The composition, quantity and function of blood is briefly. Functions of the blood. The main buffer systems of the body

Blood- this 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 (platelets) (Fig.). 1 mm 3 of blood contains 4.5-5 million erythrocytes, 5-8 thousand leukocytes, 200-400 thousand platelets.

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

Most of all, sodium and chloride ions are in the plasma, therefore, with large blood loss, an isotonic solution containing 0.85% sodium chloride is injected into the veins to maintain the work of the heart.

The red color of blood is given by red blood cells containing a red respiratory pigment - hemoglobin, which attaches oxygen in the lungs and gives it to the tissues. Oxygen-rich blood is called arterial, and oxygen-depleted blood is called venous.

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

If you let the blood clot and then separate the clot, you get blood serum. Serum is the same plasma, devoid of fibrinogen, which was part of the blood clot.

Physically and chemically, 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 keeping blood pressure at a constant level.

Blood, carrying out the transport of chemicals in the body, combines biochemical processes occurring in different cells and intercellular spaces into a single system. Such a close relationship of blood with all tissues of the body allows you to maintain a relatively constant chemical composition of blood due to powerful regulatory mechanisms (CNS, hormonal systems, etc.) that provide a clear relationship in the work of such vital organs and tissues as the liver, kidneys, lungs and heart. -vascular system. All random fluctuations in the composition of the blood in a healthy body are quickly aligned.

In many pathological processes, more or less abrupt changes in the chemical composition of the blood are noted, which signal violations in the state of human health, allow you 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 of blood	Functions
red blood cells	Red non-nucleated blood cells of a biconcave shape containing a protein - hemoglobin	red bone marrow	3-4 months	Spleen. Hemoglobin is broken down in the liver	4.5-5 million	Transport of O 2 from lungs to tissues and CO 2 from tissues to lungs
Leukocytes	Amoeba white blood cells with a nucleus	Red bone marrow, spleen, lymph nodes	3-5 days	Liver, spleen, as well as places where the inflammatory process takes place	6-8 thousand	Protection of the body from pathogenic microbes by phagocytosis. Produce antibodies to build immunity
platelets	Blood non-nuclear bodies	red bone marrow	5-7 days	Spleen	300-400 thousand	Participate in blood clotting when a blood vessel is damaged, contributing to the conversion of fibrinogen protein into fibrin - a fibrous blood clot

Erythrocytes or red blood cells, are small (7-8 microns in diameter) non-nucleated cells that have the shape of a biconcave disk. The absence of a nucleus allows the erythrocyte to contain a large amount of hemoglobin, and the shape contributes to an increase in its surface. In 1 mm 3 of blood, there are 4-5 million red blood cells. The number of red blood cells in the blood is not constant. It increases with rise in height, large losses of water, etc.

Erythrocytes throughout a person's life are formed from nuclear cells in the red bone marrow of the cancellous bone. In the process of maturation, they lose the nucleus and enter the bloodstream. The lifespan of human erythrocytes 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 carry oxygen and partly 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 a globin protein. 100 ml of human blood contains an average of 14 g of hemoglobin. In the pulmonary capillaries, hemoglobin, combining with oxygen, forms an unstable compound - oxidized hemoglobin (oxyhemoglobin) due to the heme ferrous iron. In the capillaries of tissues, hemoglobin gives up its oxygen and turns into reduced hemoglobin of a darker color, therefore, venous blood flowing from the tissues has a dark red color, and arterial blood rich in oxygen is scarlet.

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

Carbon dioxide formed in the tissues enters the red blood cells and, interacting with hemoglobin, turns into salts of carbonic acid - bicarbonates. This transformation takes place in several stages. Oxyhemoglobin in arterial 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 + HCO - 3;
KHb + H + HCO - 3 → H Hb + K + HCO - 3;

The potassium bicarbonate formed as a result of the reaction dissociates and its anion, due to the 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 chloride ions, which diffuse from the plasma into the erythrocytes. In this case, the dissociated sodium bicarbonate salt is formed in the plasma, and the same dissociated salt of potassium chloride 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 proceeds only to equalize its concentration in the erythrocyte and plasma.

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 split by the same enzyme to H 2 O and CO 2, but as the content of HCO 3 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, blood oxygen is bound to hemoglobin, and carbon dioxide is in the form of bicarbonate salts.

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

Leukocytes or white blood cells, - colorless blood cells with a diameter of 8-30 microns, inconstant shape, having a nucleus; The normal number of leukocytes in the blood is 6-8 thousand in 1 mm 3. Leukocytes are formed in the red bone marrow, liver, spleen, lymph nodes; their life expectancy can vary from several hours (neutrophils) to 100-200 or more days (lymphocytes). They are also destroyed in the spleen.

By structure, leukocytes are divided into several [the link is available to registered users who have 15 posts on the forum], each of which performs certain 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, foreign bodies. [show] .

According to modern views, the protection of the body, i.e. its immunity to various factors that carry genetically alien information is provided by immunity, represented by a variety of cells: leukocytes, lymphocytes, macrophages, etc., due to which foreign cells or complex organic substances that have entered the body that differ from the cells and substances of the body are destroyed and eliminated .

Immunity maintains the genetic constancy of the organism in ontogeny. When cells divide due to mutations in the body, cells with a modified genome are often formed. In order for these mutant cells not to lead to disturbances in the development of organs and tissues in the course of further division, 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), the ability of leukocytes 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, is of great importance for immunity. In plasma, antibodies stick together foreign proteins 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 the human body has specific antibodies, it becomes immune to certain infectious diseases.

Distinguish between 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 the transfer of any infectious disease, when antibodies form in the blood plasma in response to the ingress of foreign proteins of this microorganism. In this case, there is a natural, acquired immunity.

Immunity can be developed artificially if weakened or killed pathogens of any disease are introduced into the human body (for example, smallpox vaccination). This immunity does not appear immediately. For its manifestation, it takes time for the body to develop antibodies against the introduced weakened microorganism. Such immunity usually lasts for years and is called active.

The first vaccination in the world - 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 immunity (for example, anti-measles serum). It manifests itself immediately after the introduction of serum, persists for 4-6 weeks, and then the antibodies are gradually destroyed, immunity weakens, and to maintain it, repeated administration of immune serum is necessary.

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 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 draw them into the cell, where they are split with the participation of enzymes (intracellular digestion). In the process of interaction with foreign bodies, many leukocytes die. At the same time, decay products accumulate around the foreign body and pus forms.

This phenomenon was discovered by I. I. Mechnikov. Leukocytes, capturing various microorganisms and digesting them, I. I. Mechnikov called phagocytes, and the very phenomenon of absorption and digestion - 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). He discovered the phenomenon of phagocytosis. Developed problems of immunity. Together with N. F. Gamaleya, he founded in Odessa the first bacteriological station in Russia (at present, the II Mechnikov Research Institute). He was awarded prizes: two to them. 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 leukocytes can be harmful, for example, in organ transplants. Leukocytes react to transplanted organs in the same way as to pathogenic microorganisms - they phagocytize and destroy them. To avoid an undesirable reaction of leukocytes, phagocytosis is inhibited by special substances.

Platelets, or 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, 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.

Plasma proteins

Of the 9-10% 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 the blood plasma is 40-50 g/l, globulins - 20-30 g/l, fibrinogen - 2-4 g/l. Blood plasma devoid of fibrinogen is called serum.

The synthesis of blood plasma proteins is carried out mainly in the cells of the liver and reticuloendothelial system. The physiological role of blood plasma proteins is multifaceted.

1. Proteins maintain colloid osmotic (oncotic) pressure and thus a constant blood volume. The content of proteins in plasma is much higher than in tissue fluid. Proteins, being colloids, bind water and retain it, preventing it from leaving the bloodstream. Despite the fact that the oncotic pressure is only a small part (about 0.5%) of the total osmotic pressure, it is it that determines the predominance of the osmotic pressure of the blood over the osmotic pressure of the tissue fluid. It is known that in the arterial part of the capillaries, as a result of hydrostatic pressure, protein-free blood fluid penetrates into the tissue space. This happens up to a certain moment - the "turning point", when the falling hydrostatic pressure becomes equal to the colloid osmotic pressure. After the "turning" moment in the venous part of the capillaries, a reverse flow of fluid from the tissue occurs, since now the hydrostatic pressure is less than the colloid osmotic pressure. Under other conditions, as a result of hydrostatic pressure in the circulatory system, water would seep into the tissues, which would cause swelling of various organs and subcutaneous tissue.
2. Plasma proteins are actively involved in blood clotting. A number of plasma proteins, including fibrinogen, are major components of the blood coagulation system.
3. Plasma proteins to a certain extent determine the viscosity of the blood, which, as already noted, is 4-5 times higher than the viscosity of water and plays an important role in maintaining hemodynamic relationships in the circulatory system.
4. Plasma proteins are involved in maintaining a constant blood pH, as they constitute one of the most important buffer systems in the blood.
5. The transport function of blood plasma proteins is also important: combining with a number of substances (cholesterol, bilirubin, etc.), as well as with drugs (penicillin, salicylates, etc.), they transfer them to the tissue.
6. Plasma proteins play an important role in immune processes (especially immunoglobulins).
7. As a result of the formation of non-dialyzable compounds with gglasma proteins, the level of cations in the blood is maintained. For example, 40-50% of serum calcium is associated with proteins, a significant part of iron, magnesium, copper and other elements are also associated with serum proteins.
8. Finally, blood plasma proteins can serve as a reserve of amino acids.

Modern physical and chemical 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: albumins, α 1, α 2, β- and γ-globulins (Fig. 125). By electrophoresis in agar gel in blood serum, up to 7-8 fractions are detected, 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 of electrophoresis has not yet been finally established. When the electrophoresis conditions change, as well as during electrophoresis in various media (for example, in starch or polyacrylamide gel), the migration rate and, consequently, the order of the protein bands can change.

An even greater number of protein fractions (about 30) can be obtained using the immunoelectrophoresis method. Immunoelectrophoresis is a kind of combination of electrophoretic and immunological methods for 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. On fig. 126 shows a typical immunoelectropherogram of human serum proteins.

Characteristics of the main protein fractions

• Albumins [show] .

  Albumin accounts for more than half (55-60%) of human plasma proteins. The molecular weight of albumins is about 70,000. Serum albumins are relatively quickly renewed (the half-life of human albumins is 7 days).

  Due to their high hydrophilicity, especially due to their relatively small molecular size and significant serum concentration, albumins play an important role in maintaining the colloid osmotic pressure of the blood. It is known that serum albumin concentration below 30 g/l causes significant changes in blood oncotic pressure, which leads to edema. Albumins perform an important function of transporting many biologically active substances (in particular, hormones). They are able to bind to cholesterol, bile pigments. A significant portion of serum calcium is also associated with albumin.

  During starch gel electrophoresis, 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 ordinary 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 ordinary albumin. There are other rare variants of albumin (Reeding albumin, Gent albumin, Maki albumin). Inheritance of albumin polymorphism occurs in an autosomal codominant manner and is observed in several generations.

  In addition to the hereditary polymorphism of albumins, transient bisalbuminemia occurs, which in some cases can be mistaken for congenital. The appearance of a fast component of albumin in patients treated with large doses of penicillin is described. After the abolition 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] .

  Serum globulins, when salted out with neutral salts, 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, which are capable of separating into a number of subfractions during electrophoresis, especially in starch or polyacrylamide gels. It is known that α- and β-globulin fractions contain lipoproteins and glycoproteins. Among the components of α- and β-globulins, there are also proteins associated with metals. Most of the antibodies contained in the 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 a change in both the total amount of blood plasma proteins and the percentage of individual protein fractions.

As noted, α- and β-globulin fractions of blood serum proteins contain lipoproteins and glycoproteins. The composition of 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 blood serum glycoproteins is different.

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

Neuraminic 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 α 1 - and α 2 -fractions of globulins. Glycoproteins associated with α-globulin fractions contain little fucose; at the same time, glycoproteins found in the composition of β- and especially γ-globulin fractions contain fucose in a significant amount.

An increased content of glycoproteins in plasma or blood 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 in rheumatism of the basic substance of the connective tissue, which leads to the entry of glycoproteins into the blood.

Plasma lipoproteins- these are complex complex compounds that have a characteristic structure: inside the lipoprotein particle there is a fat drop (core) containing non-polar lipids (triglycerides, esterified cholesterol). The fat drop is surrounded by a shell, which includes 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 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, 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). Correspond on electrophoretic mobility to β-globulins. They are the richest class of lipoproteins in cholesterol. 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 (XM). They do not move during electrophoresis either to the cathode or to the anode and remain at the start (the place of application of the test sample of plasma or serum). Formed in the intestinal wall during the absorption of exogenous triglycerides and cholesterol. First, XM enters the thoracic lymphatic duct, and from it into the bloodstream. XM are the main transport form of exogenous triglycerides. The blood plasma of healthy people who have not taken food for 12-14 hours does not contain HM.

It is believed that the main place for the formation of plasma pre-β-lipoproteins and α-lipoproteins is the liver, and β-lipoproteins are formed already from pre-β-lipoproteins in the blood plasma when they are acted upon by lipoprotein lipase.

It should be noted that lipoprotein electrophoresis can be carried out both on paper and in agar, starch and polyacrylamide gel, cellulose acetate. When choosing an electrophoresis method, the main criterion is a clear receipt of four types of lipoproteins. The most promising at present is electrophoresis of lipoproteins in polyacrylamide gel. In this case, the fraction of pre-β-lipoproteins is detected between HM and β-lipoproteins.

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

According to the existing classification of hyperlipoproteinemias, the following five types of deviations 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 HM, normal or slightly increased content of pre-β-lipoproteins. A sharp increase in the level of triglycerides in the blood serum. Clinically, this condition is manifested by xanthomatosis.
• Type II - hyper-β-lipoproteinemia. This type is divided into two subtypes:
  • IIa, characterized by a high content 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, high, and in some cases very high, cholesterol levels in the blood plasma are noted. 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, often developing coronary heart disease.

• Type III - "floating" hyperlipoproteinemia or dys-β-lipoproteinemia. In the blood serum, lipoproteins appear with an unusually high cholesterol content and high electrophoretic mobility ("pathological" or "floating" β-lipoproteins). They accumulate in the blood due to impaired conversion of pre-β-lipoproteins to β-lipoproteins. This type of hyperlipoproteinemia is often combined with various manifestations of atherosclerosis, including coronary heart disease and damage to the vessels of the legs.
• Type IV - hyperpre-β-lipoproteinemia. An increase in the level of pre-β-lipoproteins, the normal content of β-lipoproteins, the absence of HM. An increase in triglyceride levels with normal or slightly elevated cholesterol levels. Clinically, this type is combined with diabetes, obesity, coronary heart disease.
• Type V - hyperpre-β-lipoproteinemia and chylomicronemia. There is an increase in the level of pre-β-lipoproteins, the presence of HM. Clinically manifested by xanthomatosis, sometimes combined with latent diabetes. Ischemic heart disease is not observed in this type of hyperlipoproteinemia.

Some of the most studied and clinically interesting plasma proteins

• Haptoglobin [show] .

  Haptoglobin is part of the α 2 -globulin fraction. This protein has the ability to bind to hemoglobin. The resulting haptoglobin-hemoglobin complex can be absorbed by the reticuloendothelial system, thereby preventing the loss of iron, which is part of hemoglobin, both during its physiological and pathological release from erythrocytes.

  Electrophoresis revealed three groups of haptoglobins, which were designated as Hp 1-1, Hp 2-1 and Hp 2-2. It has been established that there is a connection between the inheritance of haptoglobin types and Rh antibodies.

• Trypsin inhibitors [show] .

