What is contained in the blood. General properties and functions of blood

The normal functioning of the body's cells is possible only if its internal environment is constant. The true internal environment of the body is the intercellular (interstitial) fluid, which is in direct contact with the cells. However, the constancy of the intercellular fluid is largely determined by the composition of the blood and lymph, therefore, in a broad sense of the internal environment, its composition includes: intercellular fluid, blood and lymph, cerebrospinal, joint and pleural fluid. There is a constant exchange between the intercellular fluid and lymph, aimed at ensuring a continuous supply of necessary substances to the cells and removing their waste products from there.

The constancy of the chemical composition and physicochemical properties of the internal environment is called homeostasis.

Homeostasis- this is the dynamic constancy of the internal environment, which is characterized by many relatively constant quantitative indicators, called physiological, or biological, constants. These constants provide optimal (best) conditions for the life of the body’s cells, and on the other hand, reflect its normal state.

The most important component of the internal environment of the body is blood. Lang's concept of the blood system includes blood, the moral apparatus regulating the neuron, as well as the organs in which the formation and destruction of blood cells occurs (bone marrow, lymph nodes, thymus, spleen and liver).

Blood functions

Blood performs the following functions.

Transport function - is the transport by blood of various substances (energy and information contained in them) and heat within the body.

Respiratory function - blood carries respiratory gases - oxygen (0 2) and carbon dioxide (CO?) - both in physically dissolved and chemically bound form. Oxygen is delivered from the lungs to the cells of organs and tissues that consume it, and carbon dioxide, on the contrary, from the cells to the lungs.

Nutritious function - the blood also transports blinking substances from the organs where they are absorbed or deposited to the place of their consumption.

Excretory (excretory) function - during the biological oxidation of nutrients, in cells, in addition to CO 2, other metabolic end products (urea, uric acid) are formed, which are transported by the blood to the excretory organs: kidneys, lungs, sweat glands, intestines. Blood also transports hormones, other signaling molecules and biologically active substances.

Thermostatic function - due to its high heat capacity, blood ensures the transfer of heat and its redistribution in the body. The blood transfers about 70% of the heat generated in the internal organs to the skin and lungs, which ensures that they dissipate heat into the environment.

Homeostatic function - blood participates in water-salt metabolism in the body and ensures the maintenance of the constancy of its internal environment - homeostasis.

Protective the function is primarily to ensure immune reactions, as well as create blood and tissue barriers against foreign substances, microorganisms, and defective cells of one’s own body. The second manifestation of the protective function of blood is its participation in maintaining its liquid state of aggregation (fluidity), as well as stopping bleeding when the walls of blood vessels are damaged and restoring their patency after repair of defects.

Blood system and its functions

The idea of ​​blood as a system was created by our compatriot G.F. Lang in 1939. He included four parts to this system:

• peripheral blood circulating through the vessels;
• hematopoietic organs (red bone marrow, lymph nodes and spleen);
• organs of blood destruction;
• regulating neurohumoral apparatus.

The blood system is one of the life support systems of the body and performs many functions:

• transport - circulating through the vessels, blood performs a transport function that determines a number of others;
• respiratory— binding and transfer of oxygen and carbon dioxide;
• trophic (nutritional) - blood provides all cells of the body with nutrients: glucose, amino acids, fats, minerals, water;
• excretory (excretory) - blood carries away “waste” from the tissues - the end products of metabolism: urea, uric acid and other substances removed from the body by the excretory organs;
• thermoregulatory- blood cools energy-consuming organs and warms organs that lose heat. The body has mechanisms that ensure rapid constriction of skin blood vessels when the ambient temperature drops and dilation of blood vessels when it rises. This leads to a decrease or increase in heat loss, since the plasma consists of 90-92% water and, as a result, has high thermal conductivity and specific heat capacity;
• homeostatic - blood maintains the stability of a number of homeostasis constants - osmotic pressure, etc.;
• security water-salt metabolism between blood and tissues - in the arterial part of the capillaries, liquid and salts enter the tissues, and in the venous part of the capillaries they return to the blood;
• protective - blood is the most important factor of immunity, i.e. protecting the body from living bodies and genetically foreign substances. This is determined by the phagocytic activity of leukocytes (cellular immunity) and the presence of antibodies in the blood that neutralize microbes and their poisons (humoral immunity);
• humoral regulation - Due to its transport function, blood ensures chemical interaction between all parts of the body, i.e. humoral regulation. Blood carries hormones and other biologically active substances from the cells where they are formed to other cells;
• implementation of creative connections. Macromolecules carried by plasma and blood cells carry out intercellular information transfer, ensuring the regulation of intracellular processes of protein synthesis, maintaining the degree of cell differentiation, restoration and maintenance of tissue structure.

Blood functions.

Blood is a liquid tissue consisting of plasma and blood cells suspended in it. Blood circulation through a closed cardiovascular system is a necessary condition for maintaining the constancy of its composition. Stopping the heart and stopping blood flow immediately leads the body to death. The study of blood and its diseases is called hematology.

Physiological functions of blood:

1. Respiratory - transfer of oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs.

2. Trophic (nutritional) – delivers nutrients, vitamins, mineral salts, water from the digestive organs to the tissues.

3. Excretory (excretory) – release from tissues of final decay products, excess water and mineral salts.

4. Thermoregulatory – regulation of body temperature by cooling energy-intensive organs and warming organs that lose heat.

5. Homeostatic – maintaining the stability of a number of homeostasis constants (ph, osmotic pressure, isoionicity).

6. Regulation of water-salt exchange between blood and tissues.

7. Protective – participation in cellular (leukocytes) and humoral (At) immunity, in the process of coagulation to stop bleeding.

8. Humoral – transfer of hormones.

9. Creative (creative) – transfer of macromolecules that carry out intercellular information transfer in order to restore and maintain the structure of body tissues.

Quantity and physicochemical properties of blood.

The total amount of blood in the body of an adult is normally 6-8% of body weight and is approximately 4.5-6 liters. Blood consists of a liquid part - plasma and blood cells suspended in it - formed elements: red (erythrocytes), white (leukocytes) and blood platelets (platelets). In circulating blood, formed elements make up 40-45%, plasma accounts for 55-60%. In deposited blood, on the contrary: formed elements - 55-60%, plasma - 40-45%.

The viscosity of whole blood is about 5, and the viscosity of plasma is 1.7–2.2 (relative to the viscosity of water of 1). The viscosity of blood is due to the presence of proteins and especially red blood cells.

Osmotic pressure is the pressure exerted by substances dissolved in the plasma. It depends mainly on the mineral salts it contains and averages 7.6 atm, which corresponds to the freezing point of blood equal to -0.56 - -0.58 ° C. About 60% of the total osmotic pressure is due to Na salts.

Blood oncotic pressure is the pressure created by plasma proteins (i.e. their ability to attract and retain water). Determined by more than 80% albumin.

The blood reaction is determined by the concentration of hydrogen ions, which is expressed as a hydrogen indicator - pH.

In a neutral environment pH = 7.0

In acidic - less than 7.0.

In alkaline – more than 7.0.

Blood has a pH of 7.36, i.e. its reaction is slightly alkaline. Life is possible within a narrow range of pH shifts from 7.0 to 7.8 (since only under these conditions can enzymes - catalysts of all biochemical reactions - work).

Blood plasma.

Blood plasma is a complex mixture of proteins, amino acids, carbohydrates, fats, salts, hormones, enzymes, antibodies, dissolved gases and protein breakdown products (urea, uric acid, creatinine, ammonia) that must be excreted from the body. Plasma contains 90-92% water and 8-10% dry matter, mainly proteins and mineral salts. Plasma has a slightly alkaline reaction (pH = 7.36).

Plasma proteins (there are more than 30 of them) include 3 main groups:

· Globulins ensure the transport of fats, lipoids, glucose, copper, iron, the production of antibodies, as well as α- and β-agglutinins in the blood.

· Albumins provide oncotic pressure, bind drugs, vitamins, hormones, and pigments.

· Fibrinogen is involved in blood clotting.

Formed elements of blood.

Red blood cells (from the Greek erytros - red, cytus - cell) are nuclear-free blood cells containing hemoglobin. They have the shape of biconcave disks with a diameter of 7-8 microns and a thickness of 2 microns. They are very flexible and elastic, easily deformed and pass through blood capillaries with a diameter smaller than the diameter of a red blood cell. The lifespan of red blood cells is 100-120 days.

