Blood its value composition and general properties. The main functions of blood and the composition of human blood

Blood is a liquid tissue of the body, constantly moving through the blood vessels, washing and moisturizing all the tissues and systems of the body. It makes up 6-8% of the total body weight (5 liters). Blood in the human body performs at least seven different functions, but they all have one thing in common - the transportation of gases and other substances. First, it carries oxygen from the lungs to the tissues, and carbon dioxide, formed in the process of metabolism, from the tissues to the lungs. Secondly, it transports all the nutrients from the digestive tract to the organs or to stores (into the "pads" of adipose tissue).

Blood also performs an excretory function, as it carries metabolic products to be removed to the organs of the excretory system. In addition, it is involved in maintaining the constancy of the composition of the fluids of various cells and organs, and also regulates the temperature of the human body. It delivers hormones - chemical "letters" from the endocrine glands to organs distant from them. Finally, blood plays an important role in the immune system, as it protects the body from invading pathogens and harmful substances.

Compound

Blood consists of plasma (about 55%) and formed elements (about 45%). Its viscosity is 4-5 times higher than water. Plasma contains 90% water, and the rest is proteins, fats, carbohydrates and minerals. There must be a certain amount of each of these substances in the blood. Liquid plasma carries various cells. The three main groups of these cells are erythrocytes (red blood cells), leukocytes (white blood cells), and platelets (platelets).

Most of all in the blood of erythrocytes, giving it a characteristic red color. In men, 1 mm cube. blood has 5 million red blood cells, while women have only 4.5 million. These cells ensure the circulation of oxygen and carbon dioxide between the lungs and other organs of the body. In this process, the red blood pigment, hemoglobin, becomes the "chemical vessel". Erythrocytes live for about 120 days. Therefore, in one second, about 2.4 million new cells should form in the bone marrow - this ensures a constant number of red blood cells circulating in the blood.

Leukocytes

In a healthy person, 1 mm cube. contains 4500-8000 leukocytes. After eating, their number can increase significantly. Leukocytes "recognize" and destroy pathogens and foreign substances. If the content of leukocytes has increased, then this may mean the presence of an infectious disease or inflammation. The third group of cells are small and rapidly decaying platelets. In 1 mm 3 of blood there are 0.15-0.3 million platelets, which play an important role in the process of its coagulation: platelets clog damaged vessels, preventing large blood loss.

general information

Blood cancer (leukemia) is an uncontrolled increase in the number of white blood cells. They are produced in pathologically altered cells of the bone marrow, therefore, they cease to perform their functions, which leads to a breakdown in human immunity.
Calcification of blood vessels leads to the rapid formation of blood clots, which can cause a heart attack, stroke, or pulmonary embolism if they block a blood vessel in one of these organs.
Approximately 5-6 liters of blood circulate in the body of an adult. If a person suddenly loses 1 liter of blood, for example, as a result of an accident, then there is nothing to worry about. Therefore, donation does no harm (0.5 liters of blood is taken from the donor).

Blood is the most complex liquid tissue of the body, the amount of which on average is up to seven percent of the total body weight of a person. In all vertebrates, this mobile fluid has a red tint. And in some species of arthropods, it is blue. This is due to the presence of hemocyanin in the blood. All about the structure of human blood, as well as such pathologies as leukocytosis and leukopenia - to your attention in this material.

The composition of human blood plasma and its functions

Speaking about the composition and structure of blood, one should start with the fact that blood is a mixture of various solid particles floating in a liquid. Solid particles are blood cells that make up about 45% of the volume of blood: red (they are the majority and they give blood its color), white and platelets. The liquid part of the blood is plasma: it is colorless, consists mainly of water and carries nutrients.

Plasma human blood is the intercellular fluid of blood as tissue. It consists of water (90-92%) and dry residue (8-10%), which, in turn, form both organic and inorganic substances. All vitamins, microelements, metabolic intermediates (lactic and pyruvic acids) are constantly present in the plasma.