  It is known that during electrophoresis of blood plasma proteins, proteins capable of inhibiting trypsin and other proteolytic enzymes move in the zone of α 1 and α 2 -globulins. Normally, the content of these proteins is 2.0-2.5 g / l, but during inflammatory processes in the body, during pregnancy and a number of other conditions, the content of proteins - inhibitors of proteolytic enzymes increases.

• Transferrin [show] .

  Transferrin refers to β-globulins and has the ability to combine with iron. Its complex with iron is colored orange. In the iron transferrin complex, iron is in the trivalent form. The serum transferrin concentration is about 2.9 g/l. Normally, only 1/3 of transferrin is saturated with iron. Therefore, there is a certain reserve of transferrin capable of binding iron. Transferrin can be of different types in different people. 19 types of transferrin have been identified, differing in the charge of the protein molecule, its amino acid composition, and the number of sialic acid molecules associated with the protein. The detection of different types of transferrins is associated with heredity.

• ceruloplasmin [show] .

  This protein has a bluish color due to the presence of 0.32% copper in its composition. Ceruloplasmin is an oxidase of ascorbic acid, adrenaline, dihydroxyphenylalanine and some other compounds. With hepatolenticular degeneration (Wilson-Konovalov's disease), the content of ceruloplasmin in the blood serum is significantly reduced, which is an important diagnostic test.

  Enzyme electrophoresis revealed the presence of four ceruloplasmin isoenzymes. Normally, two isoenzymes are found in the blood serum of adults, which differ markedly in their mobility during electrophoresis in acetate buffer at pH 5.5. In the serum of newborns, two fractions were also found, but these fractions have a higher electrophoretic mobility than adult ceruloplasmin isoenzymes. It should be noted that in terms of its electrophoretic mobility, the isoenzyme spectrum of ceruloplasmin in the blood serum in patients with Wilson-Konovalov disease is similar to the isoenzyme spectrum of newborns.

• C-reactive protein [show] .

  This protein got its name as a result of the ability to enter into a precipitation reaction with pneumococcal C-polysaccharide. C-reactive protein is absent in the blood serum of a healthy organism, but is found in many pathological conditions accompanied by inflammation and tissue necrosis.

  C-reactive protein appears during the acute period of the disease, so it is sometimes called the "acute phase" protein. With the transition to the chronic phase of the disease, C-reactive protein disappears from the blood and reappears during an exacerbation of the process. During electrophoresis, the protein moves together with α 2 -globulins.

• cryoglobulin [show] .

  cryoglobulin in the blood serum of healthy people is also absent and appears in it under pathological conditions. A distinctive property of this protein is the ability to precipitate or gelate when the temperature drops below 37°C. During electrophoresis, cryoglobulin most often moves together with γ-globulins. Cryoglobulin can be found in the blood serum in myeloma, nephrosis, liver cirrhosis, rheumatism, lymphosarcoma, leukemia and other diseases.

• Interferon [show] .

  Interferon- a specific protein synthesized in the cells of the body as a result of exposure to viruses. In turn, this protein has the ability to inhibit the reproduction of the virus in cells, but does not destroy existing viral particles. The interferon formed in the cells easily enters the bloodstream and from there again penetrates the tissues and cells. Interferon has species specificity, although not absolute. For example, monkey interferon inhibits viral replication in cultured human cells. The protective effect of interferon largely depends on the ratio between the rates of spread of the virus and interferon in the blood and tissues.

• Immunoglobulins [show] .

  Until recently, there were four main classes of immunoglobulins that make up the y-globulin fraction: IgG, IgM, IgA, and IgD. In recent years, a fifth class of immunoglobulins, IgE, has been discovered. Immunoglobulins practically have a single structural plan; they consist of two heavy polypeptide chains H (mol. m. 50,000-75,000) and two light chains L (mol. w. ~ 23,000) connected by three disulfide bridges. In this case, human immunoglobulins can contain two types of chains L (K or λ). In addition, each class of immunoglobulins has its own type of H heavy chains: 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, such as myeloma proteins, the enhanced synthesis of which occurs in multiple myeloma. As already noted, in the blood in this disease, myeloma proteins accumulate in relatively high concentrations, and Bence-Jones protein is found in the urine. It turned out that the Bens-Jones protein consists of L-chains, which, apparently, are synthesized in the patient's body in excess in comparison with H-chains and therefore are excreted in the urine. The C-terminal half of the polypeptide chain of Bence-Jones protein molecules (actually L-chains) in all patients with myeloma has the same sequence, and the N-terminal half (107 amino acid residues) of L-chains has a different primary structure. The study of the H-chains of myeloma plasma proteins also revealed an important pattern: the N-terminal fragments of these chains in different patients have an unequal primary structure, 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 the blood serum changes significantly. So, in chronic aggressive hepatitis, there is an increase in IgG, in alcoholic cirrhosis - IgA, and in 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 are deficient in IgA are more likely to develop infectious diseases. It can be assumed that this is a consequence of the insufficiency of the synthesis of a certain part of the antibodies.

  Complement system

  The human serum complement system includes 11 proteins with a molecular weight of 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 by their lysis is observed, as well as the activation of leukocytes and their absorption of foreign cells as a result of phagocytosis.

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

  1. "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);
  2. both peptides on another site on the surface of the target cell interact with three proteins of the "activating group" of the complement system, while the formation of two peptides also occurs;
  3. 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 site of the target cell surface. The binding of proteins of the "membrane attack" group to the cell surface destroys it by forming through channels in the membrane.

  Plasma (serum) enzymes

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

  • Secretory - being 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 coagulation (see p. 639). Serum cholinesterase also 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. With the defeat of certain tissues, 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.). These enzymes under physiological conditions are mainly excreted in the bile. The mechanisms regulating the flow of these enzymes into the bile capillaries have not yet been fully elucidated. In many pathological processes, the excretion of these enzymes with bile is disturbed and the activity of excretory enzymes in the blood plasma increases.

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

  Thus, from the point of view of the diagnostic value of the study of the activity of enzymes in the blood serum in acute myocardial infarction, it can be compared with the electrocardiographic diagnostic method introduced several decades ago. Determination of enzyme activity in myocardial infarction is advisable in cases where the course of the disease and electrocardiography 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 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 changes significantly in the blood serum, and the activity of histidase, urocaninase also 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; ornithinecarbamoyltransferase and, to a 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, a particularly important laboratory test has been the study of the activity of isoenzymes in the blood serum, in particular lactate dehydrogenase isoenzymes.

  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 LDH 1 isoenzymes and partly LDH 2 isoenzymes sharply increase in the blood serum. The isoenzyme spectrum of lactate dehydrogenase in the blood serum in myocardial infarction resembles the isoenzyme spectrum of the heart muscle. On the contrary, with parenchymal hepatitis in the blood serum, the activity of isoenzymes LDH 5 and LDH 4 significantly increases and the activity of LDH 1 and LDH 2 decreases.

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

  Creatine kinase isoenzymes are especially important to study in acute myocardial infarction, since the MB-form is found in significant amounts almost exclusively 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 the activity of enzymes in the blood serum in many pathological processes is due to at least two reasons: 1) the release of enzymes from damaged areas of organs or tissues into the bloodstream 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 in the event of a breakdown in the mechanisms of intracellular regulation of metabolism is associated with the termination 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 determines 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 blood nitrogen includes urea nitrogen (50% of the total amount of non-protein nitrogen), amino acids (25%), ergothioneine - a compound that is part of 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 blood nitrogen includes mainly nitrogen of the end products of the metabolism of simple and complex proteins.

  Non-protein blood nitrogen is also called residual nitrogen, i.e., remaining in the filtrate after protein precipitation. In a healthy person, fluctuations in the content of non-protein, or residual, nitrogen in the blood are insignificant and mainly depend on the amount of proteins ingested with 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 causes 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 with their normal entry into the bloodstream. It, in turn, can be renal and 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 in retention renal azotemia occurs mainly due to urea. In these cases, urea nitrogen accounts for 90% of non-protein blood nitrogen instead of the normal 50%. 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 it has been formed in the kidney.

  Table 46. The content of free amino acids in human blood plasma
  Amino acids	Content, µmol/l
  Alanine	360-630
  Arginine	92-172
  Asparagine	50-150
  Aspartic acid	150-400
  Valine	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
  Serene	110
  Threonine	160-176
  tryptophan	49
  Tyrosine	78-83
  Phenylalanine	85-115
  citrulline	10-50
  cystine	84-125

  Production azotemia observed with excessive intake of nitrogen-containing products into the blood, as a result of increased breakdown of tissue proteins. Mixed azotemias are 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 (the norm is 3.3-6.6 mmol / l). An increase in the content of urea in the blood to 16.6-20.0 mmol / l (calculated as urea nitrogen [The value of the urea nitrogen content is approximately 2 times, or rather 2.14 times less than the number expressing the concentration of urea.]) is a sign renal dysfunction of moderate severity, up to 33.3 mmol / l - severe and over 50 mmol / l - a very severe violation with a poor prognosis. Sometimes a special coefficient or, more precisely, the ratio of blood urea nitrogen to residual blood nitrogen is determined, 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 with a violation of the urea-forming function of the liver, the coefficient decreases (below 45%).

  Uric acid is also an important protein-free nitrogenous substance in the blood. 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 the blood 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 rises to 0.47-0.89 mmol / l and even up to 1.1 mmol / l; The composition of the residual nitrogen also includes the nitrogen of amino acids and polypeptides.

  The blood constantly contains a certain amount of free amino acids. Some of them are of exogenous origin, that is, they enter the blood from the 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, there are aspartic acid, asparagine, cysteine, and many other amino acids that are part of natural proteins in the blood. 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 concentration of amino acid nitrogen in erythrocytes to the content of amino acid nitrogen in plasma ranges from 1.52 to 1.82. This ratio (coefficient) is very constant, and only in some diseases is its deviation from the norm observed.

  The total determination of the level of polypeptides in the blood is relatively rare. 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 the kinin system of the blood

  Kinins are sometimes referred to as 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 blood plasma. Kinins are characterized by a wide spectrum of biological action. This action is mainly directed to the smooth muscles of the vessels and the capillary membrane; hypotensive action 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 that regulates local and general blood flow and the permeability of the vascular wall.

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

  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 blood plasma with the α 2 -globulin fraction. The site of synthesis of kininogens 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 HOOC groups of arginine or lysine are involved; protein proteolysis in a broad sense is not characteristic of these enzymes.

  There are plasma kallikreins and tissue kallikreins. One of the inhibitors of kallikreins is a polyvalent inhibitor isolated from the lungs and salivary gland of a bull, known under the name "trasylol". It is also a trypsin inhibitor and has therapeutic use in 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 Hageman factor is a direct activator of kallikreinogen in blood plasma (see p. 641).

  Kinins have a short-term effect in the body, they are quickly inactivated. This is due to the high activity of kininases - enzymes that inactivate kinins. Kininases are found in blood plasma and in 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 actively influence the permeability of capillaries. Bradykinin in this respect is 10-15 times more active than histamine.

  There is evidence that bradykinin, increasing vascular permeability, contributes to 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 the therapeutic effect of salicylates is explained by inhibition of the formation of bradykinin. Vascular disorders characteristic of shock are also likely associated with shifts in the kinin system. The involvement of kinins in the pathogenesis of acute pancreatitis is also known.

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

  Nitrogen-free organic blood components

  The group of nitrogen-free organic substances of the blood includes carbohydrates, fats, lipoids, organic acids and some other substances. All these compounds are either products of the intermediate metabolism of carbohydrates and fats, or play the role of nutrients. The main data characterizing the content in the blood of various nitrogen-free organic substances 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 liters (if the body weight is 70 kg); 2/3 of the total amount of water falls on the intracellular fluid, 1/3 - on the extracellular fluid. Part of the extracellular water is in the vascular bed (5% of body weight), while the greater part - outside the vascular bed - is interstitial (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 terms of its quantitative and qualitative composition.

  Of the plasma cations, sodium occupies a leading position and accounts for 93% of their total amount. Among the anions, chlorine should be distinguished first of all, then bicarbonate. The sum of anions and cations is practically the same, i.e., the entire system is electrically neutral.

  Tab. 47. Ratios of concentrations of hydrogen and hydroxide ions and pH value (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 of 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 hyperhydration of the body develops. The accumulation of sodium in the blood plasma is observed with a special kidney disease, the 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 the introduction of sodium chloride solutions with the calculation of its deficiency in the extracellular space and the cell.

  • Potassium [show] .

    The concentration of K + in plasma 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 the cells is much higher than in the extracellular space, therefore, in diseases accompanied by increased cellular decay or hemolysis, the potassium content in the blood serum increases.

    Hyperkalemia is observed in acute renal failure and hypofunction of the adrenal cortex. The lack of aldosterone leads to increased excretion of sodium and water in the urine and retention of potassium in the body.

    Conversely, with increased production of aldosterone by the adrenal cortex, hypokalemia occurs. This increases the excretion of potassium in the urine, which is combined with sodium retention in the tissues. Developing hypokalemia causes severe disruption of the heart, as evidenced by ECG data. A decrease in the content of potassium in the serum is sometimes noted with the introduction of large doses of hormones of the adrenal cortex 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 coagulation, 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. Calcium in these cases comes to the plasma from the bones, which become brittle.

    An important diagnostic value is the determination of calcium in 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 seizures (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, replenishing from the muscle depot.

  • Phosphorus [show] .

    In the clinic, in the study of 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 plasma (serum) is more often used.

    Hypophosphatemia (decrease in plasma phosphorus) is especially characteristic of rickets. It is very important that a decrease in the level of inorganic phosphate in the blood plasma is noted in the early stages of the development of rickets, when clinical symptoms are not sufficiently pronounced. Hypophosphatemia is also observed with the introduction of insulin, hyperparathyroidism, osteomalacia, sprue and some other diseases.

  • Iron [show] .

    In whole blood, iron is found mainly in erythrocytes (-18.5 mmol / l), in plasma its concentration averages 0.02 mmol / l. About 25 mg of iron are released daily during the breakdown of hemoglobin in erythrocytes in the spleen and liver, and the same amount is consumed during the synthesis of hemoglobin in the cells of hematopoietic tissues. The bone marrow (the main human erythropoietic tissue) has a labile supply of iron that exceeds the daily iron requirement by 5 times. There is a much larger supply of iron in the liver and spleen (about 1000 mg, i.e., a 40-day supply). An increase in the content of iron in the blood plasma is observed with a weakening of the synthesis of hemoglobin or an increased breakdown of red blood cells.

    With anemia of various origins, the need for iron and its absorption in the intestine increase dramatically. 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 and ferritin is formed. It is assumed that the amount of iron coming from the intestine into the blood depends on the content of apoferritin in the intestinal walls. Further transport of iron from the intestine to the hematopoietic organs is carried out in the form of a complex with the blood plasma protein transferrin. The iron in this complex is in the 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 the metabolically inert hemosiderin, well known to morphologists.

    Iron deficiency in the body can cause a violation of the last stage of heme synthesis - the conversion of protoporphyrin IX to heme. As a result, anemia develops, accompanied by an increase in the content of porphyrins, in particular protoporphyrin IX, in erythrocytes.

    Minerals found in tissues, including blood, in very small amounts (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. So, plasma copper is part of ceruloplasmin, erythrocyte zinc belongs entirely to carbonic anhydrase (carbonic anhydrase), 65-76% of blood iodine is in an organically bound form - in the form of thyroxine. Thyroxine is present in the blood mainly in protein-bound form. It is complexed predominantly with its specific binding globulin, which is located during electrophoresis of serum proteins between two fractions of α-globulin. Therefore, thyroxin-binding protein is called interalphaglobulin. The cobalt found in the blood is also found in protein-bound form and only partially as a structural component of vitamin B 12 . A significant part of selenium in the blood is part of the active center of the enzyme glutathione peroxidase, and is also associated with other proteins.