In the initial phases of their development, red blood cells have a nucleus and are called reticulocytes. As it matures, the nucleus is replaced by respiratory pigment - hemoglobin, which makes up 90% of the dry matter of erythrocytes.

Normally, 1 μl (1 cubic mm) of blood in men contains 4-5 million red blood cells, in women – 3.7-4.7 million, in newborns the number of red blood cells reaches 6 million. Increase in the number of red blood cells per unit volume of blood is called erythrocytosis, a decrease is called erythropenia. Hemoglobin is the main component of red blood cells, ensures the respiratory function of the blood through the transport of oxygen and carbon dioxide and regulates the pH of the blood, having the properties of weak acids.

Normally, men contain 145 g/l of hemoglobin (with fluctuations 130-160 g/l), women – 130 g/l (120-140 g/l). The total amount of hemoglobin in five liters of blood in a person is 700-800 g.

Leukocytes (from the Greek leukos - white, cytus - cell) are colorless nuclear cells. The size of leukocytes is 8-20 microns. They are formed in the red bone marrow, lymph nodes, and spleen. 1 μl of human blood normally contains 4-9 thousand leukocytes. Their number fluctuates throughout the day, is reduced in the morning, increases after eating (digestive leukocytosis), increases during muscular work, and strong emotions.

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

The lifespan of leukocytes is on average 15-20 days, lymphocytes - 20 years or more. Some lymphocytes live throughout a person's life.

Based on the presence of granularity in the cytoplasm, leukocytes are divided into 2 groups: granular (granulocytes) and non-granular (agranulocytes).

The group of granulocytes includes neutrophils, eosinophils and basophils. They have a large number of granules in the cytoplasm, which contain enzymes necessary for the digestion of foreign substances. The nuclei of all granulocytes are divided into 2–5 parts, interconnected by threads, which is why they are also called segmented leukocytes. Young forms of neutrophils with nuclei in the form of rods are called band neutrophils, and those in the form of an oval are called young.

Lymphocytes are the smallest of the leukocytes and have a large round nucleus surrounded by a narrow rim of cytoplasm.

Monocytes are large agranulocytes with an oval or bean-shaped nucleus.

The percentage of individual types of leukocytes in the blood is called the leukocyte formula, or leukogram:

· eosinophils 1 – 4%

· basophils 0.5%

· neutrophils 60 – 70%

lymphocytes 25 – 30%

· monocytes 6 – 8%

In healthy people, the leukogram is quite constant, and its changes are a sign of various diseases. For example, in acute inflammatory processes there is an increase in the number of neutrophils (neutrophilia), in allergic diseases and helminthic disease - an increase in the number of eosinophils (eosinophilia), in sluggish chronic infections (tuberculosis, rheumatism, etc.) - the number of lymphocytes (lymphocytosis).

Neutrophils can be used to determine a person's sex. In the presence of a female genotype, 7 out of 500 neutrophils contain special, female-specific formations called “drumsticks” (round outgrowths with a diameter of 1.5-2 μm, connected to one of the segments of the nucleus through thin chromatin bridges).

Leukocytes perform many functions:

1. Protective – fight against foreign agents (they phagocytose (absorb) foreign bodies and destroy them).

2. Antitoxic – production of antitoxins that neutralize the waste products of microbes.

3. Production of antibodies that provide immunity, i.e. immunity to infections and genetically foreign substances.

4. Participate in the development of all stages of inflammation, stimulate recovery (regenerative) processes in the body and accelerate wound healing.

5. Provide graft rejection and destruction of own mutant cells.

6. They form active (endogenous) pyrogens and form a febrile reaction.

Platelets, or blood platelets (Greek thrombos - blood clot, cytus - cell) are round or oval non-nuclear formations with a diameter of 2-5 microns (3 times smaller than red blood cells). Platelets are formed in the red bone marrow from giant cells - megakaryocytes. 1 μl of human blood normally contains 180-300 thousand platelets. A significant part of them is deposited in the spleen, liver, lungs, and, if necessary, enters the blood. An increase in the number of platelets in peripheral blood is called thrombocytosis, a decrease is called thrombocytopenia. The lifespan of platelets is 2-10 days.

Functions of platelets:

1. Participate in the process of blood clotting and dissolution of the blood clot (fibrinolysis).

2. Participate in stopping bleeding (hemostasis) due to the biologically active compounds present in them.

3. Perform a protective function due to the gluing (agglutination) of microbes and phagocytosis.

4. They produce some enzymes necessary for the normal functioning of platelets and for the process of stopping bleeding.

5. They transport creative substances that are important for preserving the structure of the vascular wall (without interaction with platelets, the vascular endothelium undergoes degeneration and begins to let red blood cells pass through it).

Blood coagulation system. Blood groups. Rh factor. Hemostasis and its mechanisms.

Hemostasis (Greek haime - blood, stasis - stationary state) is the cessation of blood movement through a blood vessel, i.e. stop bleeding. There are 2 mechanisms to stop bleeding:

1. Vascular-platelet hemostasis can independently stop bleeding from the most frequently injured small vessels with fairly low blood pressure in a few minutes. It consists of two processes:

Vascular spasm leading to a temporary stop or reduction of bleeding;

Formation, compaction and contraction of a platelet plug, leading to a complete stop of bleeding.

2. Coagulation hemostasis (blood clotting) ensures the cessation of blood loss when large vessels are damaged. Blood clotting is a protective reaction of the body. When wounded and blood leaks from the vessels, it changes from a liquid state to a jelly-like state. The resulting clot clogs the damaged vessels and prevents the loss of a significant amount of blood.

The concept of the Rh factor.

In addition to the ABO system (Landsteiner system), there is the Rh system, since in addition to the main agglutinogens A and B, erythrocytes may contain other additional ones, in particular, the so-called Rh agglutinogen (Rh factor). It was first discovered in 1940 by K. Landsteiner and I. Wiener in the blood of the rhesus monkey.

85% of people have the Rh factor in their blood. This blood is called Rh positive. Blood that lacks the Rh factor is called Rh negative. A special feature of the Rh factor is that people do not have anti-Rhesus agglutinins.

Blood groups.

Blood groups are a set of characteristics that characterize the antigenic structure of red blood cells and the specificity of anti-erythrocyte antibodies, which are taken into account when selecting blood for transfusions (from the Latin transfusio - transfusion).

Based on the presence of certain agglutinogens and agglutinins in the blood, people’s blood is divided into 4 groups, according to the Landsteiner ABO system.

Immunity, its types.

Immunity (from Latin immunitas - liberation from something, deliverance) is the body’s immunity to pathogens or poisons, as well as the body’s ability to protect itself from genetically foreign bodies and substances.

According to the method of origin they distinguish congenital And acquired immunity.

Innate (species) immunity is a hereditary trait for this type of animal (dogs and rabbits do not get polio).

Acquired immunity acquired in the process of life and is divided into naturally acquired and artificially acquired. Each of them, according to the method of occurrence, is divided into active and passive.

Naturally acquired active immunity occurs after suffering a corresponding infectious disease.

Naturally acquired passive immunity is caused by the transfer of protective antibodies from the mother’s blood through the placenta into the blood of the fetus. In this way, newborn children gain immunity against measles, scarlet fever, diphtheria and other infections. After 1-2 years, when the antibodies received from the mother are destroyed and partially released from the child’s body, his susceptibility to these infections increases sharply. Passive immunity can be transmitted to a lesser extent through mother's milk.

Artificially acquired immunity is reproduced by humans in order to prevent infectious diseases.

Active artificial immunity is achieved by inoculating healthy people with cultures of killed or weakened pathogenic microbes, weakened toxins or viruses. For the first time, artificial active immunization was performed by Jenner by inoculating children with cowpox. This procedure was called by Pasteur vaccination, and the grafting material was called vaccine (from the Latin vacca - cow).

Passive artificial immunity is reproduced by injecting a person with serum containing ready-made antibodies against microbes and their toxins. Antitoxic serums are especially effective against diphtheria, tetanus, gas gangrene, botulism, and snake venoms (cobra, viper, etc.). these sera are obtained mainly from horses, which are immunized with the corresponding toxin.

Depending on the direction of action, antitoxic, antimicrobial and antiviral immunity are also distinguished.

Antitoxic immunity is aimed at neutralizing microbial poisons, the leading role in it belongs to antitoxins.

Antimicrobial (antibacterial) immunity is aimed at destroying microbial bodies. Antibodies and phagocytes play a major role in this process.