Organic substances of blood plasma: what part are proteins

Organic substances include proteins and other compounds. Plasma proteins make up 7-8% of the total mass, they are divided into albumins, globulins and fibrinogen.

The main functions of blood plasma proteins:

colloid osmotic (protein) and water homeostasis;
ensuring the correct aggregate state of blood (liquid);
acid-base homeostasis, maintaining a constant level of acidity pH (7.34-7.43);
immune homeostasis;
another important function of blood plasma is transport (transfer of various substances);
nutritious;
involved in blood clotting.

Albumins, globulins and fibrinogen in blood plasma

Albumins, which largely determine the composition and properties of blood, are synthesized in the liver and make up about 60% of all plasma proteins. They retain water inside the lumen of blood vessels, serve as a reserve of amino acids for protein synthesis, and also carry cholesterol, fatty acids, bilirubin, bile salts and heavy metals, and drugs. With a lack of albumin in the biochemical composition of the blood, for example, due to renal failure, the plasma loses its ability to retain water inside the vessels: the fluid enters the tissues, and edema develops.

Blood globulins are formed in the liver, bone marrow, and spleen. These blood plasma substances are divided into several fractions: α-, β- and γ-globulins.

to α-globulins , which transport hormones, vitamins, microelements and lipids, include erythropoietin, plasminogen and prothrombin.

Kβ-globulins , which are involved in the transport of phospholipids, cholesterol, steroid hormones and metal cations, include the protein transferrin, which provides iron transport, as well as many blood coagulation factors.

The basis of immunity is γ-globulins. Being part of human blood, they include various antibodies, or immunoglobulins, of 5 classes: A, G, M, D and E, which protect the body from viruses and bacteria. This fraction also includes α - and β - blood agglutinins, which determine its group affiliation.

fibrinogen blood is the first coagulation factor. Under the influence of thrombin, it passes into an insoluble form (fibrin), providing the formation of a blood clot. Fibrinogen is produced in the liver. Its content increases sharply with inflammation, bleeding, trauma.

The organic substances of blood plasma also include non-protein nitrogen-containing compounds (amino acids, polypeptides, urea, uric acid, creatinine, ammonia). The total amount of the so-called residual (non-protein) nitrogen in the blood plasma is 11-15 mmol / l (30-40 mg%). Its content in the blood system increases sharply in case of impaired renal function, therefore, in case of renal failure, the consumption of protein foods is limited.

In addition, the composition of blood plasma includes nitrogen-free organic substances: glucose 4.46.6 mmol / l (80-120 mg%), neutral fats, lipids, enzymes, fats and proteins, proenzymes and enzymes involved in blood coagulation processes.

Inorganic substances in the composition of blood plasma, their features and effects

Speaking about the structure and functions of the blood, we must not forget about the minerals that make up it. These inorganic compounds of blood plasma make up 0.9-1%. These include salts of sodium, calcium, magnesium, chlorine, phosphorus, iodine, zinc and others. Their concentration is close to the concentration of salts in sea water: after all, it was there that the first multicellular creatures first appeared millions of years ago. Plasma minerals are jointly involved in the regulation of osmotic pressure, blood pH, and a number of other processes. For example, the main effect of calcium ions in the blood is on the colloidal state of the contents of the cells. They are also involved in the process of blood clotting, regulation of muscle contraction and sensitivity of nerve cells. Most of the salts in human blood plasma are associated with proteins or other organic compounds.

In some cases, there is a need for plasma transfusion: for example, with kidney disease, when the albumin content in the blood decreases sharply, or with extensive burns, since a lot of tissue fluid containing proteins is lost through the burn surface. There is an extensive practice of collecting donated blood plasma.

Formed elements in blood plasma

Shaped elements is the general name for blood cells. The formed elements of blood include erythrocytes, leukocytes and platelets. Each of these classes of cells in the composition of human blood plasma, in turn, is divided into subclasses.

Since untreated cells that are examined under a microscope are practically transparent and colorless, a blood sample is applied to a laboratory glass and stained with special dyes.