  Acid-base state

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

  Taking into account the difficulty of using values ​​of the order of 0.0000001 in practical calculations, which approximately reflect the concentration of hydrogen ions, Zorenson (1909) suggested using 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 - "power of hydrogen". The concentration ratios 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 blood pH fluctuations corresponds to the state of the norm - 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 the blood. For example, in erythrocytes, the pH is 7.19 ± 0.02, differing from the pH of the 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 millionths of a millimol per 1 liter, i.e. e. make up approximately 12% of the average concentration. More significant changes in blood pH in the direction of increasing or decreasing the concentration of hydrogen ions are associated with pathological conditions.

  The 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 pH changes when acids or bases are introduced into the system, are 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 buffer systems of the blood are:

  • [show] .

    Bicarbonate buffer system- a powerful and, perhaps, the most controlled system of extracellular fluid and blood. The share of 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 in terms of 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 the 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 is very low compared to the concentration of CO 2 in blood plasma. At PCO 2 \u003d 53.3 hPa (40 mm Hg), there are approximately 500 CO 2 molecules per 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 blood plasma and the amount of carbon dioxide bound in the form of sodium bicarbonate is 1:20.

    The mechanism of the buffer action of this system is that when large amounts 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 is immediately decomposed 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 makes it possible to maintain the pH of the blood within the normal range.

    If the amount of basic ions in the blood increases, then they combine with weak carbonic acid to form bicarbonate anions and water. In order to maintain the normal ratio of the main components of the buffer system, in this case, physiological mechanisms of regulation of 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 (for example, Na 2 HP0 4). All this helps to maintain a normal ratio between the concentration of free carbon dioxide and bicarbonate in the blood.

  • Phosphate buffer system [show] .

    Phosphate buffer system is 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 performed 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 salt is dibasic phosphate (Na 2 HP0 4):

    Na 2 HP0 4 -> 2Na + + HPO 4 2- (HPO 4 2- + H + -> H 2 RO 4 -).

    For a phosphate buffer system, the following equation holds:

    

    At pH 7.4, the ratio of molar concentrations of monobasic and dibasic phosphates is 1:4.

    The buffering action of the phosphate system is based on the possibility of binding hydrogen ions by HPO 4 2- ions with the formation of 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 RO 4 - (OH - + H 4 RO 4 - -> HPO 4 2- + H 2 O).

    The phosphate buffer in the blood is closely related to the bicarbonate buffer system.

  • Protein buffer system [show] .

    Protein buffer system- quite a powerful buffer system of blood plasma. Since blood plasma proteins contain a sufficient amount of acidic and basic radicals, the buffering properties are mainly associated with the content of actively ionizable amino acid residues, monoaminodicarboxylic and diaminomonocarboxylic, in polypeptide chains. When the pH shifts to the alkaline side (remember the isoelectric point of the protein), the dissociation of the main groups is inhibited and the protein behaves like an acid (HPr). By binding a base, this acid gives a salt (NaPr). For a given buffer system, the following equation can be written:

    

    With an increase in pH, the amount of proteins in the form of a salt increases, and with a decrease, the amount of plasma proteins in the form of an 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 varies depending on its oxygen saturation. When hemoglobin is saturated with oxygen, it becomes a stronger acid (ННbO 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 HHbO 2 and KHb0 2, respectively) can be expressed by the following comparisons:

    The systems of hemoglobin and oxyhemoglobin are interconvertible systems and exist as a 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 erythrocyte hemoglobin into free HHb with the formation of an equivalent amount of bicarbonate ensures that blood pH remains within physiologically acceptable values, despite the influx of a huge amount of carbon dioxide and other acid-reactive metabolic products into the venous blood.

    Getting into the capillaries of the lungs, hemoglobin (HHb) turns into oxyhemoglobin (HHbO 2), which leads to some acidification of the blood, displacement of part of H 2 CO 3 from bicarbonates and a decrease in the alkaline reserve of blood.

    The alkaline reserve of blood - the ability of blood to bind CO 2 - is examined in the same way as the total CO 2, but under conditions of blood plasma equilibration 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, a value is obtained, which is called the reserve alkalinity of the blood. It is expressed as a percentage of CO 2 by volume (volume of CO 2 in milliliters per 100 ml of plasma). Normally, a reserve alkalinity in humans is 50-65 vol.% CO 2 .

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

  Acid-base disorders

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

  Acidosis is characterized by a concentration of hydrogen ions above normal limits. As a result, the pH naturally decreases. A drop in pH below 6.8 causes death.

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

  Depending on the mechanism of development of disorders of the acid-base state, 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 volume of breathing (for example, with bronchitis, bronchial asthma, pulmonary emphysema, mechanical asphyxia, etc.). All these diseases lead to lung hypoventilation 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 content of bicarbonate increases, i.e., the alkaline reserve of the blood increases. At the same time, the excretion with urine of free and bound in the form of ammonium salts of acids increases.

    Non-respiratory (metabolic) acidosis due to the accumulation of organic acids in the 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 illnesses. The excess accumulation of hydrogen ions in these cases is initially compensated by a decrease in the alkaline reserve of the blood. The content of CO 2 in the alveolar air is also reduced, and pulmonary ventilation is accelerated. The acidity of the urine and the concentration of ammonia in the urine are increased.

  • alkalosis [show] .

    Respiratory (gas) alkalosis occurs with a sharp increase in the respiratory function of the lungs (hyperventilation). For example, when inhaling pure oxygen, compensatory shortness of breath that accompanies a number of diseases, while 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 the urine is reduced.

    Non-respiratory (metabolic) alkalosis develops with the loss of a large number of acid equivalents (for example, indomitable 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 case of unreasonable correction metabolic acidosis. At the same time, the alkaline reserve of blood and PCO 2 in the avelveolar air increase. Pulmonary ventilation is slowed down, the acidity of urine and the content of ammonia in it are lowered (Table 48).

    Table 48. The most simple indicators of assessing the acid-base state
    Shifts (changes) in the acid-base state	Urine pH	Plasma, HCO 2 - mmol/l	Plasma, HCO 2 - mmol/l
    Norm	6-7	25	0,625
    Respiratory acidosis	reduced	raised	raised
    Respiratory alkalosis	raised	reduced	reduced
    metabolic acidosis	reduced	reduced	reduced
    metabolic alkalosis	raised	raised	raised

  In practice, isolated forms of respiratory or non-respiratory disorders are extremely rare. To clarify the nature of the disorders and the degree of compensation helps to determine the complex of indicators of the acid-base state. Over the past decades, sensitive electrodes for direct measurement of pH and PCO 2 of blood have been widely used to study indicators of the acid-base state. In clinical conditions, it is convenient to use devices such as "Astrup" or domestic devices - AZIV, AKOR. With the help of these devices and the corresponding nomograms, the following main indicators of the acid-base state can be determined:

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

  Blood functions Blood ensures the vital activity of the body and performs the following important functions: respiratory - supplies oxygen to cells from the respiratory organs and removes carbon dioxide (carbon dioxide) from them; nutritional - carries nutrients throughout the body, which in the process of digestion from the intestines enter the blood vessels; excretory - removes from the organs the decay products formed in the cells as a result of their vital activity; regulatory - transfers hormones that regulate the metabolism and work of various organs, carries out a humoral connection between organs; protective - microorganisms that have entered the blood are absorbed and neutralized by leukocytes, and 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 retains a relative constancy of composition and physicochemical properties. The constancy of the internal environment of the body - homeostasis is maintained by the continuous work of the organs of digestion, respiration, excretion. The activity of these organs is regulated by the nervous system, which reacts to changes in the external environment and ensures the alignment of shifts or disturbances in the body. In the kidneys, the blood is released from excess mineral salts, water and metabolic products, in the lungs - from carbon dioxide. If the concentration in the blood of any of the substances changes, then the neurohormonal mechanisms, regulating the activity of a number of systems, reduce or increase its excretion from the body.

  Several plasma proteins play an important role in the coagulation and anticoagulation systems.

  blood clotting- a protective reaction of the body that protects it from blood loss. People whose blood is not able 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 blood clot that clogs the wound area and stops bleeding. A blood clot is formed from the soluble protein fibrinogen, which is converted into the insoluble protein fibrin during blood clotting. The transformation 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 that are released during the destruction of platelets.

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

  When platelets are destroyed, the protein-enzyme thromboplastin is formed, which, by combining 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 process of blood coagulation, for example, vitamin K, without which the formation of prothrombin is impaired.

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

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

  The internal environment of the body

  Blood capillaries are not suitable for every cell, so the exchange of substances between cells and blood, the connection 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 education	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	Through 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)
  	Formed elements (40-50% of blood volume): erythrocytes, 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, organic and inorganic nutrients dissolved in it, O 2, CO 2, dissimilation products released from cells	The spaces between the cells of all tissues. Volume 20 l (in an adult)	Due to blood plasma and end products of dissimilation	It is an intermediate medium between blood and body cells. Transfers O 2, nutrients, mineral salts, hormones from the blood to the cells of the organs. It returns water and dissimilation products to the bloodstream through the lymph. Carries CO 2 released from cells into the bloodstream
  Lymph	Water and the decomposition products of organic matter dissolved in it	Lymphatic system, consisting of lymphatic capillaries ending in sacs and vessels that merge into two ducts that empty into the vena cava of the circulatory system in the neck	Due to tissue fluid absorbed through the sacs at the ends of the lymphatic capillaries	Return of tissue fluid to the bloodstream. Filtration and disinfection of tissue fluid, which are 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 an 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, tissue fluid is up to 20 liters; it forms the internal environment of the body. Most of this fluid returns to the blood capillaries, and a smaller part, penetrating into the lymphatic capillaries closed at one end, forms lymph.

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

  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. Thus, the connection between capillaries and cells is carried out. Carbon dioxide, water and other metabolic products formed in the cells, also due to the difference in concentrations, are released from the cells first into the tissue fluid, and then enter the capillaries. Blood from arterial becomes venous and delivers decay products to the kidneys, lungs, skin, through which they are removed from the body.

It is customary to call blood and lymph the internal environment of the body, since they surround all cells and tissues, ensuring their vital activity. In relation to its origin, blood, like other body fluids, can be considered as sea water that surrounded the simplest organisms, closed inwards and subsequently undergone certain changes and complications.

The blood is made up of plasma and being in it in a suspended state shaped elements(blood cells). In humans, the formed elements are 42.5+-5% for women and 47.5+-7% for men. This value is called hematocrit. The blood circulating in the vessels, the organs in which the formation and destruction of its cells, as well as the systems of their regulation, are united by the concept of " blood system".

All formed elements of blood are the products of vital activity not of the blood itself, but of hematopoietic tissues (organs) - red bone marrow, lymph nodes, spleen. The kinetics of blood components includes the following stages: formation, reproduction, differentiation, maturation, circulation, aging, destruction. Thus, there is an inseparable connection between the formed elements of the blood and the organs that produce and destroy them, and the cellular composition of the peripheral blood primarily reflects the state of the organs of hematopoiesis and blood destruction.

Blood, as a tissue of the internal environment, has the following features: its constituent parts are formed outside it, the interstitial substance of the tissue is liquid, the bulk of the blood is in constant motion, carrying out humoral connections in the body.

With a general tendency to maintain the constancy of its morphological and chemical composition, blood is at the same time one of the most sensitive indicators of changes occurring in the body under the influence of both various physiological conditions and pathological processes. "Blood is a mirror organism!"

Basic physiological functions of blood.

The significance of blood as the most important part of the internal environment of the body is diverse. The following main groups of blood functions can be distinguished:

1. Transport functions . These functions consist in the transfer of substances necessary for life (gases, nutrients, metabolites, hormones, enzymes, etc.) Transported substances can remain unchanged in the blood, or enter into one or another, mostly unstable, compounds with proteins, hemoglobin, other components and be transported in this state. Transport features include:

a) respiratory , consisting in the transport of oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs;

b) nutritious , which consists in the transfer of nutrients from the digestive organs to the tissues, as well as in their transfer from the depot and to the depot, depending on the need at the moment;

in) excretory (excretory ), which consists in the transfer of unnecessary metabolic products (metabolites), as well as excess salts, acid radicals and water to the places of their excretion from the body;

G) regulatory , associated with the fact that blood is the medium through which the chemical interaction of individual parts of the body with each other is carried out through hormones and other biologically active substances produced by tissues or organs.

2. Protective functions blood cells are associated with the fact that blood cells protect the body from infectious-toxic aggression. The following protective functions can be distinguished:

a) phagocytic - blood leukocytes are able to devour (phagocytize) foreign cells and foreign bodies that have entered the body;

b) immune - blood is the place where there are various kinds of antibodies that are formed in lymphocytes in response to the intake of microorganisms, viruses, toxins and provide acquired and innate immunity.

in) hemostatic (hemostasis - stopping bleeding), which consists in the ability of blood to clot at the site of injury to a blood vessel and thereby prevent fatal bleeding.

3. homeostatic functions . They consist in the participation of blood and the substances and cells in its composition in maintaining the relative constancy of a number of body constants. These include:

a) pH maintenance ;

b) maintenance of osmotic pressure;

in) temperature maintenance internal environment.

True, the latter function can also be attributed to transport, since heat is carried by circulating blood through the body from the place of its formation to the periphery and vice versa.

The amount of blood in the body. Volume of circulating blood (VCC).

Currently, there are accurate methods for determining the total amount of blood in the body. The principle of these methods is that a known amount of a substance is introduced into the blood, and then blood samples are taken at certain intervals and the content of the introduced product is determined in them. The plasma volume is calculated from the dilution obtained. After that, the blood is centrifuged in a capillary graduated pipette (hematocrit) to determine the hematocrit, i.e. ratio of formed elements and plasma. Knowing the hematocrit, it is easy to determine the volume of blood. As indicators, non-toxic, slowly excreted compounds that do not penetrate the vascular wall into tissues (dyes, polyvinylpyrrolidone, iron dextran complex, etc.) are used. Recently, radioactive isotopes have been widely used for this purpose.

Definitions show that in the vessels of a person weighing 70 kg. contains approximately 5 liters of blood, which is 7% of body weight (in men 61.5 + -8.6 ml / kg, in women - 58.9 + -4.9 ml / kg of body weight).

The introduction of fluid into the blood increases its volume for a short time. Fluid loss - reduces blood volume. However, changes in the total amount of circulating blood are usually small, due to the presence of processes that regulate the total volume of fluid in the bloodstream. The regulation of blood volume is based on maintaining a balance between the fluid in the vessels and tissues. Losses of fluid from the vessels are quickly replenished due to its intake from the tissues and vice versa. In more detail about the mechanisms of regulation of the amount of blood in the body, we will talk later.

1.Composition of blood plasma.

Plasma is a yellowish, slightly opalescent liquid, and is a very complex biological medium, which includes proteins, various salts, carbohydrates, lipids, metabolic intermediates, hormones, vitamins, and dissolved gases. It includes both organic and inorganic substances (up to 9%) and water (91-92%). Blood plasma is in close connection with the tissue fluids of the body. A large number of metabolic products enter the blood from the tissues, but, due to the complex activity of various physiological systems of the body, there are no significant changes in the composition of the plasma normally.

The amounts of proteins, glucose, all cations and bicarbonate are kept at a constant level and the slightest fluctuations in their composition lead to severe disturbances in the normal functioning of the body. At the same time, the content of substances such as lipids, phosphorus, and urea can vary significantly without causing noticeable disorders in the body. The concentration of salts and hydrogen ions in the blood is very precisely regulated.

The composition of blood plasma has some fluctuations depending on age, gender, nutrition, geographical features of the place of residence, time and season of the year.