Antiviral immunity is manifested by the formation in the cells of the lymphoid series of a special protein - interferon, which suppresses the reproduction of viruses

Blood- a fluid that circulates in the circulatory system and carries gases and other dissolved substances necessary for metabolism or formed as a result of metabolic processes.

Blood consists of plasma (a clear, pale yellow liquid) and cellular elements suspended in it. There are three main types of blood cells: red blood cells (erythrocytes), white blood cells (leukocytes) and platelets (platelets). The red color of blood is determined by the presence of the red pigment hemoglobin in red blood cells. In the arteries, through which blood entering the heart from the lungs is transported to the tissues of the body, hemoglobin is saturated with oxygen and colored bright red; in the veins through which blood flows from tissues to the heart, hemoglobin is practically devoid of oxygen and is darker in color.

Blood is a rather viscous liquid, and its viscosity is determined by the content of red blood cells and dissolved proteins. Blood viscosity greatly influences the speed at which blood flows through arteries (semi-elastic structures) and blood pressure. The fluidity of blood is also determined by its density and the pattern of movement of various types of cells. White blood cells, for example, move singly, in close proximity to the walls of blood vessels; red blood cells can move either individually or in groups like stacked coins, creating an axial, i.e. flow concentrated in the center of the vessel. An adult male's blood volume is approximately 75 ml per kilogram of body weight; in an adult woman this figure is approximately 66 ml. Accordingly, the total blood volume in an adult man is on average about 5 liters; more than half of the volume is plasma, and the rest is mainly erythrocytes.

Blood functions

The functions of the blood are much more complex than simply transporting nutrients and metabolic waste. Hormones that control many vital processes are also carried in the blood; blood regulates body temperature and protects the body from damage and infection in any part of it.

Transport function of blood. Almost all processes related to digestion and respiration - two body functions without which life is impossible - are closely related to blood and blood supply. The connection with breathing is expressed in the fact that blood ensures gas exchange in the lungs and transport of the corresponding gases: oxygen - from the lungs to the tissue, carbon dioxide (carbon dioxide) - from the tissues to the lungs. Transport of nutrients begins from the capillaries of the small intestine; here the blood captures them from the digestive tract and transports them to all organs and tissues, starting with the liver, where modification of nutrients (glucose, amino acids, fatty acids) occurs, and liver cells regulate their level in the blood depending on the needs of the body (tissue metabolism) . The transition of transported substances from blood to tissue occurs in tissue capillaries; at the same time, end products enter the blood from the tissues, which are then excreted through the kidneys with urine (for example, urea and uric acid). The blood also carries secretion products of the endocrine glands - hormones - and thereby ensures communication between various organs and coordination of their activities.

Body temperature regulation. Blood plays a key role in maintaining a constant body temperature in homeothermic, or warm-blooded, organisms. The temperature of the human body in a normal state fluctuates in a very narrow range of about 37 ° C. The release and absorption of heat by different parts of the body must be balanced, which is achieved by heat transfer through the blood. The center of temperature regulation is located in the hypothalamus, a part of the diencephalon. This center, being highly sensitive to small changes in the temperature of the blood passing through it, regulates those physiological processes in which heat is released or absorbed. One mechanism is to regulate heat loss through the skin by changing the diameter of the cutaneous blood vessels of the skin and, accordingly, the volume of blood flowing near the surface of the body, where heat is more easily lost. In the event of infection, certain waste products of microorganisms or products of tissue breakdown caused by them interact with white blood cells, causing the formation of chemicals that stimulate the center of temperature regulation in the brain. As a result, there is a rise in body temperature, felt as heat.

Protecting the body from damage and infection. In the implementation of this blood function, two types of leukocytes play a special role: polymorphonuclear neutrophils and monocytes. They rush to the site of injury and accumulate near it, with most of these cells migrating from the bloodstream through the walls of nearby blood vessels. They are attracted to the site of injury by chemicals released by damaged tissue. These cells are able to absorb bacteria and destroy them with their enzymes.

Thus, they prevent the spread of infection in the body.

Leukocytes also take part in the removal of dead or damaged tissue. The process of absorption by a cell of a bacterium or a fragment of dead tissue is called phagocytosis, and the neutrophils and monocytes that carry it out are called phagocytes. An actively phagocytic monocyte is called a macrophage, and a neutrophil is called a microphage. In the fight against infection, an important role is played by plasma proteins, namely immunoglobulins, which include many specific antibodies. Antibodies are formed by other types of leukocytes - lymphocytes and plasma cells, which are activated when specific antigens of bacterial or viral origin enter the body (or those present on cells foreign to the body). It may take several weeks for lymphocytes to produce antibodies against the antigen the body encounters for the first time, but the resulting immunity lasts a long time. Although the level of antibodies in the blood begins to fall slowly after a few months, upon repeated contact with the antigen it rises again quickly. This phenomenon is called immunological memory. P

When interacting with the antibody, microorganisms either stick together or become more vulnerable to absorption by phagocytes. In addition, antibodies prevent the virus from entering the host cells.

blood pH. pH is an indicator of the concentration of hydrogen (H) ions, numerically equal to the negative logarithm (denoted by the Latin letter “p”) of this value. The acidity and alkalinity of solutions are expressed in units of the pH scale, which ranges from 1 (strong acid) to 14 (strong alkali). Normally, the pH of arterial blood is 7.4, i.e. close to neutral. Venous blood is somewhat acidified due to carbon dioxide dissolved in it: carbon dioxide (CO2), formed during metabolic processes, when dissolved in the blood, reacts with water (H2O), forming carbonic acid (H2CO3).

Maintaining blood pH at a constant level, i.e., in other words, acid-base balance, is extremely important. So, if the pH drops noticeably, the activity of enzymes in the tissues decreases, which is dangerous for the body. Changes in blood pH beyond the range of 6.8-7.7 are incompatible with life. The kidneys, in particular, contribute to maintaining this indicator at a constant level, since they remove acids or urea (which gives an alkaline reaction) from the body as needed. On the other hand, pH is maintained by the presence in the plasma of certain proteins and electrolytes that have a buffering effect (that is, the ability to neutralize some excess acid or alkali).

Physicochemical properties of blood. The density of whole blood depends mainly on its content of red blood cells, proteins and lipids. The color of blood changes from scarlet to dark red depending on the ratio of oxygenated (scarlet) and non-oxygenated forms of hemoglobin, as well as the presence of hemoglobin derivatives - methemoglobin, carboxyhemoglobin, etc. The color of plasma depends on the presence of red and yellow pigments in it - mainly carotenoids and bilirubin, a large amount of which in pathology gives the plasma a yellow color. Blood is a colloidal polymer solution in which water is the solvent, salts and low-molecular organic plasma are the dissolved substances, and proteins and their complexes are the colloidal component. On the surface of blood cells there is a double layer of electrical charges, consisting of negative charges firmly bound to the membrane and a diffuse layer of positive charges balancing them. Due to the double electrical layer, an electrokinetic potential arises, which plays an important role in stabilizing cells, preventing their aggregation. As the ionic strength of the plasma increases due to the entry of multiply charged positive ions into it, the diffuse layer contracts and the barrier preventing cell aggregation decreases. One of the manifestations of blood microheterogeneity is the phenomenon of erythrocyte sedimentation. It lies in the fact that in the blood outside the bloodstream (if its coagulation is prevented), the cells settle (sediment), leaving a layer of plasma on top.

Erythrocyte sedimentation rate (ESR) increases in various diseases, mainly of an inflammatory nature, due to changes in the protein composition of plasma. The sedimentation of erythrocytes is preceded by their aggregation with the formation of certain structures such as coin columns. The ESR depends on how their formation proceeds. The concentration of plasma hydrogen ions is expressed in hydrogen index values, i.e. negative logarithm of hydrogen ion activity. The average blood pH is 7.4. Maintaining the constancy of this value is a great physiol. significance, since it determines the rates of many chemicals. and physical-chemical processes in the body.

Normally, the pH of arterial K is 7.35-7.47; venous blood is 0.02 lower; the content of erythrocytes is usually 0.1-0.2 more acidic than plasma. One of the most important properties of blood - fluidity - is the subject of study of biorheology. In the bloodstream, blood normally behaves like a non-Newtonian fluid, changing its viscosity depending on flow conditions. In this regard, the viscosity of blood in large vessels and capillaries varies significantly, and the viscosity data given in the literature is conditional. The patterns of blood flow (blood rheology) have not been sufficiently studied. The non-Newtonian behavior of blood is explained by the high volume concentration of blood cells, their asymmetry, the presence of proteins in the plasma and other factors. Measured on capillary viscometers (with a capillary diameter of several tenths of a millimeter), the viscosity of blood is 4-5 times higher than the viscosity of water.