Cells vary in size, shape, nucleus shape, and ability to bind dyes. All these signs of cells that determine the composition and characteristics of blood are called morphological.

Red blood cells in human blood: shape and composition

Erythrocytes in the blood (from Greek erythros - "red" and kytos - "receptacle", "cage") Red blood cells are the most numerous class of blood cells.

The human erythrocyte population is heterogeneous in shape and size. Normally, the bulk of them (80-90%) are discocytes (normocytes) - erythrocytes in the form of a biconcave disc with a diameter of 7.5 microns, a thickness of 2.5 microns on the periphery, and 1.5 microns in the center. An increase in the diffusion surface of the membrane contributes to the optimal performance of the main function of erythrocytes - oxygen transport. The specific form of these elements of the blood composition also ensures their passage through narrow capillaries. Since the nucleus is absent, erythrocytes do not need much oxygen for their own needs, which allows them to fully supply oxygen to the entire body.

In addition to discocytes, planocytes (cells with a flat surface) and aging forms of erythrocytes are also distinguished in the structure of human blood: styloid, or echinocytes (~ 6%); domed, or stomatocytes (~ 1-3%); spherical, or spherocytes (~ 1%).

The structure and functions of erythrocytes in the human body

The structure of a human erythrocyte is such that they are devoid of a nucleus and consist of a frame filled with hemoglobin and a protein-lipid membrane - a membrane.

The main functions of erythrocytes in the blood:

transport (gas exchange): the transfer of oxygen from the alveoli of the lungs to the tissues and carbon dioxide in the opposite direction;
another function of red blood cells in the body is the regulation of blood pH (acidity);
nutritional: the transfer on its surface of amino acids from the digestive organs to the cells of the body;
protective: adsorption of toxic substances on its surface;
due to its structure, the function of erythrocytes is also participation in the process of blood coagulation;
are carriers of various enzymes and vitamins (B1, B2, B6, ascorbic acid);
carry signs of a certain blood group hemoglobin and its compounds.

The structure of the blood system: types of hemoglobin

The filling of red blood cells is hemoglobin - a special protein, thanks to which red blood cells perform the function of gas exchange and maintain blood pH. Normally, in men, each liter of blood contains an average of 130-160 g of hemoglobin, and in women - 120-150 g.

Hemoglobin consists of a globin protein and a non-protein part - four heme molecules, each of which includes an iron atom that can attach or donate an oxygen molecule.

When hemoglobin is combined with oxygen, oxyhemoglobin is obtained - a fragile compound in the form of which most of the oxygen is transferred. Hemoglobin that has given up oxygen is called reduced hemoglobin, or deoxyhemoglobin. Hemoglobin combined with carbon dioxide is called carbohemoglobin. In the form of this compound, which also readily decomposes, 20% of carbon dioxide is transported.

Skeletal and cardiac muscles contain myoglobin - muscle hemoglobin, which plays an important role in supplying working muscles with oxygen.

There are several types and compounds of hemoglobin, differing in the structure of its protein part - globin. For example, fetal blood contains hemoglobin F, while hemoglobin A predominates in adult erythrocytes.

Differences in the protein part of the structure of the blood system determine the affinity of hemoglobin for oxygen. In hemoglobin F, it is much larger, which helps the fetus not experience hypoxia with a relatively low oxygen content in its blood.

In medicine, it is customary to calculate the degree of saturation of red blood cells with hemoglobin. This is the so-called color index, which is normally equal to 1 (normochromic erythrocytes). Determining it is important for diagnosing various types of anemia. So, hypochromic erythrocytes (less than 0.85) indicate iron deficiency anemia, and hyperchromic (more than 1.1) indicate a lack of vitamin B12 or folic acid.

Erythropoiesis - what is it?

Erythropoiesis- This is the process of formation of red blood cells, occurs in the red bone marrow. Erythrocytes together with hematopoietic tissue are called red blood germ, or erythron.

For The formation of red blood cells requires, first of all, iron and certain .