Plasma proteins and their functions. The total content of blood proteins is 6.5-8.5%, on average -7.5%. They differ in the composition and number of amino acids they contain, solubility, stability in solution with changes in pH, temperature, salinity, and electrophoretic density. The role of plasma proteins is very diverse: they take part in the regulation of water metabolism, in protecting the body from immunotoxic effects, in the transport of metabolic products, hormones, vitamins, in blood coagulation, and in the nutrition of the body. Their exchange occurs quickly, the constancy of concentration is carried out by continuous synthesis and decay.

The most complete separation of blood plasma proteins is carried out using electrophoresis. On the electrophoregram, 6 fractions of plasma proteins can be distinguished:

Albumins. They are contained in the blood 4.5-6.7%, i.e. 60-65% of all plasma proteins are albumin. They perform mainly a nutritional-plastic function. The transport role of albumins is no less important, since they can bind and transport not only metabolites, but also drugs. With a large accumulation of fat in the blood, some of it also binds to albumin. Since albumins have a very high osmotic activity, they account for up to 80% of the total colloid-osmotic (oncotic) blood pressure. Therefore, a decrease in the amount of albumin leads to a violation of water exchange between tissues and blood and the appearance of edema. Albumin synthesis occurs in the liver. Their molecular weight is 70-100 thousand, so some of them can pass through the renal barrier and be absorbed back into the blood.

Globulins usually accompany albumins everywhere and are the most abundant of all known proteins. The total amount of globulins in plasma is 2.0-3.5%, i.e. 35-40% of all plasma proteins. By fractions, their content is as follows:

alpha1 globulins - 0.22-0.55 g% (4-5%)

alpha2 globulins- 0.41-0.71g% (7-8%)

beta globulins - 0.51-0.90 g% (9-10%)

gamma globulins - 0.81-1.75 g% (14-15%)

The molecular weight of globulins is 150-190 thousand. The place of formation may be different. Most of it is synthesized in the lymphoid and plasma cells of the reticuloendothelial system. Some are in the liver. The physiological role of globulins is diverse. So, gamma globulins are carriers of immune bodies. Alpha and beta globulins also have antigenic properties, but their specific function is participation in coagulation processes (these are plasma coagulation factors). This also includes most of the blood enzymes, as well as transferrin, ceruloplasmin, haptoglobins and other proteins.

fibrinogen. This protein is 0.2-0.4 g%, about 4% of all plasma proteins. It is directly related to coagulation, during which it precipitates after polymerization. Plasma devoid of fibrinogen (fibrin) is called blood serum.

In various diseases, especially those leading to disturbances in protein metabolism, there are sharp changes in the content and fractional composition of plasma proteins. Therefore, the analysis of blood plasma proteins is of diagnostic and prognostic value and helps the doctor to judge the degree of organ damage.

Non-protein nitrogenous substances plasma are represented by amino acids (4-10 mg%), urea (20-40 mg%), uric acid, creatine, creatinine, indican, etc. All these products of protein metabolism in total are called residual, or non-protein nitrogen. The content of residual plasma nitrogen normally ranges from 30 to 40 mg. Among the amino acids, one third is glutamine, which carries free ammonia in the blood. An increase in the amount of residual nitrogen is observed mainly in renal pathology. The amount of non-protein nitrogen in the blood plasma of men is higher than in the blood plasma of women.

Nitrogen free organic matter blood plasma is represented by such products as lactic acid, glucose (80-120 mg%), lipids, organic food substances and many others. Their total amount does not exceed 300-500 mg%.

Minerals plasma are mainly Na+, K+, Ca+, Mg++ cations and Cl-, HCO3, HPO4, H2PO4 anions. The total amount of minerals (electrolytes) in plasma reaches 1%. The number of cations exceeds the number of anions. The most important are the following minerals:

sodium and potassium . The amount of sodium in plasma is 300-350 mg%, potassium - 15-25 mg%. Sodium is found in plasma in the form of sodium chloride, bicarbonates, and also in protein-bound form. Potassium too. These ions play an important role in maintaining the acid-base balance and osmotic pressure of the blood.

Calcium . Its total amount in plasma is 8-11 mg%. It is there either in protein-bound form or in the form of ions. Ca + ions perform an important function in the processes of blood coagulation, contractility and excitability. Maintaining a normal level of calcium in the blood occurs with the participation of the hormone of the parathyroid glands, sodium - with the participation of adrenal hormones.

In addition to the minerals listed above, plasma contains magnesium, chlorides, iodine, bromine, iron, and a number of trace elements such as copper, cobalt, manganese, zinc, etc., which are of great importance for erythropoiesis, enzymatic processes, etc.

Physico-chemical properties of blood

1.Blood reaction. The active reaction of the blood is determined by the concentration of hydrogen and hydroxide ions in it. Normally, the blood has a slightly alkaline reaction (pH 7.36-7.45, on average 7.4 + -0.05). The blood reaction is a constant value. This is a prerequisite for the normal course of life processes. A change in pH by 0.3-0.4 units leads to serious consequences for the body. The boundaries of life are within the blood pH of 7.0-7.8. The body keeps the blood pH at a constant level due to the activity of a special functional system, in which the main place is given to the chemicals present in the blood itself, which, by neutralizing a significant part of the acids and alkalis entering the blood, prevent pH shifts to the acidic or alkaline side. The shift in pH to the acid side is called acidosis, into alkaline - alkalosis.

Substances that constantly enter the bloodstream and can change the pH value include lactic acid, carbonic acid and other metabolic products, substances that come with food, etc.

In the blood there are four buffer systems - bicarbonate(carbonic acid/bicarbonates), hemoglobin(hemoglobin / oxyhemoglobin), protein(acidic proteins / alkaline proteins) and phosphate(primary phosphate / secondary phosphate). Their work is studied in detail in the course of physical and colloidal chemistry.

All buffer systems of the blood, taken together, create in the blood the so-called alkaline reserve, capable of binding acidic products entering the blood. The alkaline reserve of blood plasma in a healthy body is more or less constant. It can be reduced with excessive intake or formation of acids in the body (for example, during intense muscular work, when a lot of lactic and carbonic acids are formed). If this decrease in the alkaline reserve has not yet led to real changes in the pH of the blood, then this condition is called compensated acidosis. At uncompensated acidosis the alkaline reserve is completely consumed, which leads to a decrease in pH (for example, this happens with a diabetic coma).

When acidosis is associated with the entry into the blood of acid metabolites or other products, it is called metabolic or not gas. When acidosis occurs due to the accumulation of predominantly carbon dioxide in the body, it is called gas. With excessive intake of alkaline metabolic products into the blood (more often with food, since metabolic products are mostly acidic), the alkaline reserve of the plasma increases ( compensated alkalosis). It can increase, for example, with increased hyperventilation of the lungs, when there is an excessive removal of carbon dioxide from the body (gas alkalosis). Uncompensated alkalosis happens extremely rarely.

The functional system for maintaining blood pH (FSrN) includes a number of anatomically heterogeneous organs, which in combination allow achieving a very important beneficial result for the body - ensuring a constant pH of blood and tissues. The appearance of acidic metabolites or alkaline substances in the blood is immediately neutralized by the corresponding buffer systems, and at the same time, signals from specific chemoreceptors embedded both in the walls of blood vessels and in tissues send signals to the central nervous system about the occurrence of a shift in blood reactions (if one actually occurred). In the intermediate and oblong parts of the brain there are centers that regulate the constancy of the reaction of the blood. From there, along the afferent nerves and through the humoral channels, commands are sent to the executive organs that can correct the violation of homeostasis. These organs include all excretory organs (kidneys, skin, lungs), which eject from the body both the acidic products themselves and the products of their reactions with buffer systems. In addition, the organs of the gastrointestinal tract take part in the activity of the FSR, which can be both a place for the release of acidic products and a place from which the substances necessary for their neutralization are absorbed. Finally, the liver, where potentially harmful products, both acidic and alkaline, are detoxified, is also among the executive organs of the FSR. It should be noted that in addition to these internal organs, the FSR also has an external link - a behavioral one, when a person purposefully searches in the external environment for substances that he lacks to maintain homeostasis (“I want sour!”). The scheme of this FS is presented in the diagram.

2. Specific gravity of blood ( SW). Blood pressure depends mainly on the number of erythrocytes, the hemoglobin contained in them and the protein composition of the plasma. In men, it is 1.057, in women - 1.053, which is explained by the different content of red blood cells. Daily fluctuations do not exceed 0.003. An increase in HC is naturally observed after physical exertion and under conditions of exposure to high temperatures, which indicates some thickening of the blood. The decrease in HC after blood loss is associated with a large influx of fluid from the tissues. The most common method of determination is copper sulfate, the principle of which is to place a drop of blood in a series of test tubes with solutions of copper sulfate of a known specific gravity. Depending on the HC of the blood, the drop sinks, floats or floats in the place of the test tube where it was placed.

3. Osmotic properties of blood. Osmosis is the penetration of solvent molecules into a solution through a semi-permeable membrane separating them, through which solutes do not pass. Osmosis also occurs if such a partition separates solutions with different concentrations. In this case, the solvent moves through the membrane towards the solution with a higher concentration until these concentrations are equal. The measure of osmotic forces is osmotic pressure (OD). It is equal to such a hydrostatic pressure, which must be applied to the solution in order to stop the penetration of solvent molecules into it. This value is determined not by the chemical nature of the substance, but by the number of dissolved particles. It is directly proportional to the molar concentration of the substance. A one-molar solution has an OD of 22.4 atm., since the osmotic pressure is determined by the pressure that a solute can exert in an equal volume in the form of a gas (1 gM of gas occupies a volume of 22.4 liters. If this amount of gas is placed in a vessel with a volume of 1 liter, it will press on the walls with a force of 22.4 atm.).

Osmotic pressure should be considered not as a property of a solute, solvent or solution, but as a property of a system consisting of a solution, a solute and a semipermeable membrane separating them.

The blood is just such a system. The role of a semi-permeable partition in this system is played by the shells of blood cells and the walls of blood vessels, the solvent is water, in which there are mineral and organic substances in dissolved form. These substances create an average molar concentration in the blood of about 0.3 gM, and therefore develop an osmotic pressure equal to 7.7 - 8.1 atm for human blood. Almost 60% of this pressure is due to table salt (NaCl).

The value of the osmotic pressure of the blood is of great physiological importance, since in a hypertonic environment water leaves the cells ( plasmolysis), and in hypotonic - on the contrary, enters the cells, inflates them and can even destroy ( hemolysis).

True, hemolysis can occur not only when the osmotic balance is disturbed, but also under the influence of chemicals - hemolysins. These include saponins, bile acids, acids and alkalis, ammonia, alcohols, snake venom, bacterial toxins, etc.

The value of the osmotic pressure of blood is determined by the cryoscopic method, i.e. freezing point of blood. In humans, the plasma freezing point is -0.56-0.58°C. The osmotic pressure of human blood corresponds to the pressure of 94% NaCl, such a solution is called physiological.

In the clinic, when it becomes necessary to introduce fluid into the blood, for example, when the body is dehydrated, or when administering drugs intravenously, this solution, which is isotonic to blood plasma, is usually used. However, although it is called physiological, it is not such in the strict sense, since it lacks the rest of the mineral and organic substances. More physiological solutions are such as Ringer's solution, Ringer-Locke, Tyrode, Kreps-Ringer's solution, and the like. They approach blood plasma in ionic composition (isoionic). In some cases, especially to replace plasma in case of blood loss, blood substitute fluids are used that approach plasma not only in mineral, but also in protein, macromolecular composition.

The fact is that blood proteins play an important role in the proper water exchange between tissues and plasma. The osmotic pressure of blood proteins is called oncotic pressure. It is equal to approximately 28 mm Hg. those. is less than 1/200 of the total osmotic pressure of the plasma. But since the capillary wall is very little permeable to proteins and easily permeable to water and crystalloids, it is the oncotic pressure of proteins that is the most effective factor that retains water in the blood vessels. Therefore, a decrease in the amount of proteins in the plasma leads to the appearance of edema, to the release of water from the vessels into the tissues. Of the blood proteins, albumins develop the highest oncotic pressure.

Functional osmotic pressure regulation system. The osmotic blood pressure of mammals and humans is normally kept at a relatively constant level (Hamburger's experiment with the introduction of 7 liters of 5% sodium sulfate solution into the horse's blood). All this happens due to the activity of the functional system of regulation of osmotic pressure, which is closely linked to the functional system of regulation of water-salt homeostasis, since it uses the same executive organs.

The walls of blood vessels contain nerve endings that respond to changes in osmotic pressure ( osmoreceptors). Their irritation causes excitation of the central regulatory formations in the medulla oblongata and diencephalon. From there come commands that include certain organs, such as the kidneys, which remove excess water or salts. Of the other executive organs of the FSOD, it is necessary to name the organs of the digestive tract, in which both the excretion of excess salts and water and the absorption of the products necessary for the restoration of OD occur; skin, the connective tissue of which absorbs excess water with a decrease in osmotic pressure or gives it to the latter with an increase in osmotic pressure. In the intestines, solutions of mineral substances are absorbed only in such concentrations that contribute to the establishment of normal osmotic pressure and the ionic composition of the blood. Therefore, when taking hypertonic solutions (epsom salts, sea water), dehydration occurs due to the removal of water into the intestinal lumen. The laxative effect of salts is based on this.

The factor that can change the osmotic pressure of tissues, as well as blood, is metabolism, because the cells of the body consume large-molecular nutrients, and in return release a much larger number of molecules of low-molecular products of their metabolism. From this it is clear why venous blood flowing from the liver, kidneys, muscles has a greater osmotic pressure than arterial blood. It is no coincidence that these organs contain the largest number of osmoreceptors.

Particularly significant shifts in osmotic pressure in the whole organism are caused by muscular work. With very intensive work, the activity of the excretory organs may not be sufficient to maintain the osmotic pressure of the blood at a constant level, and as a result, its increase may occur. A shift in the osmotic pressure of the blood to 1.155% NaCl makes it impossible to continue work (one of the components of fatigue).

4. Suspension properties of blood. Blood is a stable suspension of small cells in a liquid (plasma). The property of blood as a stable suspension is violated when the blood passes to a static state, which is accompanied by cell sedimentation and is most clearly manifested by erythrocytes. The noted phenomenon is used to assess the suspension stability of blood in determining the erythrocyte sedimentation rate (ESR).

If the blood is prevented from clotting, then the formed elements can be separated from the plasma by simple settling. This is of practical clinical importance, since ESR changes markedly in some conditions and diseases. So, ESR is greatly accelerated in women during pregnancy, in patients with tuberculosis, and in inflammatory diseases. When blood stands, erythrocytes stick together (agglutinate), forming the so-called coin columns, and then conglomerates of coin columns (aggregation), which settle the faster, the larger their size.

Aggregation of erythrocytes, their adhesion depends on changes in the physical properties of the surface of erythrocytes (possibly with a change in the sign of the total charge of the cell from negative to positive), as well as on the nature of the interaction of erythrocytes with plasma proteins. The suspension properties of blood depend mainly on the protein composition of the plasma: an increase in the content of coarsely dispersed proteins during inflammation is accompanied by a decrease in suspension stability and an acceleration of ESR. The ESR value also depends on the quantitative ratio of plasma and erythrocytes. In newborns, ESR is 1-2 mm/hour, in men 4-8 mm/hour, in women 6-10 mm/hour. ESR is determined by the Panchenkov method (see workshop).

Accelerated ESR, due to changes in plasma proteins, especially during inflammation, also corresponds to increased aggregation of erythrocytes in capillaries. The predominant aggregation of erythrocytes in the capillaries is associated with a physiological slowdown in blood flow in them. It has been proven that under conditions of slow blood flow, an increase in the content of coarsely dispersed proteins in the blood leads to a more pronounced cell aggregation. The aggregation of erythrocytes, reflecting the dynamism of the suspension properties of blood, is one of the oldest defense mechanisms. In invertebrates, erythrocyte aggregation plays a leading role in the processes of hemostasis; during an inflammatory reaction, this leads to the development of stasis (stopping blood flow in the border areas), contributing to the delimitation of the focus of inflammation.