In pathology and injury, blood fluidity changes significantly due to the action of certain factors of the blood coagulation system. Basically, the work of this system consists in the enzymatic synthesis of a linear polymer - fabrin, which forms a network structure and gives the blood the properties of jelly. This “jelly” has a viscosity that is hundreds and thousands higher than the viscosity of blood in a liquid state, exhibits strength properties and high adhesive ability, which allows the clot to stay on the wound and protect it from mechanical damage. The formation of clots on the walls of blood vessels when the balance in the coagulation system is disturbed is one of the causes of thrombosis. The formation of a fibrin clot is prevented by the anticoagulation system; the destruction of the formed clots occurs under the action of the fibrinolytic system. The resulting fibrin clot initially has a loose structure, then becomes denser, and retraction of the clot occurs.

Blood components

Plasma. After the separation of cellular elements suspended in the blood, an aqueous solution of complex composition remains, called plasma. As a rule, plasma is a clear or slightly opalescent liquid, the yellowish color of which is determined by the presence of small amounts of bile pigment and other colored organic substances. However, after consuming fatty foods, many fat droplets (chylomicrons) enter the bloodstream, causing the plasma to become cloudy and oily. Plasma is involved in many vital processes of the body. It transports blood cells, nutrients and metabolic products and serves as a link between all extravascular (i.e., located outside the blood vessels) fluids; the latter include, in particular, the intercellular fluid, and through it communication with the cells and their contents occurs.

Thus, the plasma comes into contact with the kidneys, liver and other organs and thereby maintains the constancy of the internal environment of the body, i.e. homeostasis. The main plasma components and their concentrations are shown in the table. Among the substances dissolved in plasma are low molecular weight organic compounds (urea, uric acid, amino acids, etc.); large and very complex protein molecules; partially ionized inorganic salts. The most important cations (positively charged ions) include sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+); The most important anions (negatively charged ions) are chloride anions (Cl-), bicarbonate (HCO3-) and phosphate (HPO42- or H2PO4-). The main protein components of plasma are albumin, globulins and fibrinogen.

Plasma proteins. Of all proteins, albumin, synthesized in the liver, is present in the highest concentration in plasma. It is necessary to maintain osmotic balance, ensuring normal distribution of fluid between blood vessels and the extravascular space. During fasting or insufficient protein intake from food, the albumin content in plasma decreases, which can lead to increased accumulation of water in tissues (edema). This condition, associated with protein deficiency, is called starvation edema. Plasma contains several types or classes of globulins, the most important of which are designated by the Greek letters a (alpha), b (beta) and g (gamma), and the corresponding proteins are a1, a2, b, g1 and g2. After separation of globulins (by electrophoresis), antibodies are detected only in fractions g1, g2 and b. Although antibodies are often called gamma globulins, the fact that some of them are also present in the b-fraction led to the introduction of the term “immunoglobulin”. The a- and b-fractions contain many different proteins that provide transport in the blood of iron, vitamin B12, steroids and other hormones. This same group of proteins also includes coagulation factors, which, along with fibrinogen, are involved in the process of blood clotting. The main function of fibrinogen is to form blood clots (thrombi). During the process of blood clotting, whether in vivo (in a living body) or in vitro (outside the body), fibrinogen is converted into fibrin, which forms the basis of a blood clot; Plasma that does not contain fibrinogen, usually in the form of a clear, pale yellow liquid, is called blood serum.

Red blood cells. Red blood cells, or erythrocytes, are round discs with a diameter of 7.2-7.9 µm and an average thickness of 2 µm (µm = micron = 1/106 m). 1 mm3 of blood contains 5-6 million red blood cells. They make up 44-48% of the total blood volume. Red blood cells have the shape of a biconcave disc, i.e. The flat sides of the disk are compressed, making it look like a donut without a hole. Mature red blood cells do not have nuclei. They contain mainly hemoglobin, the concentration of which in the intracellular aqueous environment is about 34%. [In terms of dry weight, the hemoglobin content in erythrocytes is 95%; per 100 ml of blood, the hemoglobin content is normally 12-16 g (12-16 g%), and in men it is slightly higher than in women.] In addition to hemoglobin, red blood cells contain dissolved inorganic ions (mainly K+) and various enzymes. The two concave sides provide the red blood cell with optimal surface area through which gases can be exchanged: carbon dioxide and oxygen.

Thus, the shape of cells largely determines the efficiency of physiological processes. In humans, the surface area through which gas exchange occurs is on average 3820 m2, which is 2000 times the surface of the body. In the fetus, primitive red blood cells are first formed in the liver, spleen and thymus. From the fifth month of intrauterine development, erythropoiesis gradually begins in the bone marrow - the formation of full-fledged red blood cells. In exceptional circumstances (for example, when normal bone marrow is replaced by cancerous tissue), the adult body can switch back to producing red blood cells in the liver and spleen. However, under normal conditions, erythropoiesis in an adult occurs only in flat bones (ribs, sternum, pelvic bones, skull and spine).

Red blood cells develop from precursor cells, the source of which is the so-called. stem cells. In the early stages of red blood cell formation (in cells still in the bone marrow), the cell nucleus is clearly visible. As the cell matures, hemoglobin accumulates, formed during enzymatic reactions. Before entering the bloodstream, the cell loses its nucleus due to extrusion (squeezing out) or destruction by cellular enzymes. With significant blood loss, red blood cells are formed faster than normal, and in this case, immature forms containing a nucleus may enter the bloodstream; This apparently occurs because the cells leave the bone marrow too quickly.

The period of maturation of erythrocytes in the bone marrow - from the moment the youngest cell appears, recognizable as the precursor of an erythrocyte, to its full maturation - is 4-5 days. The lifespan of a mature erythrocyte in peripheral blood is on average 120 days. However, with certain abnormalities of the cells themselves, a number of diseases, or under the influence of certain medications, the lifespan of red blood cells can be shortened. Most of the red blood cells are destroyed in the liver and spleen; in this case, hemoglobin is released and breaks down into its components heme and globin. The further fate of globin was not traced; As for heme, iron ions are released from it (and returned to the bone marrow). Losing iron, heme turns into bilirubin - a red-brown bile pigment. After minor modifications occurring in the liver, bilirubin in bile is excreted through the gallbladder into the digestive tract. Based on the content of the final product of its transformations in feces, the rate of destruction of red blood cells can be calculated. On average, in an adult body, 200 billion red blood cells are destroyed and re-formed every day, which is approximately 0.8% of their total number (25 trillion).

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

The degree of binding of oxygen to hemoglobin depends primarily on the concentration of oxygen dissolved in the plasma. In the lungs, where there is a lot of oxygen, it diffuses from the pulmonary alveoli through the walls of blood vessels and the aqueous medium of the plasma and enters the red blood cells; there it binds to hemoglobin - oxyhemoglobin is formed. In tissues where the oxygen concentration is low, oxygen molecules are separated from hemoglobin and penetrate into the tissue due to diffusion. Insufficiency of red blood cells or hemoglobin leads to a decrease in oxygen transport and thereby to disruption of biological processes in tissues. In humans, a distinction is made between fetal hemoglobin (type F, from fetus) and adult hemoglobin (type A, from adult). There are many known genetic variants of hemoglobin, the formation of which leads to abnormalities of red blood cells or their function. Among them, the most famous is hemoglobin S, which causes sickle cell anemia.

Leukocytes. White peripheral blood cells, or leukocytes, are divided into two classes depending on the presence or absence of special granules in their cytoplasm. Cells that do not contain granules (agranulocytes) are lymphocytes and monocytes; their kernels have a predominantly regular round shape. Cells with specific granules (granulocytes) are usually characterized by the presence of irregularly shaped nuclei with many lobes and are therefore called polymorphonuclear leukocytes. They are divided into three types: neutrophils, basophils and eosinophils. They differ from each other in the pattern of granules stained with various dyes. In a healthy person, 1 mm3 of blood contains from 4000 to 10,000 leukocytes (on average about 6000), which is 0.5-1% of blood volume. The proportion of individual types of cells in the composition of white blood cells can vary significantly between different people and even within the same person at different times.