Both from the hemoglobin of decomposing erythrocytes and from food: having been absorbed, it is transported by plasma to the bone marrow, where it is included in the hemoglobin molecule. Excess iron is stored in the liver. With a lack of this essential trace element, iron deficiency anemia develops.

The formation of red blood cells requires vitamin B12 (cyanocobalamin) and folic acid, which are involved in DNA synthesis in young forms of red blood cells. Vitamin B2 (riboflavin) is necessary for the formation of the skeleton of red blood cells. (pyridoxine) takes part in the formation of heme. Vitamin C (ascorbic acid) stimulates the absorption of iron from the intestines, enhances the action of folic acid. (alpha-tocopherol) and PP (pantothenic acid) strengthen the erythrocyte membrane, protecting them from destruction.

Other trace elements are also necessary for normal erythropoiesis. So, copper helps the absorption of iron in the intestine, and nickel and cobalt are involved in the synthesis of red blood cells. Interestingly, 75% of all zinc found in the human body is found in red blood cells. (Lack of zinc also causes a decrease in the number of leukocytes.) Selenium, interacting with vitamin E, protects the erythrocyte membrane from damage by free radicals (radiation).

How is erythropoiesis regulated and what stimulates it?

The regulation of erythropoiesis occurs due to the hormone erythropoietin, which is formed mainly in the kidneys, as well as in the liver, spleen, and in small amounts constantly present in the blood plasma of healthy people. It enhances the production of red blood cells and accelerates the synthesis of hemoglobin. In severe kidney disease, erythropoietin production decreases and anemia develops.

Erythropoiesis is stimulated by male sex hormones, which leads to a higher content of red blood cells in men than in women. Inhibition of erythropoiesis is caused by special substances - female sex hormones (estrogens), as well as inhibitors of erythropoiesis, which are formed when the mass of circulating red blood cells increases, for example, when descending from the mountains to the plain.

The intensity of erythropoiesis is judged by the number of reticulocytes - immature erythrocytes, the number of which is normally 1-2%. Mature erythrocytes circulate in the blood for 100-120 days. Their destruction occurs in the liver, spleen and bone marrow. The breakdown products of erythrocytes are also hematopoietic stimulants.

Erythrocytosis and its types

Normally, the content of red blood cells in the blood is 4.0-5.0x10-12 / l (4,000,000-5,000,000 in 1 μl) in men, and 4.5x10-12 / l (4,500,000 in 1 µl). An increase in the number of red blood cells in the blood is called erythrocytosis, and a decrease is called anemia (anemia). With anemia, both the number of red blood cells and the content of hemoglobin in them can be reduced.

Depending on the cause of occurrence, 2 types of erythrocytosis are distinguished:

Compensatory- arise as a result of the body's attempt to adapt to a lack of oxygen in any situation: during long-term residence in highlands, among professional athletes, with bronchial asthma, hypertension.
True polycythemia- a disease in which, due to a violation of the bone marrow, the production of red blood cells increases.

Types and composition of leukocytes in the blood

Leukocytes (from the Greek Leukos - "white" and kytos - "receptacle", "cage") called white blood cells - colorless blood cells ranging in size from 8 to 20 microns. The composition of leukocytes includes the nucleus and cytoplasm.

There are two main types of blood leukocytes: depending on whether the cytoplasm of leukocytes is homogeneous or contains granularity, they are divided into granular (granulocytes) and non-granular (agranulocytes).

Granulocytes are of three types: basophils (stain blue and blue with alkaline dyes), eosinophils (stain pink with acidic dyes), and neutrophils (stain with both alkaline and acidic dyes; this is the most numerous group). Neutrophils according to the degree of maturity are divided into young, stab and segmented.

Agranulocytes, in turn, are of two types: lymphocytes and monocytes.

Details about each type of leukocytes and their functions are in the next section of the article.

What is the function of all types of leukocytes in the blood

The main functions of leukocytes in the blood are protective, but each type of leukocyte performs its function in different ways.