Recently, it has been proven that in ESR it is not so much the charge of erythrocytes that matters, but the nature of its interaction with the hydrophobic complexes of the protein molecule. The theory of erythrocyte charge neutralization by proteins has not been proven.

5.Blood viscosity(rheological properties of blood). The viscosity of blood, determined outside the body, exceeds the viscosity of water by 3-5 times and depends mainly on the content of erythrocytes and proteins. The influence of proteins is determined by the structural features of their molecules: fibrillar proteins increase viscosity to a much greater extent than globular ones. The pronounced effect of fibrinogen is associated not only with high internal viscosity, but is also due to the aggregation of erythrocytes caused by it. Under physiological conditions, in vitro blood viscosity increases (up to 70%) after strenuous physical work and is a consequence of changes in the colloidal properties of blood.

In vivo, blood viscosity is characterized by significant dynamism and varies depending on the length and diameter of the vessel and blood flow velocity. Unlike homogeneous liquids, the viscosity of which increases with a decrease in the diameter of the capillary, the opposite is noted on the part of the blood: in the capillaries, the viscosity decreases. This is due to the heterogeneity of the structure of blood, as a liquid, and a change in the nature of the flow of cells through vessels of different diameters. So, the effective viscosity, measured by special dynamic viscometers, is as follows: aorta - 4.3; small artery - 3.4; arterioles - 1.8; capillaries - 1; venules - 10; small veins - 8; veins 6.4. It has been shown that if blood viscosity were a constant value, then the heart would have to develop 30-40 times more power to push blood through the vascular system, since viscosity is involved in the formation of peripheral resistance.

The decrease in blood clotting under conditions of heparin administration is accompanied by a decrease in viscosity and, at the same time, an acceleration of blood flow velocity. It has been shown that blood viscosity always decreases with anemia, increases with polycythemia, leukemia, and some poisonings. Oxygen lowers blood viscosity, so venous blood is more viscous than arterial blood. As the temperature rises, the viscosity of the blood decreases.

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Ministry of Education and Science of the Russian Federation

Tyumen State University

Institute of Biology

Composition and functions of blood

Tyumen 2015

Introduction

Blood is a red liquid, slightly alkaline reaction, salty taste with a specific gravity of 1.054-1.066. The total amount of blood in an adult averages about 5 liters (equal to 1/13 of body weight by weight). 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 are the following:

Transport of nutrients from the digestive tract to tissues, places of reserve reserves from them (trophic function);

Transport of metabolic end products from tissues to excretory organs (excretory function);

Transport of gases (oxygen and carbon dioxide from the respiratory organs to the tissues and back; oxygen storage (respiratory function);

Transport of hormones from endocrine glands to organs (humoral regulation);

Protective function - is carried out due to the phagocytic activity of leukocytes (cellular immunity), the production of antibodies by lymphocytes that neutralize genetically alien substances (humoral immunity);

Blood clotting that prevents blood loss;

Thermoregulatory function - redistribution of heat between organs, regulation of heat transfer through the skin;

Mechanical function - giving turgor tension to the organs due to the rush of blood to them; ensuring ultrafiltration in the capillaries of the capsules of the nephron of the kidneys, etc.;

Homeostatic function - maintaining the constancy of the internal environment of the body, suitable for cells in terms of ionic composition, concentration of hydrogen ions, etc.

Blood, as a liquid tissue, ensures the constancy of the internal environment of the body. Biochemical indicators of blood occupy a special place and are very important both for assessing the physiological status of the body and for the timely diagnosis of pathological conditions. Blood provides the interconnection of metabolic processes occurring in various organs and tissues, performs various functions.

The relative constancy of the composition and properties of blood is a necessary and indispensable condition for the vital activity of all body tissues. In humans and warm-blooded animals, the metabolism in cells, between cells and tissue fluid, as well as between tissues (tissue fluid) and blood occurs normally, provided that the internal environment of the body (blood, tissue fluid, lymph) is relatively constant.

In diseases, various changes in metabolism in cells and tissues and related changes in the composition and properties of blood are observed. By the nature of these changes, one can to a certain extent judge the disease itself.

Blood consists of plasma (55-60%) and shaped elements suspended in it - erythrocytes (39-44%), leukocytes (1%) and platelets (0.1%). Due to the presence of proteins and red blood cells in the blood, its viscosity is 4-6 times higher than the viscosity of water. When blood is standing in a test tube or centrifuged at low speeds, its formed elements are deposited.

Spontaneous precipitation of blood cells is called the erythrocyte sedimentation reaction (ROE, now - ESR). The ESR value (mm/h) for different animal species varies widely: if for a dog the ESR practically coincides with the range of values ​​for a human (2-10 mm/h), then for a pig and a horse it does not exceed 30 and 64, respectively. Blood plasma devoid of the fibrinogen protein is called blood serum.

blood plasma hemoglobin anemia

1. Chemical composition of blood

What is the composition of human blood? Blood is one of the tissues of the body, consisting of plasma (the liquid part) and cellular elements. Plasma is a homogeneous transparent or slightly cloudy liquid with a yellow tint, which is the intercellular substance of blood tissues. Plasma consists of water in which substances (mineral and organic) are dissolved, including proteins (albumins, globulins and fibrinogen). Carbohydrates (glucose), fats (lipids), hormones, enzymes, vitamins, individual constituents of salts (ions) and some metabolic products.

Together with plasma, the body removes metabolic products, various poisons and antigen-antibody immune complexes (which occur when foreign particles enter the body as a protective reaction to remove them) and all unnecessary that interferes with the body's work.

Composition of blood: blood cells

The cellular elements of the blood are also heterogeneous. They consist of:

erythrocytes (red blood cells);

leukocytes (white blood cells);

platelets (platelets).

Erythrocytes are red blood cells. They transport oxygen from the lungs to all human organs. It is erythrocytes that contain iron-containing protein - bright red hemoglobin, which attaches oxygen from the inhaled air to itself in the lungs, after which it gradually transfers it to all organs and tissues of various parts of the body.

Leukocytes are white blood cells. Responsible for immunity, i.e. for the ability of the human body to resist various viruses and infections. There are different types of leukocytes. Some of them are aimed directly at the destruction of bacteria or various foreign cells that have entered the body. Others are involved in the production of special molecules, the so-called antibodies, which are also necessary to fight various infections.

Platelets are platelets. They help the body stop bleeding, that is, they regulate blood clotting. For example, if you damage a blood vessel, then a blood clot will appear at the site of damage over time, after which a crust will form, respectively, the bleeding will stop. Without platelets (and with them a number of substances that are found in blood plasma), clots will not form, so any wound or nosebleed, for example, can lead to a large loss of blood.

Blood composition: normal

As we wrote above, there are red blood cells and white blood cells. So, normally, erythrocytes (red blood cells) in men should be 4-5 * 1012 / l, in women 3.9-4.7 * 1012 / l. Leukocytes (white blood cells) - 4-9 * 109 / l of blood. In addition, in 1 µl of blood there are 180-320 * 109 / l of platelets (platelets). Normally, the volume of cells is 35-45% of the total blood volume.

The chemical composition of human blood

Blood washes every cell of the human body and every organ, therefore it reacts to any changes in the body or lifestyle. Factors affecting the composition of the blood are quite diverse. Therefore, in order to correctly read the results of the tests, the doctor needs to know about bad habits and physical activity of a person, and even about the diet. Even the environment and that affects the composition of the blood. Everything related to metabolism also affects blood counts. For example, consider how a regular meal changes blood counts:

Eating before a blood test to increase the concentration of fat.

Fasting for 2 days will increase bilirubin in the blood.

Fasting more than 4 days will reduce the amount of urea and fatty acids.

Fatty foods will increase your potassium and triglyceride levels.

Eating too much meat will increase your urate levels.

Coffee increase the level of glucose, fatty acids, leukocytes and erythrocytes.

The blood of smokers differs significantly from the blood of people leading a healthy lifestyle. However, if you lead an active lifestyle, before taking a blood test, you need to reduce the intensity of training. This is especially true when it comes to hormone testing. Various medications also affect the chemical composition of the blood, so if you have taken something, be sure to tell your doctor about it.

2. Blood plasma

Blood plasma is the liquid part of the blood, in which the formed elements (blood cells) are suspended. Plasma is a viscous protein liquid of a slightly yellowish color. Plasma contains 90-94% water and 7-10% organic and inorganic substances. Blood plasma interacts with the tissue fluid of the body: all substances necessary for life pass from plasma to tissues, and back - metabolic products.

Blood plasma makes up 55-60% of the total blood volume. It contains 90-94% water and 7-10% dry matter, in which 6-8% is accounted for by protein substances, and 1.5-4% by other organic and mineral compounds. Water serves as a source of water for the cells and tissues of the body, maintains blood pressure and blood volume. Normally, the concentrations of some solutes in the blood plasma remain constant all the time, while the content of others may fluctuate within certain limits, depending on the rate of their entry into the blood or removal from it.

Plasma composition

Plasma contains:

organic substances - blood proteins: albumins, globulins and fibrinogen

glucose, fat and fat-like substances, amino acids, various metabolic products (urea, uric acid, etc.), as well as enzymes and hormones

inorganic substances (salts of sodium, potassium, calcium, etc.) make up about 0.9-1.0% of blood plasma. At the same time, the concentration of various salts in plasma is approximately constant.

minerals, especially sodium and chloride ions. They play a major role in maintaining the relative constancy of the osmotic pressure of the blood.

Blood proteins: albumin

One of the main components of blood plasma is various types of proteins, which are formed mainly in the liver. Plasma proteins, together with the rest of the blood components, maintain a constant concentration of hydrogen ions at a slightly alkaline level (pH 7.39), which is vital for most biochemical processes in the body.

According to the shape and size of the molecules, blood proteins are divided into albumins and globulins. The most common blood plasma protein is albumin (more than 50% of all proteins, 40-50 g/l). They act as transport proteins for certain hormones, free fatty acids, bilirubin, various ions and drugs, maintain the constancy of the colloid osmotic constancy of the blood, and participate in a number of metabolic processes in the body. Albumin synthesis occurs in the liver.

The content of albumin in the blood serves as an additional diagnostic sign in a number of diseases. With a low concentration of albumin in the blood, the balance between blood plasma and intercellular fluid is disturbed. The latter ceases to flow into the blood, and edema occurs. The concentration of albumin can decrease both with a decrease in its synthesis (for example, with impaired absorption of amino acids), and with an increase in albumin losses (for example, through an ulcerated mucosa of the gastrointestinal tract). In senile and advanced age, the content of albumin decreases. Measurement of plasma albumin concentration is used as a test of liver function, since chronic liver diseases are characterized by low albumin concentrations due to a decrease in its synthesis and an increase in the volume of distribution as a result of fluid retention in the body.

Low albumin (hypoalbuminaemia) in newborns increases the risk of jaundice because albumin binds free bilirubin in the blood. Albumin also binds many drugs that enter the bloodstream, so when its concentration decreases, the risk of poisoning by an unbound substance increases. Analbuminemia is a rare hereditary disorder in which the plasma albumin concentration is very low (250 mg/l or less). Individuals with these disorders are prone to occasional mild edema without any other clinical symptoms. A high concentration of albumin in the blood (hyperalbuminemia) can be caused either by an excess infusion of albumin or by dehydration (dehydration) of the body.

Immunoglobulins

Most other plasma proteins are globulins. Among them, there are: a-globulins that bind thyroxine and bilirubin; b-globulins that bind iron, cholesterol and vitamins A, D and K; g-globulins that bind histamine and play an important role in the immunological reactions of the body, therefore they are otherwise called immunoglobulins or antibodies. There are 5 main classes of immunoglobulins, the most common of which are IgG, IgA, IgM. The decrease and increase in the concentration of immunoglobulins in the blood plasma can be both physiological and pathological. Various hereditary and acquired disorders of immunoglobulin synthesis are known. A decrease in their number often occurs with malignant blood diseases, such as chronic lymphatic leukemia, multiple myeloma, Hodgkin's disease; may be due to the use of cytotoxic drugs or with significant protein losses (nephrotic syndrome). In the complete absence of immunoglobulins, such as in AIDS, recurrent bacterial infections may develop.

Elevated concentrations of immunoglobulins are observed in acute and chronic infectious, as well as autoimmune diseases, for example, rheumatism, systemic lupus erythematosus, etc. Significant assistance in diagnosing many infectious diseases is provided by the detection of immunoglobulins to specific antigens (immunodiagnostics).

Other plasma proteins

In addition to albumins and immunoglobulins, blood plasma contains a number of other proteins: complement components, various transport proteins, such as thyroxin-binding globulin, sex hormone-binding globulin, transferrin, etc. The concentrations of some proteins increase during an acute inflammatory reaction. Among them are known antitrypsins (protease inhibitors), C-reactive protein and haptoglobin (a glycopeptide that binds free hemoglobin). Measurement of C-reactive protein concentration helps to monitor the course of diseases characterized by episodes of acute inflammation and remission, such as rheumatoid arthritis. Hereditary deficiency of a1-antitrypsin can cause hepatitis in newborns. A decrease in plasma haptoglobin concentration indicates an increase in intravascular hemolysis, and is also noted in chronic liver diseases, severe sepsis and metastatic disease.

Globulins include plasma proteins involved in blood coagulation, such as prothrombin and fibrinogen, and determination of their concentration is important when examining patients with bleeding.

Fluctuations in the concentration of proteins in plasma are determined by the rate of their synthesis and removal and the volume of their distribution in the body, for example, when changing the position of the body (within 30 minutes after moving from a supine position to a vertical position, the concentration of proteins in the plasma increases by 10-20%) or after applying tourniquet for venipuncture (protein concentration may increase within a few minutes). In both cases, an increase in the concentration of proteins is caused by an increase in the diffusion of fluid from the vessels into the intercellular space, and a decrease in the volume of their distribution (the effect of dehydration). In contrast, a rapid decrease in protein concentration is most often the result of an increase in plasma volume, for example, with an increase in capillary permeability in patients with generalized inflammation.

Other plasma substances

Blood plasma contains cytokines - low molecular weight peptides (less than 80 kD) involved in the processes of inflammation and immune response. Determination of their concentration in the blood is used for early diagnosis of sepsis and rejection reactions of transplanted organs.

In addition, blood plasma contains nutrients (carbohydrates, fats), vitamins, hormones, enzymes involved in metabolic processes. The waste products of the body to be removed, such as urea, uric acid, creatinine, bilirubin, etc., enter the blood plasma. They are transferred to the kidneys with the blood stream. The concentration of waste products in the blood has its own acceptable limits. An increase in the concentration of uric acid can be observed with gout, the use of diuretics, as a result of a decrease in kidney function, etc., a decrease in acute hepatitis, treatment with allopurinol, etc. An increase in the concentration of urea in the blood plasma is observed with renal failure, acute and chronic nephritis, with shock, etc., a decrease in liver failure, nephrotic syndrome, etc.

The blood plasma also contains mineral substances - salts of sodium, potassium, calcium, magnesium, chlorine, phosphorus, iodine, zinc, etc., the concentration of which is close to the concentration of salts in sea water, where the first multicellular creatures first appeared millions of years ago. Plasma minerals are jointly involved in the regulation of osmotic pressure, blood pH, and in a number of other processes. For example, calcium ions affect the colloidal state of cellular contents, are involved in the process of blood clotting, in the regulation of muscle contraction and the sensitivity of nerve cells. Most salts in blood plasma are associated with proteins or other organic compounds.