Polymorphonuclear leukocytes(neutrophils, eosinophils and basophils) are formed in the bone marrow from precursor cells, which give rise to stem cells, probably the same ones that give rise to the precursors of red blood cells. As the nucleus matures, the cells develop granules that are typical for each cell type. In the bloodstream, these cells move along the walls of the capillaries primarily due to amoeboid movements. Neutrophils are able to leave the internal space of the vessel and accumulate at the site of infection. The lifespan of granulocytes appears to be about 10 days, after which they are destroyed in the spleen. The diameter of neutrophils is 12-14 microns. Most dyes color their core purple; the nucleus of peripheral blood neutrophils can have from one to five lobes. The cytoplasm is stained pinkish; under a microscope, many intense pink granules can be distinguished in it. In women, approximately 1% of neutrophils carry sex chromatin (formed by one of the two X chromosomes), a drumstick-shaped body attached to one of the nuclear lobes. These so-called Barr bodies allow sex to be determined by examining blood samples. Eosinophils are similar in size to neutrophils. Their nucleus rarely has more than three lobes, and the cytoplasm contains many large granules, which clearly stain bright red with eosin dye. Unlike eosinophils, basophils have cytoplasmic granules stained blue with basic dyes.

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

Lymphocytes. These are small mononuclear cells. Most peripheral blood lymphocytes have a diameter of less than 10 µm, but lymphocytes with a larger diameter (16 µm) are sometimes found. The cell nuclei are dense and round, the cytoplasm is bluish in color, with very sparse granules. Although lymphocytes appear morphologically uniform, they differ clearly in their functions and cell membrane properties. They are divided into three broad categories: B cells, T cells, and O cells (null cells, or neither B nor T). B lymphocytes mature in the human bone marrow and then migrate to the lymphoid organs. They serve as precursors to cells that form antibodies, the so-called. plasmatic. In order for B cells to transform into plasma cells, the presence of T cells is necessary. T cell maturation begins in the bone marrow, where prothymocytes are formed, which then migrate to the thymus (thymus gland), an organ located in the chest behind the breastbone. There they differentiate into T lymphocytes, a highly heterogeneous population of immune system cells that perform various functions. Thus, they synthesize macrophage activation factors, B-cell growth factors and interferons. Among T cells there are inducer (helper) cells that stimulate the formation of antibodies by B cells. There are also suppressor cells that suppress the functions of B cells and synthesize the growth factor of T cells - interleukin-2 (one of the lymphokines). O cells differ from B and T cells in that they do not have surface antigens. Some of them serve as “natural killers”, i.e. kill cancer cells and cells infected with a virus. However, the overall role of O cells is unclear.

Platelets They are colorless, nuclear-free bodies of spherical, oval or rod-shaped shape with a diameter of 2-4 microns. Normally, the platelet content in peripheral blood is 200,000-400,000 per 1 mm3. Their lifespan is 8-10 days. Standard dyes (azur-eosin) give them a uniform pale pink color. Using electron microscopy, it was shown that the structure of the cytoplasm of platelets is similar to ordinary cells; however, they are not actually cells, but fragments of the cytoplasm of very large cells (megakaryocytes) present in the bone marrow. Megakaryocytes are derived from the descendants of the same stem cells that give rise to red and white blood cells. As will be discussed in the next section, platelets play a key role in blood clotting. Damage to the bone marrow due to drugs, ionizing radiation, or cancer can lead to a significant decrease in the platelet count in the blood, which causes spontaneous hematomas and bleeding.

Blood clotting Blood clotting, or coagulation, is the process of turning liquid blood into an elastic clot (thrombus). Blood clotting at the site of injury is a vital reaction that stops bleeding. However, the same process also underlies vascular thrombosis - an extremely unfavorable phenomenon in which a complete or partial blockage of their lumen occurs, preventing blood flow.

Hemostasis (stopping bleeding). When a thin or even medium-sized blood vessel is damaged, for example by cutting or squeezing tissue, internal or external bleeding (hemorrhage) occurs. As a rule, bleeding stops due to the formation of a blood clot at the site of injury. A few seconds after injury, the lumen of the vessel contracts in response to the action of released chemicals and nerve impulses. When the endothelial lining of blood vessels is damaged, the collagen located under the endothelium is exposed, to which platelets circulating in the blood quickly adhere. They release chemicals that cause blood vessels to narrow (vasoconstrictors). Platelets also secrete other substances that participate in a complex chain of reactions leading to the conversion of fibrinogen (a soluble blood protein) into insoluble fibrin. Fibrin forms a blood clot, the threads of which trap blood cells. One of the most important properties of fibrin is its ability to polymerize to form long fibers that compress and push blood serum out of the clot.

Thrombosis- abnormal blood clotting in arteries or veins. As a result of arterial thrombosis, blood flow to the tissues deteriorates, which causes their damage. This occurs with myocardial infarction caused by thrombosis of a coronary artery, or with a stroke caused by thrombosis of cerebral vessels. Vein thrombosis prevents the normal flow of blood from tissues. When a large vein is blocked by a blood clot, swelling occurs near the site of the blockage, which sometimes spreads, for example, to the entire limb. It happens that part of the venous thrombus breaks off and enters the bloodstream in the form of a moving clot (embolus), which over time can end up in the heart or lungs and lead to life-threatening circulatory problems.

Several factors have been identified that predispose to intravascular thrombus formation; These include:

1. slowing of venous blood flow due to low physical activity;
2. vascular changes caused by increased blood pressure;
3. local hardening of the inner surface of blood vessels due to inflammatory processes or - in the case of arteries - due to the so-called. atheromatosis (lipid deposits on artery walls);
4. increased blood viscosity due to polycythemia (increased levels of red blood cells in the blood);
5. an increase in the number of platelets in the blood.

Studies have shown that the last of these factors plays a special role in the development of thrombosis. The fact is that a number of substances contained in platelets stimulate the formation of a blood clot, and therefore any influences that cause platelet damage can accelerate this process. When damaged, the platelet surface becomes more sticky, causing them to stick together (aggregate) and release their contents. The endothelial lining of blood vessels contains the so-called. prostacyclin, which suppresses the release of the thrombogenic substance, thromboxane A2, from platelets. Other plasma components also play an important role, preventing thrombus formation in blood vessels by suppressing a number of enzymes of the blood coagulation system. Attempts to prevent thrombosis have so far yielded only partial results. Preventive measures include regular exercise, lowering high blood pressure and anticoagulant treatment; After surgery, it is recommended to start walking as early as possible. It should be noted that daily intake of aspirin, even in a small dose (300 mg), reduces platelet aggregation and significantly reduces the likelihood of thrombosis.

Blood transfusion Since the late 1930s, transfusion of blood or its individual fractions has become widespread in medicine, especially in the military. The main purpose of blood transfusion (hemotransfusion) is to replace the patient's red blood cells and restore blood volume after massive blood loss. The latter can occur either spontaneously (for example, with a duodenal ulcer), or as a result of injury, during surgery or during childbirth. Blood transfusions are also used to restore the level of red blood cells in some anemias, when the body loses the ability to produce new blood cells at the rate required for normal functioning. The general opinion of medical authorities is that blood transfusions should be performed only when strictly necessary, since they are associated with the risk of complications and transmission of an infectious disease to the patient - hepatitis, malaria or AIDS.

Blood typing. Before transfusion, the compatibility of the blood of the donor and the recipient is determined, for which blood typing is performed. Currently, typing is carried out by qualified specialists. A small amount of red blood cells is added to an antiserum containing large amounts of antibodies to specific red blood cell antigens. Antiserum is obtained from the blood of donors specially immunized with the corresponding blood antigens. Red blood cell agglutination is observed with the naked eye or under a microscope. The table shows how anti-A and anti-B antibodies can be used to determine ABO blood groups. As an additional in vitro test, you can mix donor red blood cells with recipient serum and, conversely, donor serum with recipient red blood cells - and see if there is any agglutination. This test is called cross-typing. If even a small number of cells agglutinate when mixing donor red blood cells and recipient serum, the blood is considered incompatible.