The main function of neutrophils- phagocytosis of bacteria and tissue decay products. The process of phagocytosis (active capture and absorption of living and non-living particles by phagocytes - special cells of multicellular animal organisms) is extremely important for immunity. Phagocytosis is the first step in wound healing (cleaning). That is why in people with a reduced number of neutrophils, wounds heal slowly. Neutrophils produce interferon, which has an antiviral effect, and secrete arachidonic acid, which plays an important role in regulating the permeability of blood vessels and in triggering processes such as inflammation, pain, and blood clotting.

Eosinophils neutralize and destroy toxins of foreign proteins (for example, bee, wasp, snake venom). They produce histaminase, an enzyme that destroys histamine, which is released during various allergic conditions, bronchial asthma, helminthic invasions, and autoimmune diseases. That is why in these diseases the number of eosinophils in the blood increases. Also, this type of leukocyte performs such a function as the synthesis of plasminogen, which reduces blood clotting.

Basophils produce and contain the most important biologically active substances. So, heparin prevents blood clotting in the focus of inflammation, and histamine expands the capillaries, which contributes to its resorption and healing. Basophils also contain hyaluronic acid, which affects the permeability of the vascular wall; platelet activating factor (PAF); thromboxanes that promote aggregation (clumping) of platelets; leukotrienes and prostaglandin hormones.

In allergic reactions, basophils release biologically active substances into the blood, including histamine. Itching in places of mosquito and midge bites appears due to the work of basophils.

Monocytes are produced in the bone marrow. They are in the blood for no more than 2-3 days, and then they go into the surrounding tissues, where they reach maturity, turning into tissue macrophages (large cells).

Lymphocytes- the main actor of the immune system. They form specific immunity (protection of the body from various infectious diseases): they perform the synthesis of protective antibodies, lysis (dissolution) of foreign cells, and provide immune memory. Lymphocytes are formed in the bone marrow, and specialization (differentiation) takes place in the tissues.

There are 2 classes of lymphocytes: T-lymphocytes (mature in the thymus gland) and B-lymphocytes (mature in the intestine, palatine and pharyngeal tonsils).

Depending on the functions performed, they differ:

T-killers (the killers), dissolving foreign cells, pathogens of infectious diseases, tumor cells, mutant cells;

T-helpers(assistant) interacting with B-lymphocytes;

T-suppressors (oppressors) blocking excessive reactions of B-lymphocytes.

The memory cells of T-lymphocytes store information about contacts with antigens (foreign proteins): this is a kind of database where all infections that our body has encountered at least once are entered.

Most B-lymphocytes produce antibodies - proteins of the immunoglobulin class. In response to the action of antigens (foreign proteins), B-lymphocytes interact with T-lymphocytes and monocytes and turn into plasma cells. These cells synthesize antibodies that recognize and bind the appropriate antigens in order to destroy them. Among B-lymphocytes there are also killers, helpers, suppressors and immunological memory cells.

Leukocytosis and leukopenia of the blood

The number of leukocytes in the peripheral blood of an adult normally ranges from 4.0-9.0x109 / l (4000-9000 in 1 μl). Their increase is called leukocytosis, and their decrease is called leukopenia.

Leukocytosis can be physiological (food, muscle, emotional, and also occurring during pregnancy) and pathological. With pathological (reactive) leukocytosis, cells are ejected from the hematopoietic organs with a predominance of young forms. The most severe leukocytosis occurs with leukemia: leukocytes are not able to perform their physiological functions, in particular, to protect the body from pathogenic bacteria.

Leukopenias are observed when exposed to radiation (especially as a result of damage to the bone marrow during radiation sickness) and X-rays, with some serious infectious diseases (sepsis, tuberculosis), and also due to the use of a number of drugs. With leukopenia, there is a sharp inhibition of the body's defenses in the fight against a bacterial infection.

When studying a blood test, not only the total number of leukocytes is important, but also the percentage of their individual types, called the leukocyte formula, or leukogram. An increase in the number of young and stab neutrophils is called a shift of the leukocyte formula to the left: it indicates an accelerated renewal of the blood and is observed in acute infectious and inflammatory diseases, as well as in leukemia. In addition, a shift in the leukocyte formula may occur during pregnancy, especially in the later stages.