3. Formed elements of blood

blood cells

Platelets (from thrombus and Greek kytos - receptacle, here - cell), blood cells of vertebrates containing a nucleus (except mammals). Participate in blood clotting. Mammalian and human platelets, called platelets, are round or oval flattened cell fragments 3–4 µm in diameter, surrounded by a membrane and usually lacking a nucleus. They contain a large number of mitochondria, elements of the Golgi complex, ribosomes, as well as granules of various shapes and sizes containing glycogen, enzymes (fibronectin, fibrinogen), platelet growth factor, etc. Platelets are formed from large bone marrow cells called megakaryocytes. Two-thirds of platelets circulate in the blood, the rest are deposited in the spleen. 1 µl of human blood contains 200-400 thousand platelets.

When a vessel is damaged, platelets become activated, become spherical and acquire the ability to adhere - stick to the vessel wall, and to aggregate - stick to each other. The resulting thrombus restores the integrity of the walls of the vessel. An increase in the number of platelets can accompany chronic inflammatory processes (rheumatoid arthritis, tuberculosis, colitis, enteritis, etc.), as well as acute infections, hemorrhages, hemolysis, anemia. A decrease in the number of platelets is observed with leukemia, aplastic anemia, with alcoholism, etc. Dysfunction of platelets may be due to genetic or external factors. Genetic defects underlie von Willebrand disease and a number of other rare syndromes. The lifespan of human platelets is 8 days.

Erythrocytes (red blood cells; from the Greek erythros - red and kytos - receptacle, here - cell) - highly specific blood cells of animals and humans containing hemoglobin.

The diameter of an individual erythrocyte is 7.2-7.5 microns, the thickness is 2.2 microns, and the volume is about 90 microns3. The total surface of all erythrocytes reaches 3000 m2, which is 1500 times the surface of the human body. Such a large surface of erythrocytes is due to their large number and peculiar shape. They have the shape of a biconcave disc and, when cross-sectioned, resemble dumbbells. With this shape, there is not a single point in erythrocytes that would be more than 0.85 microns from the surface. Such ratios of surface and volume contribute to the optimal performance of the main function of erythrocytes - the transfer of oxygen from the respiratory organs to the cells of the body.

Functions of red blood cells

Red blood cells carry oxygen from the lungs to the tissues and carbon dioxide from the tissues to the respiratory organs. The dry matter of a human erythrocyte contains about 95% hemoglobin and 5% other substances - proteins and lipids. In humans and mammals, erythrocytes lack a nucleus and are shaped like biconcave discs. The specific shape of erythrocytes results in a higher surface to volume ratio, which increases the possibility of gas exchange. In sharks, frogs, and birds, erythrocytes are oval or round in shape and contain nuclei. The average diameter of human erythrocytes is 7-8 microns, which is approximately equal to the diameter of blood capillaries. The erythrocyte is able to "fold" when passing through the capillaries, the lumen of which is less than the diameter of the erythrocyte.

red blood cells

In the capillaries of the lung alveoli, where the oxygen concentration is high, hemoglobin combines with oxygen, and in metabolically active tissues, where the oxygen concentration is low, oxygen is released and diffuses from the erythrocyte into the surrounding cells. The percentage of blood oxygen saturation depends on the partial pressure of oxygen in the atmosphere. The affinity of ferrous iron, which is part of hemoglobin, for carbon monoxide (CO) is several hundred times greater than its affinity for oxygen, therefore, in the presence of even a very small amount of carbon monoxide, hemoglobin primarily binds to CO. After inhalation of carbon monoxide, a person quickly collapses and can die from suffocation. Hemoglobin also transports carbon dioxide. The enzyme carbonic anhydrase contained in erythrocytes also participates in its transport.

Hemoglobin

Human erythrocytes, like all mammals, have the shape of a biconcave disk and contain hemoglobin.

Hemoglobin is the main component of erythrocytes and provides the respiratory function of the blood, being a respiratory pigment. It is located inside the red blood cells, and not in the blood plasma, which provides a decrease in blood viscosity and prevents the body from losing hemoglobin due to its filtration in the kidneys and excretion in the urine.

According to the chemical structure, hemoglobin consists of 1 molecule of the protein globin and 4 molecules of the iron-containing heme compound. The heme iron atom is able to attach and donate an oxygen molecule. In this case, the valence of iron does not change, i.e., it remains divalent.

The blood of healthy men contains an average of 14.5 g% of hemoglobin (145 g/l). This value can vary from 13 to 16 (130-160 g/l). The blood of healthy women contains an average of 13 g of hemoglobin (130 g/l). This value can range from 12 to 14.

Hemoglobin is synthesized by cells in the bone marrow. With the destruction of red blood cells after heme cleavage, hemoglobin is converted into the bile pigment bilirubin, which enters the intestine with bile and, after transformations, is excreted in the feces.

Normally, hemoglobin is contained in the form of 2 physiological compounds.

Hemoglobin, which has added oxygen, turns into oxyhemoglobin - HbO2. This compound is different in color from hemoglobin, so arterial blood has a bright scarlet color. Oxyhemoglobin, which has given up oxygen, is called reduced - Hb. It is found in venous blood, which is darker in color than arterial blood.

Hemoglobin already appears in some annelids. With its help, gas exchange is carried out in fish, amphibians, reptiles, birds, mammals and humans. In the blood of some mollusks, crustaceans, and others, oxygen is carried by a protein molecule, hemocyanin, which contains not iron, but copper. In some annelids, oxygen transfer is carried out using hemerythrin or chlorocruorin.

Formation, destruction and pathology of erythrocytes

The process of formation of red blood cells (erythropoiesis) occurs in the red bone marrow. Immature erythrocytes (reticulocytes) entering the bloodstream from the bone marrow contain cell organelles - ribosomes, mitochondria and the Golgi apparatus. Reticulocytes make up about 1% of all circulating erythrocytes. Their final differentiation occurs within 24-48 hours after entering the bloodstream. The rate of decay of erythrocytes and their replacement with new ones depends on many conditions, in particular, on the oxygen content in the atmosphere. Low oxygen levels in the blood stimulate the bone marrow to produce more red blood cells than are destroyed in the liver. At a high oxygen content, the opposite picture is observed.

The blood of men contains an average of 5x1012 / l of erythrocytes (6,000,000 in 1 μl), in women - about 4.5x1012 / l (4,500,000 in 1 μl). Such a number of erythrocytes, laid in a chain, will circle the globe 5 times along the equator.

A higher content of erythrocytes in men is associated with the influence of male sex hormones - androgens, which stimulate the formation of erythrocytes. The number of red blood cells varies depending on age and health status. An increase in the number of red blood cells is most often associated with oxygen starvation of tissues or with pulmonary diseases, congenital heart defects, it can occur when smoking, impaired erythropoiesis due to a tumor or cyst. A decrease in the number of red blood cells is a direct indication of anemia (anemia). In advanced cases, with a number of anemias, there is a heterogeneity of erythrocytes in size and shape, in particular, with iron deficiency anemia in pregnant women.

Sometimes a ferric atom is included in the heme instead of a divalent one, and methemoglobin is formed, which binds oxygen so tightly that it is not able to give it to the tissues, resulting in oxygen starvation. The formation of methemoglobin in erythrocytes can be hereditary or acquired - as a result of exposure of erythrocytes to strong oxidizing agents, such as nitrates, some drugs - sulfonamides, local anesthetics (lidocaine).

The lifespan of red blood cells in adults is about 3 months, after which they are destroyed in the liver or spleen. Every second, from 2 to 10 million red blood cells are destroyed in the human body. The aging of erythrocytes is accompanied by a change in their shape. In the peripheral blood of healthy people, the number of regular erythrocytes (discocytes) is 85% of their total number.

Hemolysis is the destruction of the erythrocyte membrane, accompanied by the release of hemoglobin from them into the blood plasma, which turns red and becomes transparent.

Hemolysis can occur both as a result of internal cell defects (for example, with hereditary spherocytosis), and under the influence of adverse microenvironmental factors (for example, toxins of an inorganic or organic nature). During hemolysis, the contents of the erythrocyte are released into the blood plasma. Extensive hemolysis leads to a decrease in the total number of red blood cells circulating in the blood (hemolytic anemia).

Under natural conditions, in some cases, the so-called biological hemolysis can be observed, which develops during the transfusion of incompatible blood, with the bites of some snakes, under the influence of immune hemolysins, etc.

During aging of the erythrocyte, its protein components are broken down into their constituent amino acids, and the iron that was part of the heme is retained by the liver and can later be reused in the formation of new erythrocytes. The rest of the heme is cleaved to form the bile pigments bilirubin and biliverdin. Both pigments are eventually excreted in the bile into the intestines.

Erythrocyte sedimentation rate (ESR)

If anticoagulants are added to a test tube with blood, then its most important indicator can be studied - the erythrocyte sedimentation rate. To study the ESR, blood is mixed with a solution of sodium citrate and collected in a glass tube with millimeter divisions. An hour later, the height of the upper transparent layer is counted.

Erythrocyte sedimentation is normal in men is 1-10 mm per hour, in women - 2-5 mm per hour. An increase in the sedimentation rate above the indicated values ​​is a sign of pathology.

The value of ESR depends on the properties of the plasma, primarily on the content of large molecular proteins in it - globulins and especially fibrinogen. The concentration of the latter increases in all inflammatory processes, therefore, in such patients, the ESR usually exceeds the norm.

In the clinic, the erythrocyte sedimentation rate (ESR) is used to judge the state of the human body. Normal ESR in men is 1-10 mm/hour, in women 2-15 mm/hour. An increase in ESR is a highly sensitive, but non-specific test for an actively ongoing inflammatory process. With a reduced number of red blood cells in the blood, the ESR increases. A decrease in ESR is observed with various erythrocytosis.

Leukocytes (white blood cells are colorless blood cells of humans and animals. All types of leukocytes (lymphocytes, monocytes, basophils, eosinophils and neutrophils) are spherical in shape, have a nucleus and are capable of active amoeboid movement. Leukocytes play an important role in protecting the body from diseases - - produce antibodies and absorb bacteria.1 µl of blood normally contains 4-9 thousand leukocytes.The number of leukocytes in the blood of a healthy person is subject to fluctuations: it increases by the end of the day, with physical exertion, emotional stress, protein intake, a sharp change in temperature environment.

There are two main groups of leukocytes - granulocytes (granular leukocytes) and agranulocytes (non-granular leukocytes). Granulocytes are subdivided into neutrophils, eosinophils and basophils. All granulocytes have a lobed nucleus and granular cytoplasm. Agranulocytes are divided into two main types: monocytes and lymphocytes.

Neutrophils

Neutrophils make up 40-75% of all leukocytes. The diameter of the neutrophil is 12 microns, the nucleus contains from two to five lobules interconnected by thin filaments. Depending on the degree of differentiation, stab (immature forms with horseshoe-shaped nuclei) and segmented (mature) neutrophils are distinguished. In women, one of the segments of the nucleus contains an outgrowth in the form of a drumstick - the so-called Barr's body. The cytoplasm is filled with many small granules. Neutrophils contain mitochondria and a large amount of glycogen. The life span of neutrophils is about 8 days. The main function of neutrophils is the detection, capture (phagocytosis) and digestion with the help of hydrolytic enzymes of pathogenic bacteria, tissue fragments and other material to be removed, the specific recognition of which is carried out using receptors. After phagocytosis, neutrophils die, and their remains form the main component of pus. Phagocytic activity, most pronounced at the age of 18-20 years, decreases with age. The activity of neutrophils is stimulated by many biologically active compounds - platelet factors, metabolites of arachidonic acid, etc. Many of these substances are chemoattractants, along the concentration gradient of which neutrophils migrate to the site of infection (see Taxis). By changing their shape, they can squeeze between endothelial cells and leave the blood vessel. The release of the contents of neutrophil granules, toxic to tissues, in places of their massive death can lead to the formation of extensive local lesions (see Inflammation).

Eosinophils

Basophils

Basophils make up 0-1% of the leukocyte population. Size 10-12 microns. More often they have a tripartite S-shaped nucleus, contain all types of organelles, free ribosomes and glycogen. Cytoplasmic granules are stained blue with basic dyes (methylene blue, etc.), which is the reason for the name of these leukocytes. The composition of cytoplasmic granules includes peroxidase, histamine, inflammatory mediators, and other substances, the release of which at the site of activation causes the development of immediate allergic reactions: allergic rhinitis, some forms of asthma, anaphylactic shock. Like other white blood cells, basophils can leave the bloodstream, but their ability to amoeboid movement is limited. Lifespan is unknown.

Monocytes

Monocytes make up 2-9% of the total number of leukocytes. These are the largest leukocytes (diameter about 15 microns). Monocytes have a large bean-shaped nucleus, located eccentrically, in the cytoplasm there are typical organelles, phagocytic vacuoles, numerous lysosomes. Various substances formed in the foci of inflammation and tissue destruction are agents of chemotaxis and activation of monocytes. Activated monocytes secrete a number of biologically active substances - interleukin-1, endogenous pyrogens, prostaglandins, etc. Leaving the bloodstream, monocytes turn into macrophages, actively absorb bacteria and other large particles.

Lymphocytes

Lymphocytes make up 20-45% of the total number of leukocytes. They are round in shape, contain a large nucleus and a small amount of cytoplasm. In the cytoplasm, there are few lysosomes, mitochondria, a minimum of the endoplasmic reticulum, and a lot of free ribosomes. There are 2 morphologically similar, but functionally different groups of lymphocytes: T-lymphocytes (80%), formed in the thymus (thymus), and B-lymphocytes (10%), formed in the lymphoid tissue. Lymphocyte cells form short processes (microvilli), more numerous in B-lymphocytes. Lymphocytes play a central role in all immune reactions of the body (formation of antibodies, destruction of tumor cells, etc.). Most blood lymphocytes are in a functionally and metabolically inactive state. In response to specific signals, lymphocytes exit the vessels into the connective tissue. The main function of lymphocytes is to recognize and destroy target cells (most often viruses in a viral infection). The lifespan of lymphocytes varies from a few days to ten or more years.

Anemia is a decrease in red blood cell mass. Since blood volume is usually maintained at a constant level, the degree of anemia can be determined either from the volume of red blood cells expressed as a percentage of the total blood volume (hematocrit [BG]) or from the hemoglobin content of the blood. Normally, these indicators are different in men and women, since androgens increase both the secretion of erythropoietin and the number of bone marrow progenitor cells. When diagnosing anemia, it is also necessary to take into account that at high altitudes above sea level, where the oxygen tension is lower than normal, the values ​​of red blood indicators increase.

In women, anemia is indicated by the content of hemoglobin in the blood (Hb) less than 120 g / l and hematocrit (Ht) below 36%. In men, the occurrence of anemia is ascertained with Hb< 140 г/л и Ht < 42 %. НЬ не всегда отражает число циркулирующих эритроцитов. После острой кровопотери НЬ может оставаться в нормальных пределах при дефиците циркулирующих эритроцитов, обусловленном снижением объема циркулирующей крови (ОЦК). При беременности НЬ снижен вследствие увеличения объема плазмы крови при нормальном числе эритроцитов, циркулирующих с кровью.

Clinical signs of hemic hypoxia associated with a drop in the oxygen capacity of the blood due to a decrease in the number of circulating erythrocytes occur when Hb is less than 70 g / l. Severe anemia is indicated by pallor of the skin and tachycardia as a mechanism for maintaining adequate oxygen transport with the blood through an increase in the minute volume of blood circulation, despite its low oxygen capacity.

The content of reticulocytes in the blood reflects the intensity of the formation of red blood cells, that is, it is a criterion for the reaction of the bone marrow to anemia. The content of reticulocytes is usually measured as a percentage of the total number of erythrocytes, which contains a unit volume of blood. The reticulocyte index (RI) is an indicator of the correspondence between the reaction of increasing the formation of new erythrocytes by the bone marrow and the severity of anemia:

RI \u003d 0.5 x (content of reticulocytes x Ht of the patient / normal Ht).