Blood transfusion and storage. The original methods of direct blood transfusion from donor to recipient are a thing of the past. Today, donor blood is taken from a vein under sterile conditions into specially prepared containers, into which an anticoagulant and glucose are previously added (the latter as a nutrient medium for red blood cells during storage). The most commonly used anticoagulant is sodium citrate, which binds calcium ions in the blood, which are necessary for blood clotting. Liquid blood is stored at 4°C for up to three weeks; During this time, 70% of the initial number of viable red blood cells remains. Since this level of living red blood cells is considered the minimum acceptable, blood stored for more than three weeks is not used for transfusion. With the growing need for blood transfusions, methods have emerged to keep red blood cells alive for longer periods of time. In the presence of glycerin and other substances, red blood cells can be stored indefinitely at temperatures from -20 to -197 ° C. For storage at -197 ° C, metal containers with liquid nitrogen are used, into which containers with blood are immersed. Blood that has been frozen is successfully used for transfusion. Freezing allows not only to create reserves of regular blood, but also to collect and store rare blood groups in special blood banks (storages).

Previously, blood was stored in glass containers, but now mostly plastic containers are used for this purpose. One of the main advantages of the plastic bag is that several bags can be attached to one anticoagulant container, and then using differential centrifugation in a “closed” system, all three types of cells and plasma can be separated from the blood. This very important innovation radically changed the approach to blood transfusion.

Today they are already talking about component therapy, when by transfusion we mean replacing only those blood elements that the recipient needs. Most people with anemia only need whole red blood cells; patients with leukemia require mainly platelets; hemophiliacs require only certain plasma components. All these fractions can be isolated from the same donor blood, after which only albumin and gamma globulin will remain (both have their own areas of application). Whole blood is used only to compensate for very large blood loss, and is now used for transfusion in less than 25% of cases.

Blood banks. In all developed countries, a network of blood transfusion stations has been created, which provide civil medicine with the necessary amount of blood for transfusion. At stations, as a rule, they only collect donor blood and store it in blood banks (storages). The latter provide hospitals and clinics with blood of the required type upon request. In addition, they usually have a special service that is responsible for obtaining both plasma and individual fractions (for example, gamma globulin) from expired whole blood. Many banks also have qualified specialists who perform full blood typing and study possible incompatibility reactions.

Composition and functions of blood

Blood is a liquid connective tissue consisting of liquid intercellular substance - plasma (50-60%) and formed elements (40-45%) - erythrocytes, leukocytes and platelets.

Plasma contains 90-92% water, 7-8% proteins, 0.12% glucose, up to 0.8% fats, 0.9% salts. The most important are sodium, potassium and calcium salts. Plasma proteins perform the following functions: maintain osmotic pressure, water metabolism, give blood viscosity, participate in blood clotting (fibrinogen) and immune reactions (antibodies). Plasma that lacks the fibrinogen protein is called serum.

In addition to the above components, plasma contains amino acids, vitamins, and hormones.

Erythrocytes are red, anucleate blood cells that look like a biconcave disc. This form increases the surface of red blood cells, and this contributes to the rapid and uniform penetration of oxygen through their membrane. Red blood cells contain a specific blood pigment - hemoglobin. Red blood cells are produced in red bone marrow. There are about 5.5 million red blood cells in 1 mm3 of blood. The function of red blood cells is to transport O2 and CO2, maintaining a constant internal environment of the body. A decrease in the number of red blood cells and a decrease in hemoglobin content leads to the development of anemia.

For some diseases and blood loss, blood transfusions are given. One person's blood is not always compatible with another's. There are four blood types in humans. Blood groups depend on protein substances: aglutinogens (in red blood cells) and agglutinins (in plasma). Agglutination - the gluing of red blood cells, occurs when agglutinins and aglutinogens of the same group are simultaneously present in the blood. When transfusing blood, the Rh factor is taken into account.

Leukocytes are white blood cells that do not have a permanent shape, contain a nucleus and are capable of amoeboid movement. The blood contains several types of leukocytes. There are 5-8 thousand leukocytes in 1 mm3 of blood. They are formed in the red bone marrow, spleen, and lymph nodes. Their content increases after eating, during inflammatory processes. Due to the ability of amoeboid movement, leukocytes can penetrate through the walls of capillaries to sites of infection in tissues and phagocytose microorganisms. Irritants for the movement of leukocytes are substances secreted by microorganisms.

Leukocytes constitute one of the important links in the body's defense mechanisms. The number of leukocytes is constant, therefore, their deviation from the physiological norm indicates the presence of a disease. The system of physiological processes that preserve the genetic stability of cells, protect the body from infectious diseases, is called immunity. Phagocytosis and antibody formation form the basis of immunity. Chemical substances and living organisms foreign to the body that cause the appearance of antibodies are called antigens.

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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, salty taste with a specific gravity of 1.054-1.066. The total amount of blood in an adult is on average about 5 liters (equal to 1/13 of body weight). Together with tissue fluid and lymph, it forms the internal environment of the body. Blood performs many 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 tissues and back; oxygen storage (respiratory function);

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

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

Blood clotting, preventing blood loss;

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

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

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

Blood, like liquid tissue, ensures the constancy of the internal environment of the body. Biochemical blood parameters 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 ensures the interconnection of metabolic processes occurring in various organs and tissues and performs various functions.

The relative constancy of the composition and properties of blood is a necessary and indispensable condition for the life of all tissues of the body. In humans and warm-blooded animals, metabolism in cells, between cells and tissue fluid, and also 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 associated changes in the composition and properties of the 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 formed 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 stands in a test tube or is centrifuged at low speeds, its formed elements precipitate.

Spontaneous precipitation of blood cells is called the erythrocyte sedimentation reaction (ERR, now ESR). The ESR value (mm/hour) for different animal species varies widely: if for a dog the ESR practically coincides with the range of values ​​for humans (2-10 mm/hour), then for a pig and a horse it does not exceed 30 and 64, respectively. Blood plasma devoid of 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 (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 tissue. Plasma consists of water in which substances (mineral and organic) are dissolved, including proteins (albumin, globulins and fibrinogen). Carbohydrates (glucose), fats (lipids), hormones, enzymes, vitamins, individual salt components (ions) and some metabolic products.

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

Blood composition: blood cells

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

erythrocytes (red blood cells);

leukocytes (white blood cells);

platelets (blood platelets).

Erythrocytes are red blood cells. Transport oxygen from the lungs to all human organs. It is red blood cells that contain iron-containing protein - bright red hemoglobin, which absorbs oxygen from the inhaled air 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 human body’s ability to resist various viruses and infections. There are different types of white blood cells. Some of them are aimed directly at destroying bacteria or various foreign cells that have entered the body. Others are involved in the production of special molecules, so-called antibodies, which are also necessary to fight various infections.

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

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, 1 μl of blood contains 180-320 * 109/l blood platelets (platelets). Normally, the cell volume is 35-45% of the total blood volume.

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 influencing blood composition are quite diverse. Therefore, in order to correctly read test results, a doctor needs to know about a person’s bad habits and physical activity, and even about their diet. Even the environment affects the composition of the blood. Everything related to metabolism also affects blood counts. For example, you can consider how a normal meal changes blood counts:

Eating before a blood test will increase the concentration of fats.

Fasting for 2 days will increase bilirubin in the blood.

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

Fatty foods will increase potassium and triglyceride levels.

Excessive consumption of meat will increase urate levels.

Coffee increases the levels of glucose, fatty acids, white blood cells and red blood cells.

The blood of smokers is significantly different from the blood of people leading a healthy lifestyle. However, if you lead an active lifestyle, you should reduce the intensity of your workouts before taking a blood test. This is especially true when taking hormone tests. Various medications also affect the chemical composition of the blood, so if you have taken anything, be sure to tell your doctor.

2. Blood plasma

Blood plasma is the liquid part of the blood in which 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 metabolic products return back.

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

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

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

Blood proteins: albumin

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

Based on the shape and size of the molecules, blood proteins are divided into albumins and globulins. The most common protein in blood plasma is albumin (more than 50% of all proteins, 40-50 g/l). They act as transport proteins for some hormones, free fatty acids, bilirubin, various ions and medications, maintain the constancy of colloid-osmotic 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 for a number of diseases. When the concentration of albumin in the blood is low, the balance between the blood plasma and the intercellular fluid is disturbed. The latter stops entering the blood, and swelling 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 loss (for example, through ulcerated mucous membrane of the gastrointestinal tract). In old age and old age, the albumin content decreases. Measuring plasma albumin concentrations is used as a test of liver function because chronic liver diseases are characterized by low albumin concentrations due to decreased albumin synthesis and increased volume of distribution as a result of fluid retention in the body.

