	Urine, pH	Plasma, HCO 2 -, mmol/l	Plasma, HCO 2 -, mmol/l
Norm	6-7	25	0,625
Respiratory acidosis	reduced	increased	increased
Respiratory alkalosis	increased	reduced	reduced
Metabolic acidosis	reduced	reduced	reduced
Metabolic alkalosis	increased	increased	increased

In practice, isolated forms of respiratory or non-respiratory disorders are extremely rare. Determining a set of indicators of acid-base status helps to clarify the nature of the disorders and the degree of compensation. Over the past decades, sensitive electrodes for direct measurement of pH and PCO 2 of blood have become widespread to study indicators of acid-base status. IN clinical settings It is convenient to use devices such as "Astrup" or domestic devices - AZIV, AKOR. Using these instruments and corresponding nomograms, the following basic indicators of acid-base status can be determined:

actual blood pH is the negative logarithm of the concentration of hydrogen ions in the blood under physiological conditions;
actual PCO 2 of whole blood - partial pressure of carbon dioxide (H 2 CO 3 + CO 2) in the blood under physiological conditions;
actual bicarbonate (AB) - the concentration of bicarbonate in blood plasma under physiological conditions;
standard blood plasma bicarbonate (SB) - the concentration of bicarbonate in blood plasma, balanced by alveolar air and at full saturation with oxygen;
buffer bases of whole blood or plasma (BB) - an indicator of the power of the entire buffer system of blood or plasma;
normal whole blood buffer bases (NBB) - whole blood buffer bases at physiological values pH and PCO 2 of alveolar air;
base excess (BE) is an indicator of excess or lack of buffer capacity (BB - NBB).

Blood functions

Blood ensures the vital functions of the body and performs the following important functions:

respiratory - supplies cells with oxygen from the respiratory organs and removes carbon dioxide (carbon dioxide) from them;
nutritious - carries nutrients throughout the body that, during digestion, enter the blood vessels from the intestines;
excretory - removes from organs decay products formed in cells as a result of their vital activity;
regulatory - transports hormones that regulate metabolism and work different organs, carries out humoral communication between organs;
protective - microorganisms that enter the blood are absorbed and neutralized by leukocytes, and the toxic waste products of microorganisms are neutralized with the participation of special blood proteins - antibodies.
All these functions are often combined under a common name - the transport function of blood.
In addition, blood maintains the constancy of the internal environment of the body - temperature, salt composition, environmental reaction, etc.

Nutrients from the intestines, oxygen from the lungs, and metabolic products from tissues enter the blood. However, blood plasma remains relatively constant in composition and physical and chemical properties. The constancy of the internal environment of the body - homeostasis is maintained by the continuous work of the digestive, respiratory, and excretory organs. The activities of these bodies are regulated nervous system, responding to changes in the external environment and ensuring the alignment of shifts or disturbances in the body. In the kidneys, the blood is freed from excess mineral salts, water and metabolic products, in the lungs - from carbon dioxide. If the concentration of any substance in the blood changes, then neurohormonal mechanisms, regulating the activity of a number of systems, reduce or increase its release from the body.

Some blood plasma proteins play an important role in blood coagulation and anticoagulation systems.

Blood clotting- a protective reaction of the body that protects it from blood loss. People whose blood is unable to clot suffer from a serious disease - hemophilia.

The mechanism of blood clotting is very complex. Its essence is the formation of a blood clot - a thrombus that clogs the wound area and stops bleeding. A blood clot is formed from the soluble protein fibrinogen, which during the blood clotting process turns into the insoluble protein fibrin. The conversion of soluble fibrinogen into insoluble fibrin occurs under the influence of thrombin, an active enzyme protein, as well as a number of substances, including those released during the destruction of platelets.

The blood clotting mechanism is triggered by a cut, puncture, or injury, leading to damage to the platelet membrane. The process takes place in several stages.

When platelets are destroyed, the enzyme protein thromboplastin is formed, which, when combined with calcium ions present in the blood plasma, converts the inactive plasma protein enzyme prothrombin into active thrombin.

In addition to calcium, other factors also take part in the blood clotting process, such as vitamin K, without which the formation of prothrombin is disrupted.