RI, exceeding the level of 2-3%, indicates an adequate response to the intensification of erythropoiesis in response to anemia. A smaller value indicates the inhibition of the formation of erythrocytes by the bone marrow as a cause of anemia. Determining the value of the average erythrocyte volume is used to attribute anemia in a patient to one of three sets: a) microcytic; b) normocytic; c) macrocytic. Normocytic anemia is characterized by a normal volume of erythrocytes, with microcytic anemia it is reduced, and with macrocytic anemia it is increased.

The normal range of fluctuations in the average erythrocyte volume is 80-98 µm3. Anemia at a certain and individual for each patient level of hemoglobin concentration in the blood through a decrease in its oxygen capacity causes hemic hypoxia. Hemic hypoxia serves as a stimulus for a number of protective reactions aimed at optimizing and increasing systemic oxygen transport (Scheme 1). If compensatory reactions in response to anemia fail, then through neurohumoral adrenergic stimulation of resistance vessels and precapillary sphincters, the minute volume of blood circulation (MCV) is redistributed, aimed at maintaining a normal level of oxygen delivery to the brain, heart and lungs. In this case, in particular, the volumetric velocity of blood flow in the kidneys decreases.

Diabetes mellitus is primarily characterized by hyperglycemia, that is, a pathologically high blood glucose level, and other metabolic disorders associated with pathologically low secretion of insulin, the concentration of a normal hormone in the circulating blood, or resulting from a lack or absence of a normal response of target cells to action. hormone insulin. As a pathological condition of the whole organism, diabetes mellitus is mainly composed of metabolic disorders, including those secondary to hyperglycemia, pathological changes in microvessels (causes of retino- and nephropathy), accelerated arterial atherosclerosis, as well as neuropathy at the level of peripheral somatic nerves, sympathetic and parasympathetic nerves. conductors and ganglia.

There are two types of diabetes. Type I diabetes affects 10% of patients with both type 1 and type 2 diabetes. Diabetes mellitus type 1 is called insulin dependent, not only because patients need parenteral administration of exogenous insulin to eliminate hyperglycemia. Such a need may also arise in the treatment of patients with non-insulin-dependent diabetes mellitus. The fact is that without periodic administration of insulin, patients with type 1 diabetes mellitus develop diabetic ketoacidosis.

If insulin-dependent diabetes mellitus occurs as a result of an almost complete absence of insulin secretion, then the cause of non-insulin-dependent diabetes mellitus is partially reduced insulin secretion and (or) insulin resistance, that is, the absence of a normal systemic response to the release of the hormone by the insulin-producing cells of the islets of Langerhans of the pancreas.

Prolonged and extreme in strength action of inevitable stimuli as stress stimuli (postoperative period under conditions of ineffective analgesia, condition due to severe wounds and injuries, persistent negative psycho-emotional stress caused by unemployment and poverty, etc.) causes prolonged and pathogenic activation of the sympathetic division of the autonomic nervous system and the neuroendocrine catabolic system. These shifts in regulation, through a neurogenic decrease in insulin secretion and a stable predominance at the systemic level of the effects of catabolic hormones of insulin antagonists, can transform type II diabetes mellitus into insulin-dependent, which serves as an indication for parenteral insulin administration.

Hypothyroidism is a pathological condition due to a low level of secretion of thyroid hormones and the associated insufficiency of the normal action of hormones on cells, tissues, organs and the body as a whole.

Since the manifestations of hypothyroidism are similar to many signs of other diseases, when examining patients, hypothyroidism often goes unnoticed.

Primary hypothyroidism occurs as a result of diseases of the thyroid gland itself. Primary hypothyroidism can be a complication of the treatment of patients with thyrotoxicosis with radioactive iodine, operations on the thyroid gland, the effect of ionizing radiation on the thyroid gland (radiation therapy for lymphogranulomatosis in the neck), and in some patients it is a side effect of iodine-containing drugs.

In a number of developed countries, the most common cause of hypothyroidism is chronic autoimmune lymphocytic thyroiditis (Hashimoto's disease), which occurs more frequently in women than in men. In Hashimoto's disease, a uniform enlargement of the thyroid gland is hardly noticeable, and autoantibodies to thyroglobulin autoantigens and the microsomal fraction of the gland circulate with the blood of patients.

Hashimoto's disease as the cause of primary hypothyroidism often develops simultaneously with an autoimmune lesion of the adrenal cortex, causing a lack of secretion and effects of its hormones (autoimmune polyglandular syndrome).

Secondary hypothyroidism is a consequence of impaired secretion of thyroid-stimulating hormone (TSH) by the adenohypophysis. Most often, in patients with insufficient secretion of TSH, causing hypothyroidism, develops as a result of surgical interventions on the pituitary gland or is the result of the occurrence of its tumors. Secondary hypothyroidism is often combined with insufficient secretion of other hormones of the adenohypophysis, adrenocorticotropic and others.

To determine the type of hypothyroidism (primary or secondary) allows the study of the content of TSH and thyroxine (T4) in the blood serum. The low concentration of T4 with an increase in serum TSH indicates that, in accordance with the principle of negative feedback regulation, a decrease in the formation and release of T4 serves as a stimulus for an increase in the secretion of TSH by the adenohypophysis. In this case, hypothyroidism is defined as primary. When the serum TSH concentration is reduced in hypothyroidism, or if, despite hypothyroidism, the TSH concentration is in the normal range, the decrease in thyroid function is secondary hypothyroidism.

With implicit subclinical hypothyroidism, that is, with minimal clinical manifestations or the absence of symptoms of thyroid insufficiency, the concentration of T4 may be within normal fluctuations. At the same time, the level of TSH in the serum is increased, which can presumably be associated with an increase in the secretion of TSH by the adenohypophysis in response to the action of thyroid hormones that is inadequate to the needs of the body. In such patients, in pathogenetic terms, it may be justified to prescribe thyroid preparations to restore the normal intensity of the action of thyroid hormones at the systemic level (replacement therapy).

More rare causes of hypothyroidism are genetically determined hypoplasia of the thyroid gland (congenital athyreosis), hereditary disorders in the synthesis of its hormones associated with the absence of normal gene expression of certain enzymes or its deficiency, congenital or acquired reduced sensitivity of cells and tissues to the action of hormones, as well as low intake iodine as a substrate for the synthesis of thyroid hormones from the external environment to the internal.

Hypothyroidism can be considered a pathological condition caused by a deficiency in the circulating blood and the whole body of free thyroid hormones. It is known that the thyroid hormones triiodothyronine (Tz) and thyroxine bind to the nuclear receptors of target cells. The affinity of thyroid hormones for nuclear receptors is high. At the same time, the affinity for Tz is ten times higher than the affinity for T4.

The main effect of thyroid hormones on metabolism is an increase in oxygen consumption and the capture of free energy by cells as a result of increased biological oxidation. Therefore, oxygen consumption in conditions of relative rest in patients with hypothyroidism is at a pathologically low level. This effect of hypothyroidism is observed in all cells, tissues and organs, except for the brain, cells of the mononuclear phagocyte system and gonads.

Thus, evolution has partially preserved energy metabolism at the suprasegmental level of systemic regulation, in a key link in the immune system, and also the provision of free energy for reproductive function, independent of possible hypothyroidism. However, a mass deficiency in the effectors of the endocrine metabolic regulation system (deficiency of thyroid hormones) leads to a deficiency of free energy (hypoergosis) at the systemic level. We consider this to be one of the manifestations of the action of the general regularity of the development of the disease and the pathological process due to dysregulation - through the deficit of mass and energy in the regulatory systems to the deficit of mass and energy at the level of the whole organism.

Systemic hypoergosis and a drop in the excitability of nerve centers due to hypothyroidism manifests itself as such characteristic symptoms of insufficient thyroid function as increased fatigue, drowsiness, as well as slowing down of speech and a drop in cognitive functions. Violations of intracentral relations due to hypothyroidism are the result of slow mental development of patients with hypothyroidism, as well as a decrease in the intensity of nonspecific afferentation due to systemic hypoergosis.

Most of the free energy utilized by the cell is used to operate the Na+/K+-ATPase pump. Thyroid hormones increase the efficiency of this pump by increasing the number of its constituent elements. Since almost all cells have such a pump and respond to thyroid hormones, the systemic effects of thyroid hormones include an increase in the efficiency of this mechanism of active transmembrane ion transport. This occurs through increased cellular uptake of free energy and through an increase in the number of units of the Na+/K+-ATPase pump.

Thyroid hormones increase the sensitivity of adrenoreceptors of the heart, blood vessels and other function effectors. At the same time, in comparison with other regulatory influences, adrenergic stimulation increases to the greatest extent, since at the same time hormones suppress the activity of the enzyme monoamine oxidase, which destroys the sympathetic mediator norepinephrine. Hypothyroidism, reducing the intensity of adrenergic stimulation of effectors of the circulatory system, leads to a decrease in cardiac output (MOV) and bradycardia in conditions of relative rest. Another reason for the low values ​​of minute volume of blood circulation is a reduced level of oxygen consumption as a determinant of the IOC. The decrease in adrenergic stimulation of the sweat glands manifests itself as a characteristic dryness of the rut.

Hypothyroid (myxematous) coma is a rare complication of hypothyroidism, which mainly consists of the following dysfunctions and homeostasis disorders:

¦ Hypoventilation as a result of a drop in the formation of carbon dioxide, which is exacerbated by central hypopnea due to hypoergosis of the neurons of the respiratory center. Therefore, hypoventilation in myxematous coma may be the cause of arterial hypoxemia.

¦ Arterial hypotension as a result of a decrease in the IOC and hypoergosis of neurons of the vasomotor center, as well as a decrease in the sensitivity of adrenergic receptors of the heart and vascular wall.

¦ Hypothermia as a result of a decrease in the intensity of biological oxidation at the system level.

Constipation as a characteristic symptom of hypothyroidism is probably due to systemic hypoergosis and may be the result of disorders of intracentral relations due to a decrease in thyroid function.

Thyroid hormones, like corticosteroids, induce protein synthesis by activating the mechanism of gene transcription. This is the main mechanism by which the effect of Tz on cells enhances overall protein synthesis and ensures a positive nitrogen balance. Therefore, hypothyroidism often causes a negative nitrogen balance.

Thyroid hormones and glucocorticoids increase the level of transcription of the human growth hormone (somatotropin) gene. Therefore, the development of hypothyroidism in childhood can be the cause of body growth retardation. Thyroid hormones stimulate protein synthesis at the systemic level not only through increased expression of the somatotropin gene. They enhance protein synthesis by modulating the functioning of other elements of the genetic material of cells and increasing the permeability of the plasma membrane for amino acids. In this regard, hypothyroidism can be considered a pathological condition that characterizes the inhibition of protein synthesis as the cause of mental retardation and body growth in children with hypothyroidism. The impossibility of rapid intensification of protein synthesis in immunocompetent cells associated with hypothyroidism can cause dysregulation of a specific immune response and acquired immunodeficiency due to dysfunctions of both T- and B-cells.

One of the effects of thyroid hormones on metabolism is an increase in lipolysis and fatty acid oxidation with a decrease in their level in the circulating blood. The low intensity of lipolysis in patients with hypothyroidism leads to the accumulation of fat in the body, which causes a pathological increase in body weight. The increase in body weight is often moderate, which is associated with anorexia (the result of a decrease in the excitability of the nervous system and the expenditure of free energy by the body) and a low level of protein synthesis in patients with hypothyroidism.

Thyroid hormones are important effectors of developmental regulation systems in the course of ontogenesis. Therefore, hypothyroidism in fetuses or newborns leads to cretinism (fr. cretin, stupid), that is, a combination of multiple developmental defects and an irreversible delay in the normal development of mental and cognitive functions. For most patients with cretinism due to hypothyroidism, myxedema is characteristic.

The pathological state of the body due to pathogenically excessive secretion of thyroid hormones is called hyperthyroidism. Thyrotoxicosis is understood as hyperthyroidism of extreme severity.

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Definition of the concept of the blood system

Blood system(according to G.F. Lang, 1939) - a combination of blood itself, hematopoietic organs, blood destruction (red bone marrow, thymus, spleen, lymph nodes) and neurohumoral regulatory mechanisms, due to which the constancy of the composition and function of the blood is preserved.

Currently, the blood system is functionally supplemented with organs for the synthesis of plasma proteins (liver), delivery to the bloodstream and excretion of water and electrolytes (intestines, nights). The most important features of blood as a functional system are the following:

• it can perform its functions only in a liquid state of aggregation and in constant motion (through the blood vessels and cavities of the heart);
• all its constituent parts are formed outside the vascular bed;
• it combines the work of many physiological systems of the body.

The composition and amount of blood in the body

Blood is a liquid connective tissue, which consists of a liquid part - and cells suspended in it - : (red blood cells), (white blood cells), (platelets). In an adult, blood cells make up about 40-48%, and plasma - 52-60%. This ratio is called hematocrit (from the Greek. haima- blood, kritos- index). The composition of the blood is shown in Fig. one.

Rice. 1. Composition of the blood

The total amount of blood (how much blood) in the body of an adult is normally 6-8% of body weight, i.e. about 5-6 liters.

Physico-chemical properties of blood and plasma

How much blood is in the human body?

The share of blood in an adult accounts for 6-8% of body weight, which corresponds to approximately 4.5-6.0 liters (with an average weight of 70 kg). In children and athletes, the blood volume is 1.5-2.0 times greater. In newborns, it is 15% of body weight, in children of the 1st year of life - 11%. In humans, under conditions of physiological rest, not all blood actively circulates through the cardiovascular system. Part of it is in the blood depots - venules and veins of the liver, spleen, lungs, skin, in which the blood flow rate is significantly reduced. The total amount of blood in the body remains relatively constant. A rapid loss of 30-50% of the blood can lead the body to death. In these cases, an urgent transfusion of blood products or blood-substituting solutions is necessary.

Blood viscosity due to the presence in it of uniform elements, primarily erythrocytes, proteins and lipoproteins. If the viscosity of water is taken as 1, then the viscosity of whole blood of a healthy person will be about 4.5 (3.5-5.4), and plasma - about 2.2 (1.9-2.6). The relative density (specific gravity) of blood depends mainly on the number of erythrocytes and the content of proteins in the plasma. In a healthy adult, the relative density of whole blood is 1.050-1.060 kg/l, erythrocyte mass - 1.080-1.090 kg/l, blood plasma - 1.029-1.034 kg/l. In men, it is somewhat larger than in women. The highest relative density of whole blood (1.060-1.080 kg/l) is observed in newborns. These differences are explained by the difference in the number of red blood cells in the blood of people of different sex and age.

Hematocrit- part of the blood volume attributable to the proportion of formed elements (primarily erythrocytes). Normally, the hematocrit of the circulating blood of an adult is on average 40-45% (for men - 40-49%, for women - 36-42%). In newborns, it is about 10% higher, and in young children it is about the same amount lower than in an adult.

Blood plasma: composition and properties

The osmotic pressure of blood, lymph and tissue fluid determines the exchange of water between blood and tissues. A change in the osmotic pressure of the fluid surrounding the cells leads to a violation of their water metabolism. This can be seen in the example of erythrocytes, which in a hypertonic solution of NaCl (a lot of salt) lose water and shrivel. In a hypotonic solution of NaCl (little salt), erythrocytes, on the contrary, swell, increase in volume and may burst.