Low albumin levels (hypoalbuminemia) in newborns increase the risk of jaundice because albumin binds free bilirubin in the blood. Albumin also binds many drugs entering the bloodstream, so when its concentration decreases, the risk of poisoning from an unbound substance increases. Analbuminemia is a rare hereditary disease in which the plasma albumin concentration is very low (250 mg/L or less). Individuals with these disorders are susceptible to occasional mild edema without any other clinical symptoms. High concentrations of albumin in the blood (hyperalbuminemia) can be caused by either excess albumin infusion or dehydration of the body.

Immunoglobulins

Most other blood plasma proteins are classified as globulins. Among them are: a-globulins, which bind thyroxine and bilirubin; b-globulins that bind iron, cholesterol and vitamins A, D and K; g-globulins, which bind histamine and play an important role in the body’s immunological reactions, therefore they are also called immunoglobulins or antibodies. There are 5 main classes of immunoglobulins, the most common of which are IgG, IgA, and IgM. A decrease or 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 a consequence of the use of cytostatic drugs or with significant protein losses (nephrotic syndrome). In the complete absence of immunoglobulins, for example, in AIDS, recurrent bacterial infections can develop.

Increased concentrations of immunoglobulins are observed in acute and chronic infectious, as well as autoimmune diseases, for example, rheumatism, systemic lupus erythematosus, etc. The identification of immunoglobulins to specific antigens (immunodiagnostics) provides significant assistance in making the diagnosis of many infectious diseases.

Other plasma proteins

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

Globulins include plasma proteins involved in blood clotting, such as prothrombin and fibrinogen, and determining their concentrations is important when evaluating 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 body position (within 30 minutes after moving from a supine to a vertical position, the concentration of proteins in plasma increases by 10-20%) or after applying venipuncture tourniquet (protein concentration may increase within a few minutes). In both cases, the increase in protein concentration is caused by increased diffusion of fluid from the vessels into the intercellular space and a decrease in the volume of their distribution (dehydration effect). In contrast, a rapid decrease in protein concentration is most often a consequence of an increase in plasma volume, for example, with an increase in capillary permeability in patients with generalized inflammation.

Other blood 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, and enzymes involved in metabolic processes. The blood plasma contains waste products of the body that must be removed, such as urea, uric acid, creatinine, bilirubin, etc. They are transported through the bloodstream to the kidneys. The concentration of waste products in the blood has its own permissible limits. An increase in the concentration of uric acid can be observed with gout, the use of diuretics, as a result of decreased renal 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, in shock, etc., decrease in liver failure, nephrotic syndrome, etc.

Blood plasma also contains minerals - 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 jointly participate in the regulation of osmotic pressure, blood pH, and a number of other processes. For example, calcium ions affect the colloidal state of cellular contents, participate in the process of blood clotting, and 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 - container, 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 with a diameter of 3-4 microns, surrounded by a membrane and usually lacking a nucleus. They contain large quantities of mitochondria, elements of the Golgi complex, ribosomes, as well as granules of various shapes and sizes containing glycogen, enzymes (fibronectin, fibrinogen), platelet-derived 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 are activated, become spherical and acquire the ability for adhesion - sticking to the wall of the vessel, and aggregation - sticking to each other. The resulting thrombus restores the integrity of the vessel walls. 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 in leukemia, aplastic anemia, alcoholism, etc. Impaired platelet function can be caused by 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 - container, here - cell) are highly specific blood cells of animals and humans, containing hemoglobin.

The diameter of an individual red blood cell is 7.2-7.5 microns, the thickness is 2.2 microns, and the volume is about 90 microns3. The total surface of all red blood cells reaches 3000 m2, which is 1500 times greater than the surface of the human body. Such a large surface of red blood cells is due to their large number and unique shape. They have the shape of a biconcave disk and, when viewed in cross section, resemble dumbbells. With this shape, there is not a single point in red blood cells that is more than 0.85 microns from the surface. Such ratios of surface and volume contribute to the optimal performance of the main function of red blood cells - 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, red blood cells lack a nucleus and have the shape of biconcave discs. The specific shape of red blood cells results in a higher surface-to-volume ratio, which increases the possibility of gas exchange. In sharks, frogs and birds, red blood cells are oval or round in shape and contain nuclei. The average diameter of human red blood cells is 7-8 microns, which is approximately equal to the diameter of blood capillaries. An erythrocyte is capable of “folding” when passing through capillaries, the lumen of which is smaller than the diameter of the erythrocyte.

Red blood cells

In the capillaries of the pulmonary 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 red blood cell 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 inhaling carbon monoxide, a person quickly collapses and may die from suffocation. Hemoglobin also carries out the transfer of carbon dioxide. The enzyme carbonic anhydrase contained in erythrocytes also participates in its transport.

Hemoglobin

Human red blood cells, like those of all mammals, have the shape of a biconcave disc and contain hemoglobin.

Hemoglobin is the main component of red blood cells and provides the respiratory function of blood, being a respiratory pigment. It is found inside red blood cells and not in the blood plasma, which reduces 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 globin protein and 4 molecules of the iron-containing compound heme. The heme iron atom is capable of attaching and donating 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% hemoglobin (145 g/l). This value can range 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 bone marrow cells. When red blood cells are destroyed after heme is separated, hemoglobin is converted into the bile pigment bilirubin, which enters the intestine with bile and, after transformation, 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 that 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. It helps to carry out gas exchange 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 copper rather than iron. In some annelids, oxygen transfer is carried out using hemerythrin or chlorocruorin.

Formation, destruction and pathology of red blood cells

The process of formation of red blood cells (erythropoiesis) occurs in the red bone marrow. Immature red blood cells (reticulocytes), entering the bloodstream from the bone marrow, contain cellular organelles - ribosomes, mitochondria and the Golgi apparatus. Reticulocytes make up about 1% of all circulating red blood cells. Their final differentiation occurs within 24-48 hours after release into the bloodstream. The rate of breakdown of red blood cells 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 high oxygen levels, the opposite picture is observed.

The blood of men contains on average 5x1012/l of red blood cells (6,000,000 in 1 μl), in women - about 4.5x1012/l (4,500,000 in 1 μl). This number of red blood cells, arranged in a chain, will circle the globe along the equator 5 times.

The higher content of red blood cells in men is associated with the influence of male sex hormones - androgens, which stimulate the formation of red blood cells. 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, and can occur with 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, heterogeneity of red blood cells in size and shape is noted, in particular, with iron deficiency anemia in pregnant women.

Sometimes an atom of ferric iron is included in the heme instead of divalent, and methemoglobin is formed, which binds oxygen so tightly that it is not able to release 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 red blood cells is accompanied by a change in their shape. In the peripheral blood of healthy people, the number of regularly shaped red blood cells (discocytes) is 85% of their total number.

Hemolysis is the destruction of the membrane of red blood cells, accompanied by the release of hemoglobin 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 unfavorable microenvironmental factors (for example, toxins of inorganic or organic nature). During hemolysis, the contents of the red blood cell 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 a number of cases, so-called biological hemolysis can be observed, which develops during transfusion of incompatible blood, with the bites of certain snakes, under the influence of immune hemolysins, etc.

As a red blood cell ages, 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 subsequently be reused in the formation of new red blood cells. The rest of the heme is broken down to form the bile pigments bilirubin and biliverdin. Both pigments are eventually excreted through bile into the intestines.

Erythrocyte sedimentation rate (ESR)

If you add anti-clotting substances to a test tube with blood, you can study its most important indicator - the erythrocyte sedimentation rate. To study ESR, blood is mixed with a solution of sodium citrate and drawn into a glass tube with millimeter graduations. After an hour, the height of the upper transparent layer is counted.

Normal erythrocyte sedimentation in men is 1-10 mm per hour, in women it is 2-5 mm per hour. An increase in sedimentation rate greater than the specified values ​​is a sign of pathology.

The value of ESR depends on the properties of 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, so in such patients the ESR usually exceeds the norm.

In the clinic, the state of the human body is judged by the erythrocyte sedimentation rate (ESR). Normal ESR in men is 1-10 mm/hour, in women 2-15 mm/hour. An increase in ESR is a highly sensitive but nonspecific 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 in various erythrocytoses.

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 towards the end of the day, with physical activity, emotional stress, intake of protein foods, sudden changes in temperature environment.