Thrombin is also an enzyme. It completes the formation of fibrin. The soluble protein fibrinogen turns into insoluble fibrin and precipitates in the form of long threads. From the network of these threads and blood cells that linger in the network, an insoluble clot is formed - a thrombus.

These processes occur only in the presence of calcium salts. Therefore, if calcium is removed from the blood by binding it chemically (for example, with sodium citrate), then such blood loses its ability to clot. This method is used to prevent blood clotting during preservation and transfusion.

Internal environment of the body

Blood capillaries do not approach every cell, so the exchange of substances between cells and blood, communication between the organs of digestion, respiration, excretion, etc. carried out through the internal environment of the body, which consists of blood, tissue fluid and lymph.

Internal environment	Compound	Location	Source and place of formation	Functions
Blood	Plasma (50-60% of blood volume): water 90-92%, proteins 7%, fats 0.8%, glucose 0.12%, urea 0.05%, mineral salts 0.9%	Blood vessels: arteries, veins, capillaries	Due to the absorption of proteins, fats and carbohydrates, as well as mineral salts of food and water	The relationship of all organs of the body as a whole with the external environment; nutritional (delivery of nutrients), excretory (removal of dissimilation products, CO 2 from the body); protective (immunity, coagulation); regulatory (humoral)
Blood	Formed elements (40-50% of blood volume): red blood cells, leukocytes, platelets	Blood plasma	Red bone marrow, spleen, lymph nodes, lymphoid tissue	Transport (respiratory) - red blood cells transport O 2 and partially CO 2; protective - leukocytes (phagocytes) neutralize pathogens; platelets provide blood clotting
Tissue fluid	Water, nutrient organic and inorganic substances dissolved in it, O 2, CO 2, dissimilation products released from cells	The spaces between the cells of all tissues. Volume 20 l (for an adult)	Due to blood plasma and end products of dissimilation	It is an intermediate medium between blood and body cells. Transfers O2, nutrients, mineral salts, and hormones from the blood to the cells of organs. Returns water and dissimilation products to the bloodstream through lymph. Transfers CO2 released from cells into the bloodstream
Lymph	Water, decay products of organic substances dissolved in it	Lymphatic system, consisting of lymphatic capillaries ending in sacs and vessels merging into two ducts that empty into the vena cava of the circulatory system in the neck	Due to tissue fluid absorbed through sacs at the ends of lymphatic capillaries	Return of tissue fluid to the bloodstream. Filtration and disinfection of tissue fluid, which is carried out in the lymph nodes where lymphocytes are produced

The liquid part of the blood - plasma - passes through the walls of the thinnest blood vessels - capillaries - and forms intercellular, or tissue, fluid. This fluid washes all the cells of the body, gives them nutrients and takes away metabolic products. In the human body there is up to 20 liters of tissue fluid; it forms the internal environment of the body. Most of this fluid returns to the blood capillaries, and a smaller part, penetrating into those closed at one end lymphatic capillaries, forms lymph.

The color of the lymph is yellowish-straw. It is 95% water and contains proteins, mineral salts, fats, glucose, and lymphocytes (a type of white blood cell). The composition of lymph resembles that of plasma, but there are fewer proteins, and it has its own characteristics in different parts of the body. For example, in the intestinal area there are a lot of fat droplets, which gives it a whitish color. Lymph travels through the lymphatic vessels to the thoracic duct and through it enters the blood.

Nutrients and oxygen from the capillaries, according to the laws of diffusion, first enter the tissue fluid, and from it are absorbed by the cells. This is how the connection between capillaries and cells occurs. Carbon dioxide, water and other metabolic products formed in cells are also released from the cells first into the tissue fluid due to the difference in concentrations, and then enter the capillaries. Arterial blood becomes venous and delivers waste products to the kidneys, lungs, and skin, through which they are removed from the body.

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 immune reaction In immunity, in addition to phagocyte cells, chemical compounds - antibodies (special proteins that neutralize antigens - foreign cells, proteins and poisons) also take part. 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 about healing powers organism, in which the phagocytic theory of immunity was first expounded) 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 disease in mild form 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, thanks 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.

The immune system, through phagocytosis and the production of antibodies, protects the body from infectious diseases, frees it from dead, degenerated and foreign cells, 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 different types animals 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 most important defensive reaction body. 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 threads fibrin 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.