The osmotic pressure of blood depends on the salts dissolved in it. About 60% of this pressure is created by NaCl. The osmotic pressure of blood, lymph and tissue fluid is approximately the same (approximately 290-300 mosm / l, or 7.6 atm) and is constant. Even in cases where a significant amount of water or salt enters the blood, the osmotic pressure does not undergo significant changes. With excessive intake of water into the blood, water is quickly excreted by the kidneys and passes into the tissues, which restores the initial value of the osmotic pressure. If the concentration of salts in the blood rises, then water from the tissue fluid passes into the vascular bed, and the kidneys begin to excrete salt intensively. Digestion products of proteins, fats and carbohydrates, absorbed into the blood and lymph, as well as low molecular weight products of cellular metabolism, can change the osmotic pressure within a small range.

Maintaining a constant osmotic pressure plays a very important role in the life of cells.

Hydrogen ion concentration and blood pH regulation

The blood has a slightly alkaline environment: the pH of the arterial blood is 7.4; The pH of venous blood due to the high content of carbon dioxide in it is 7.35. Inside the cells, the pH is somewhat lower (7.0-7.2), which is due to the formation of acidic products in them during metabolism. The extreme limits of pH changes compatible with life are values ​​from 7.2 to 7.6. A shift in pH beyond these limits causes severe impairment and can lead to death. In healthy people, it ranges from 7.35-7.40. A prolonged shift in pH in humans, even by 0.1-0.2, can be fatal.

So, at pH 6.95, loss of consciousness occurs, and if these shifts are not eliminated in the shortest possible time, then a fatal outcome is inevitable. If the pH becomes equal to 7.7, then severe convulsions (tetany) occur, which can also lead to death.

In the process of metabolism, tissues secrete “acidic” metabolic products into the tissue fluid, and, consequently, into the blood, which should lead to a shift in pH to the acid side. So, as a result of intense muscular activity, up to 90 g of lactic acid can enter the human blood within a few minutes. If this amount of lactic acid is added to a volume of distilled water equal to the volume of circulating blood, then the concentration of ions in it will increase by 40,000 times. The reaction of the blood under these conditions practically does not change, which is explained by the presence of buffer systems in the blood. In addition, the pH in the body is maintained due to the work of the kidneys and lungs, which remove carbon dioxide, excess salts, acids and alkalis from the blood.

The constancy of blood pH is maintained buffer systems: hemoglobin, carbonate, phosphate and plasma proteins.

Hemoglobin buffer system the most powerful. It accounts for 75% of the buffer capacity of the blood. This system consists of reduced hemoglobin (HHb) and its potassium salt (KHb). Its buffering properties are due to the fact that, with an excess of H + KHb, it gives up K + ions, and itself adds H + and becomes a very weakly dissociating acid. In tissues, the blood hemoglobin system performs the function of an alkali, preventing acidification of the blood due to the ingress of carbon dioxide and H + ions into it. In the lungs, hemoglobin behaves like an acid, preventing the blood from becoming alkaline after carbon dioxide is released from it.

Carbonate buffer system(H 2 CO 3 and NaHC0 3) in its power takes the second place after the hemoglobin system. It functions as follows: NaHCO 3 dissociates into Na + and HC0 3 - ions. When a stronger acid than carbonic enters the blood, an exchange reaction of Na + ions occurs with the formation of weakly dissociating and easily soluble H 2 CO 3. Thus, an increase in the concentration of H + ions in the blood is prevented. An increase in the content of carbonic acid in the blood leads to its breakdown (under the influence of a special enzyme found in erythrocytes - carbonic anhydrase) into water and carbon dioxide. The latter enters the lungs and is released into the environment. As a result of these processes, the entry of acid into the blood leads to only a slight temporary increase in the content of neutral salt without a shift in pH. In the case of alkali entering the blood, it reacts with carbonic acid, forming bicarbonate (NaHC0 3) and water. The resulting deficiency of carbonic acid is immediately compensated by a decrease in the release of carbon dioxide by the lungs.

Phosphate buffer system formed by sodium dihydrophosphate (NaH 2 P0 4) and sodium hydrogen phosphate (Na 2 HP0 4). The first compound dissociates weakly and behaves like a weak acid. The second compound has alkaline properties. When a stronger acid is introduced into the blood, it reacts with Na,HP0 4 , forming a neutral salt and increasing the amount of slightly dissociating sodium dihydrogen phosphate. If a strong alkali is introduced into the blood, it interacts with sodium dihydrogen phosphate, forming weakly alkaline sodium hydrogen phosphate; The pH of the blood at the same time changes slightly. In both cases, excess sodium dihydrophosphate and sodium hydrogen phosphate are excreted in the urine.

Plasma proteins play the role of a buffer system due to their amphoteric properties. In an acidic environment, they behave like alkalis, binding acids. In an alkaline environment, proteins react as acids that bind alkalis.

Nervous regulation plays an important role in maintaining blood pH. In this case, the chemoreceptors of the vascular reflexogenic zones are predominantly irritated, the impulses from which enter the medulla oblongata and other parts of the central nervous system, which reflexively includes peripheral organs in the reaction - the kidneys, lungs, sweat glands, gastrointestinal tract, whose activity is aimed at restoring the initial pH values. So, when the pH shifts to the acid side, the kidneys intensively excrete the anion H 2 P0 4 - with urine. When the pH shifts to the alkaline side, the excretion of anions HP0 4 -2 and HC0 3 - by the kidneys increases. The human sweat glands are able to remove excess lactic acid, and the lungs - CO2.

Under various pathological conditions, a pH shift can be observed both in an acidic and in an alkaline environment. The first of these is called acidosis, second - alkalosis.

The ancients said that the secret is hidden in the water. Is it so? Let's think. The two most important fluids in the human body are blood and lymph. The composition and functions of the first, we will consider in detail today. People always remember about diseases, their symptoms, the importance of maintaining a healthy lifestyle, but they forget that blood has a huge impact on health. Let's talk in detail about the composition, properties and functions of blood.

Introduction to the topic

To begin with, it is worth deciding what blood is. Generally speaking, this is a special type of connective tissue, which in its essence is a liquid intercellular substance that circulates through the blood vessels, bringing useful substances to each cell of the body. Without blood, a person dies. There are a number of diseases, which we will discuss below, that spoil the properties of the blood, leading to negative or even fatal consequences.

The body of an adult contains approximately four to five liters of blood. It is also believed that the red liquid makes up a third of a person's weight. 60% is plasma and 40% is formed elements.

Compound

The composition of the blood and the functions of the blood are numerous. Let's start with the composition. Plasma and formed elements are the main components.

The formed elements, which will be discussed in detail below, consist of erythrocytes, platelets and leukocytes. What does plasma look like? It resembles an almost transparent liquid with a yellowish tint. Almost 90% of plasma consists of water, but it also contains mineral and organic substances, proteins, fats, glucose, hormones, amino acids, vitamins and a variety of products of the metabolic process.

Blood plasma, the composition and functions of which we are considering, is the necessary environment in which the formed elements exist. Plasma is made up of three main proteins - globulins, albumins and fibrinogen. Interestingly, it even contains gases in a small amount.

red blood cells

The composition of the blood and the functions of the blood cannot be considered without a detailed study of erythrocytes - red cells. Under a microscope, they were found to resemble concave discs in appearance. They do not have nuclei. The cytoplasm contains the protein hemoglobin, which is important for human health. If it is not enough, the person falls ill with anemia. Since hemoglobin is a complex substance, it consists of heme pigment and globin protein. Iron is an important structural element.

Erythrocytes perform the most important function - they carry oxygen and carbon dioxide through the vessels. It is they that nourish the body, help it live and develop, because without air a person dies in a few minutes, and the brain, with insufficient work of red blood cells, can experience oxygen starvation. Although the red cells themselves do not have a nucleus, they still develop from nuclear cells. The latter mature in the red bone marrow. As they mature, red cells lose their nucleus and become shaped elements. Interestingly, the life cycle of red blood cells is about 130 days. After that, they are destroyed in the spleen or liver. Bile pigment is formed from hemoglobin protein.

platelets

Platelets have neither color nor nucleus. These are cells of a rounded shape, which outwardly resemble plates. Their main task is to ensure sufficient blood clotting. One liter of human blood can contain from 200 to 400 thousand of these cells. The site of platelet formation is the red bone marrow. Cells are destroyed in case of even the slightest damage to blood vessels.

Leukocytes

Leukocytes also perform important functions, which will be discussed below. First, let's talk about their appearance. Leukocytes are white bodies that do not have a fixed shape. The formation of cells occurs in the spleen, lymph nodes and bone marrow. By the way, leukocytes have nuclei. Their life cycle is much shorter than that of red blood cells. They exist for an average of three days, after which they are destroyed in the spleen.

Leukocytes perform a very important function - they protect a person from a variety of bacteria, foreign proteins, etc. Leukocytes can penetrate through thin capillary walls, analyzing the environment in the intercellular space. The fact is that these small bodies are extremely sensitive to various chemical secretions that are formed during the decay of bacteria.

Speaking figuratively and clearly, one can imagine the work of leukocytes as follows: getting into the intercellular space, they analyze the environment and look for bacteria or decay products. Having found a negative factor, leukocytes approach it and absorb it into themselves, that is, they absorb it, then inside the body the harmful substance is split with the help of secreted enzymes.

It will be useful to know that these white blood cells have intracellular digestion. At the same time, protecting the body from harmful bacteria, a large number of leukocytes die. Thus, the bacterium is not destroyed and decay products and pus accumulate around it. Over time, new white blood cells absorb it all and digest it. It is interesting that I. Mechnikov was very carried away by this phenomenon, who called the white shaped elements phagocytes, and gave the name phagocytosis to the very process of absorption of harmful bacteria. In a broader sense, this word will be used in the sense of the general defensive reaction of the body.

blood properties

Blood has certain properties. There are three main ones:

1. Colloidal, which directly depend on the amount of protein in the plasma. It is known that protein molecules can retain water, therefore, thanks to this property, the liquid composition of the blood is stable.
2. Suspension: also associated with the presence of protein and the ratio of albumin and globulins.
3. Electrolyte: affect osmotic pressure. Depend on the ratio of anions and cations.

Functions

The work of the human circulatory system is not interrupted even for a minute. In every second of time, blood performs a number of important functions for the body. Which ones? Experts identify four main functions:

1. Protective. It is clear that one of the main functions is to protect the body. This happens at the level of cells that repel or destroy foreign or harmful bacteria.
2. Homeostatic. The body works properly only in a stable environment, so consistency plays a huge role. Maintaining homeostasis (balance) means controlling the water-electrolyte balance, acid-base balance, etc.
3. Mechanical is an important function that ensures the health of organs. It consists in the turgor tension that the organs experience during a rush of blood.
4. Transport is another function, which lies in the fact that the body receives everything it needs through the blood. All useful substances that come with food, water, vitamins, injections, etc. do not directly diverge to the organs, but through the blood, which nourishes all body systems equally.

The last function has several sub-functions that are worth considering separately.

Respiratory is that oxygen is transferred from the lungs to the tissues, and carbon dioxide from the tissues to the lungs.

Nutritional subfunction refers to the delivery of nutrients to the tissues.

The excretory subfunction is to transport waste products to the liver and lungs for their further excretion from the body.

No less important is thermoregulation, on which body temperature depends. The regulatory subfunction is to transport hormones - signaling substances that are necessary for all body systems.

The composition of the blood and the functions of the formed elements of the blood determine the health of a person and his well-being. Deficiency or excess of certain substances can lead to mild ailments such as dizziness or to serious illnesses. Blood performs its functions clearly, the main thing is that the products of transportation are useful for the body.

Blood types

The composition, properties and functions of blood, we examined in detail above. Now it's time to talk about blood types. Belonging to a particular group is determined by a set of specific antigenic properties of red blood cells. Each person has a certain blood type, which does not change throughout life and is innate. The most important grouping is the division into four groups according to the "AB0" system and into two groups according to the Rh factor.

In the modern world, blood transfusion is very often required, which we will discuss below. So, for the success of this process, the blood of the donor and the recipient must match. However, not everything is decided by compatibility, there are interesting exceptions. People with blood type I can be universal donors for people with any blood type. Those with IV blood group are universal recipients.

It is quite possible to predict the blood type of the future baby. To do this, you need to know the blood group of the parents. A detailed analysis will make it possible to guess the future blood type with a high probability.

Blood transfusion

A blood transfusion may be required for a number of diseases or for large blood loss in case of severe injury. Blood, the structure, composition and functions of which we have examined, is not a universal liquid, therefore it is important to timely transfuse the nominal group that the patient needs. With a large blood loss, internal blood pressure drops and the amount of hemoglobin decreases, and the internal environment ceases to be stable, that is, the body cannot function normally.

The approximate composition of blood and the functions of blood elements were known in antiquity. Then the doctors were also involved in transfusion, which often saved the life of the patient, but the mortality rate from this method of treatment was incredibly high due to the fact that there was no concept of compatibility of blood groups at that time. However, death could occur not only as a result of this. Sometimes death occurred due to the fact that donor cells stuck together and formed lumps that clogged blood vessels and disrupted blood circulation. This effect of transfusion is called agglutination.

Blood diseases

The composition of the blood, its main functions affect the overall well-being and health. If there are any violations, various diseases can occur. Hematology deals with the study of the clinical picture of diseases, their diagnosis, treatment, pathogenesis, prognosis and prevention. However, blood diseases can also be malignant. Oncohematology is engaged in their study.

One of the most common diseases is anemia, in which case it is necessary to saturate the blood with iron-containing products. Its composition, quantity and functions are affected by this disease. By the way, if the disease is started, you can end up in the hospital. The concept of "anemia" includes a number of clinical syndromes that are associated with a single symptom - a decrease in the amount of hemoglobin in the blood. Very often this occurs against the background of a decrease in the number of red blood cells, but not always. Anemia should not be understood as one disease. Often it is just a symptom of another disease.

Hemolytic anemia is a blood disease in which the body is massive destruction of red blood cells. Hemolytic disease in newborns occurs when there is an incompatibility between mother and child in terms of blood type or Rh factor. In this case, the mother's body perceives the formed elements of the child's blood as foreign agents. For this reason, children most often suffer from jaundice.

Hemophilia is a disease that is manifested by poor blood clotting, which, with minor tissue damage without immediate intervention, can lead to death. The composition of the blood and the functions of the blood may not be the cause of the disease, sometimes it lies in the blood vessels. For example, in hemorrhagic vasculitis, the walls of microvessels are damaged, which causes the formation of microthrombi. This process affects the kidneys and intestines most of all.

animal blood

The composition of the blood and the functions of the blood in animals have their own differences. In invertebrates, the proportion of blood in the total body weight is approximately 20-30%. It is interesting that in vertebrates the same figure reaches only 2-8%. In the world of animals, blood is more diverse than in humans. Separately, it is worth talking about the composition of the blood. The functions of blood are similar, but the composition can be completely different. There is iron-containing blood that flows in the veins of vertebrates. It is red in color, similar to human blood. Iron-containing blood based on hemerythrin is characteristic of worms. Spiders and various cephalopods are naturally rewarded with blood based on hemocyanin, that is, their blood contains not iron, but copper.

Animal blood is used in different ways. National dishes are prepared from it, albumin and medicines are created. However, in many religions it is forbidden to eat the blood of any animal. Because of this, there are certain techniques for slaughtering and preparing animal food.

As we have already understood, the most important role in the body is assigned to the blood system. Its composition and functions determine the health of every organ, brain and all other body systems. What should be done to be healthy? It's very simple: think about what substances your blood carries through the body every day. Is it the right healthy food, in which the rules of preparation, proportions, etc. are observed, or is it processed food, food from fast food stores, tasty, but unhealthy food? Pay special attention to the quality of the water you drink. The composition of blood and the functions of blood largely depend on its composition. What is the fact that the plasma itself is 90% water. Blood (composition, functions, metabolism - in the article above) is the most important fluid for the body, remember this.