What is the function of platelets in the blood

Platelets (from the Greek trombos - "lump", "clot" and kytos - "receptacle", "cell") called platelets - flat cells of irregular round shape with a diameter of 2-5 microns. In humans, they do not have nuclei.

Platelets are formed in the red bone marrow from giant cells of megakaryocytes. Platelets live from 4 to 10 days, after which they are destroyed in the liver and spleen.

The main functions of platelets in the blood:

Prevention of large vessels when injured, as well as healing and regeneration of damaged tissues. (Platelets can adhere to a foreign surface or stick together.)
Platelets also perform such a function as the synthesis and release of biologically active substances (serotonin, adrenaline, norepinephrine), and also help in blood clotting.
Phagocytosis of foreign bodies and viruses.
Platelets contain a large amount of serotonin and histamine, which affect the size of the lumen and the permeability of blood capillaries.

Dysfunction of platelets in the blood

The number of platelets in the peripheral blood of an adult is normally 180-320x109 / l, or 180,000-320,000 per 1 μl. There are diurnal fluctuations: there are more platelets during the day than at night. A decrease in the number of platelets is called thrombocytopenia, and an increase is called thrombocytosis.

Thrombocytopenia occurs in two cases: when insufficient numbers of platelets are produced in the bone marrow or when they are rapidly destroyed. Radiation, taking a number of medications, a deficiency of certain vitamins (B12, folic acid), alcohol abuse and, in particular, serious diseases such as viral hepatitis B and C, cirrhosis of the liver, HIV and malignant tumors can negatively affect the production of platelets. Increased destruction of platelets most often develops when the immune system fails, when the body begins to produce antibodies not against microbes, but against its own cells.

With a platelet disorder such as thrombocytopenia, there is a tendency to bruising (bruising) easily with little or no cause at all; bleeding with minor injuries and operations (tooth extraction); in women - profuse blood loss during menstruation. If you notice at least one of these symptoms, you should consult a doctor and perform a blood test.

With thrombocytosis, the opposite picture is observed: due to an increase in the number of platelets, blood clots appear - blood clots that clog blood flow through the vessels. This is very dangerous because it can lead to myocardial infarction, stroke and thrombophlebitis of the extremities, more often the lower ones.

In some cases, platelets, despite the fact that their number is normal, cannot fully perform their functions (usually due to a membrane defect), and increased bleeding is observed. Such disorders of platelet function can be both congenital and acquired (including those developed under the influence of long-term medication: for example, with frequent uncontrolled intake of painkillers, which include analgin).

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

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

Composition of blood: blood cells

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

erythrocytes (red blood cells);
leukocytes (white blood cells);
platelets (platelets).

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

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

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

Blood composition: normal

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

The chemical composition of human blood

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

Eating before a blood test to increase the concentration of fat.
Fasting for 2 days will increase bilirubin in the blood.
Fasting more than 4 days will reduce the amount of urea and fatty acids.
Fatty foods will increase your potassium and triglyceride levels.
Eating too much meat will increase your urate levels.
Coffee increase the level of glucose, fatty acids, leukocytes and erythrocytes.