There are two main groups of leukocytes - granulocytes (granular leukocytes) and agranulocytes (non-granular leukocytes). Granulocytes are divided 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 connected to each other by thin threads. Depending on the degree of differentiation, band neutrophils (immature forms with horseshoe-shaped nuclei) and segmented (mature) neutrophils are distinguished. In women, one of the segments of the nucleus contains a drumstick-shaped outgrowth - the so-called Barr body. The cytoplasm is filled with many small granules. Neutrophils contain mitochondria and large amounts of glycogen. The lifespan 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 debris and other material to be removed, the specific recognition of which is carried out using receptors. After phagocytosis, neutrophils die, and their remains constitute 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, arachidonic acid metabolites, 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 damage (see Inflammation).

Eosinophils

Basophils

Basophils make up 0-1% of the leukocyte population. Size 10-12 microns. Most often they have a trilobed S-shaped nucleus and contain all types of organelles, free ribosomes and glycogen. Cytoplasmic granules are stained blue with basic dyes (methylene blue, etc.), which explains 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 for amoeboid movement is limited. Life expectancy 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; the cytoplasm contains typical organelles, phagocytic vacuoles, and numerous lysosomes. Various substances formed at sites 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. The cytoplasm contains few lysosomes, mitochondria, a minimum of endoplasmic reticulum, and quite a lot of free ribosomes. There are 2 morphologically similar, but functionally different groups of lymphocytes: T-lymphocytes (80%), formed in the thymus (thymus gland), and B-lymphocytes (10%), formed in lymphoid tissue. Lymphocyte cells form short processes (microvilli), which are 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 during a viral infection). The lifespan of lymphocytes varies from several days to ten or more years.

Anemia is a decrease in red blood cell mass. Because blood volume is usually maintained at a constant level, the degree of anemia can be determined either by the volume of red blood cells expressed as a percentage of the total blood volume (hematocrit [BG]) or by 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 oxygen tension is lower than usual, the values ​​of red blood indicators increase.

In women, anemia is indicated by a hemoglobin content in the blood (Hb) less than 120 g/l and a hematocrit (Ht) below 36%. In men, the occurrence of anemia is detected with Nb< 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 decrease in the oxygen capacity of the blood due to a decrease in the number of circulating red blood cells, 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 minute volume, despite its low oxygen capacity.

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

RI = 0.5 x (reticulocyte content x patient's Ht/normal Ht).

An RI exceeding a level of 2-3% indicates an adequate response to intensify erythropoiesis in response to anemia. A smaller value indicates inhibition of the formation of red blood cells by the bone marrow as the cause of anemia. Determining the average erythrocyte volume is used to classify a patient’s anemia into one of three groups: a) microcytic; b) normocytic; c) macrocytic. Normocytic anemia is characterized by a normal volume of red blood cells; in microcytic anemia it is reduced, and in macrocytic anemia it is increased.

The normal range of fluctuations in the average erythrocyte volume is 80-98 µm3. Anemia at a specific and individual level for each patient of hemoglobin concentration in the blood causes hemic hypoxia through a decrease in its oxygen capacity. Hemic hypoxia stimulates 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, a redistribution of minute circulatory volume (MCV) occurs, aimed at maintaining a normal level of oxygen delivery to the brain, heart and lungs. In particular, the volumetric velocity of blood flow in the kidneys decreases.

Diabetes mellitus is primarily characterized by hyperglycemia, that is, pathologically high levels of glucose in the blood, and other metabolic disorders associated with pathologically low insulin secretion, the concentration of a normal hormone in the circulating blood, or representing a consequence of the insufficiency or absence of the 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 atherosclerosis of the arteries, as well as neuropathy at the level of peripheral somatic nerves, sympathetic and parasympathetic nerves conductors and ganglia.

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

If insulin-dependent diabetes mellitus results from 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.

The prolonged and extreme effect of inevitable stimuli as stress stimuli (postoperative period in conditions of ineffective analgesia, condition due to severe wounds and traumas, persistent negative psycho-emotional stress caused by unemployment and poverty, etc.) causes long-term and pathogenic activation of the sympathetic division of the autonomic nervous system. system and the neuroendocrine catabolic system. These changes 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 administration of insulin.

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 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 often in women than in men. In Hashimoto's disease, a uniform enlargement of the thyroid gland is barely noticeable, and autoantibodies to thyroglobulin autoantigens and the microsomal fraction of the gland circulate in the blood of patients.

Hashimoto's disease, as a cause of primary hypothyroidism, often develops simultaneously with an autoimmune lesion of the adrenal cortex, causing insufficient 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 TSH secretion, which causes hypothyroidism, it develops as a result of surgical interventions on the pituitary gland or is the result of its tumors. Secondary hypothyroidism is often combined with insufficient secretion of other hormones of the adenohypophysis, adrenocorticotropic and others.

The type of hypothyroidism (primary or secondary) can be determined by examining the levels of TSH and thyroxine (T4) in the blood serum. A low concentration of T4 with an increase in serum TSH levels 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 TSH secretion by the adenohypophysis. In this case, hypothyroidism is defined as primary. When serum TSH concentrations are reduced in hypothyroidism, or when, despite hypothyroidism, TSH concentrations are within the normal range, decreased thyroid function is secondary hypothyroidism.

With subtle subclinical hypothyroidism, that is, with minimal clinical manifestations or absence of symptoms of thyroid dysfunction, the T4 concentration may be within normal fluctuations. At the same time, the level of TSH in the serum is increased, which can presumably be associated with the reaction of increased secretion of TSH by the adenohypophysis in response to the action of thyroid hormones that is inadequate to the body’s needs. In such patients, from a pathogenetic point of view, it may be justified to prescribe thyroid drugs 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 athyroidism), hereditary disorders of the synthesis of its hormones associated with the lack of normal expression of genes for certain enzymes or its insufficiency, 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 one.

Hypothyroidism can be considered a pathological condition caused by a deficiency of free thyroid hormones in the circulating blood and throughout the body. It is known that the thyroid hormones triiodothyronine (T3) and thyroxine bind to nuclear receptors of target cells. The affinity of thyroid hormones for nuclear receptors is high. Moreover, the affinity for T3 is ten times higher than the affinity for T4.

The main effect of thyroid hormones on metabolism is an increase in oxygen consumption and free energy capture 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 the brain, cells of the mononuclear phagocyte system and gonads.

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

Systemic hypoergosis and a decrease in the excitability of the nerve centers due to hypothyroidism manifests itself with such characteristic symptoms of insufficient thyroid function as increased fatigue, drowsiness, as well as slowed speech and a decline in cognitive functions. Disturbances in intracentral relationships 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 caused by 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 increasing the efficiency of this mechanism of active transmembrane ion transport. This occurs through an increase in the capture of free energy by cells and through an increase in the number of units of the Na+/K+-ATPase pump.

Thyroid hormones increase the sensitivity of adrenergic receptors of the heart, blood vessels and other effector functions. 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 transmitter norepinephrine. Hypothyroidism, reducing the intensity of adrenergic stimulation of the effectors of the circulatory system, leads to a decrease in minute volume of blood circulation (MCV) and bradycardia under conditions of relative rest. Another reason for low values ​​of minute volume of blood circulation is a reduced level of oxygen consumption as a determinant of IOC. A decrease in adrenergic stimulation of the sweat glands manifests itself as a characteristic dry rut.

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

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

¦ Arterial hypotension as a consequence of a decrease in 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 caused by 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 gene transcription mechanism. This is the main mechanism through which the effect of T3 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 cause growth retardation. Thyroid hormones stimulate protein synthesis at the systemic level not only through increasing the expression of the somatotropin gene. They enhance protein synthesis, modulating the functioning of other elements of the genetic material of cells and increasing the permeability of the plasma membrane to amino acids. In this regard, hypothyroidism can be considered a pathological condition that characterizes the inhibition of protein synthesis as the cause of delayed mental development and body growth in children with hypothyroidism. The inability to rapidly intensify protein synthesis in immunocompetent cells associated with hypothyroidism may cause dysregulation of the specific immune response and acquired immunodeficiency due to dysfunction of both T and B cells.

One of the effects of thyroid hormones on metabolism is an increase in lipolysis and oxidation of fatty acids with a decrease in their levels in the circulating blood. 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. Body weight growth is often moderate, which is associated with anorexia (the result of a decrease in the excitability of the nervous system and the waste of free energy by the body) and a low level of protein synthesis in patients with hypothyroidism.

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

The pathological condition of the body due to pathogenic excessive secretion of thyroid hormones is called hyperthyroidism. Thyrotoxicosis refers to hyperthyroidism of extreme severity.

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