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

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 erythrocytes. In the arteries, through which the blood that has entered the heart from the lungs is transferred to the tissues of the body, hemoglobin is saturated with oxygen and is colored bright red; in the veins, through which blood flows from the tissues to the heart, hemoglobin is practically devoid of oxygen and 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 largely determines the rate at which blood flows through the arteries (semi-elastic structures) and blood pressure. The fluidity of blood is also determined by its density and the nature of the movement of various types of cells. Leukocytes, for example, move singly, in close proximity to the walls of blood vessels; erythrocytes can move both individually and in groups, like stacked coins, creating an axial, i.e. concentrated in the center of the vessel, flow. The blood volume of an adult male 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 male 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 just the transport of nutrients and waste products of metabolism. Blood also carries hormones that control many vital processes; 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 functions of the body, without which life is impossible, are closely related to blood and blood supply. The connection with respiration is expressed in the fact that the blood provides gas exchange in the lungs and transport of the corresponding gases: oxygen - from the lungs to the tissues, carbon dioxide (carbon dioxide) - from the tissues to the lungs. The transport of nutrients begins from the capillaries of the small intestine; here, the blood captures them from the digestive tract and transfers them to all organs and tissues, starting with the liver, where nutrients (glucose, amino acids, fatty acids) are modified, and the liver cells regulate their level in the blood depending on the needs of the body (tissue metabolism) . The transition of transported substances from the blood into tissues is carried out 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). Blood also carries the products of secretion of the endocrine glands - hormones - and thus provides 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 various 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 skin blood vessels in 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 an infection, certain waste products of microorganisms or the products of tissue breakdown caused by them interact with leukocytes, causing the formation of chemicals that stimulate the temperature regulation center in the brain. As a result, there is a rise in body temperature, felt as heat.

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

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

Leukocytes are also involved 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 belongs to 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 are present on cells foreign to the given organism). It may take several weeks for lymphocytes to develop antibodies against an antigen that the body encounters for the first time, but the resulting immunity lasts for 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 rapidly. This phenomenon is called immunological memory. P

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

blood pH. pH is a measure 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 the carbon dioxide dissolved in it: carbon dioxide (CO2), which is formed during metabolic processes, reacts with water (H2O) when dissolved in the blood, forming carbonic acid (H2CO3).

Maintaining the pH of the blood at a constant level, i.e., in other words, the 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. A change in blood pH that goes beyond the range of 6.8-7.7 is incompatible with life. The maintenance of this indicator at a constant level is facilitated, in particular, by the kidneys, 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 (ie, the ability to neutralize some excess acid or alkali).

Physico-chemical properties of blood. The density of whole blood depends mainly on the content of erythrocytes, proteins and lipids in it. The color of the 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 colloid-polymer solution in which water is a solvent, salts and low-molecular organic plasma islands are dissolved substances, and proteins and their complexes are a 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 electrical double layer, an electrokinetic potential arises, which plays an important role in stabilizing cells, preventing their aggregation. With an increase in the ionic strength of the plasma due to the ingress of multiply charged positive ions into it, the diffuse layer shrinks and the barrier that prevents 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 clotting 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 a change in the protein composition of the plasma. The sedimentation of erythrocytes is preceded by their aggregation with the formation of certain structures such as coin columns. ESR depends on how they are formed. The concentration of plasma hydrogen ions is expressed in terms of the hydrogen index, i.e. negative logarithm of the activity of hydrogen ions. The average blood pH is 7.4. Maintenance of a constancy of this size big fiziol. value, since it determines the speed of so many chem. and fiz.-chem. processes in the body.

Normally, the pH of arterial K. 7.35-7.47 of venous blood is 0.02 lower, the content of erythrocytes usually has a 0.1-0.2 more acidic reaction 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 the flow conditions. In this regard, the viscosity of blood in large vessels and capillaries varies significantly, and the data on viscosity given in the literature are conditional. The patterns of blood flow (blood rheology) are not well understood. The non-Newtonian behavior of blood is explained by the high volumetric 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 a few tenths of a millimeter), the viscosity of blood is 4-5 times higher than the viscosity of water.

With pathology and injuries, 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 blood the properties of a 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 in case of imbalance in the coagulation system is one of the causes of thrombosis. The formation of a fibrin clot is prevented by the anticoagulant system of blood; 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 the clot is retracted.

Blood components

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

Thus, the plasma contacts 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 given in the table. Among the substances dissolved in the 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) are sodium (Na+), potassium (K+), calcium (Ca2+) and magnesium (Mg2+) cations; 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, which ensures the normal distribution of fluid between the blood vessels and the extravascular space. With starvation or insufficient intake of proteins from food, the content of albumin in plasma falls, which can lead to increased accumulation of water in the tissues (edema). This condition associated with protein deficiency is called starvation edema. There are several types or classes of globulins in plasma, the most important of which are denoted 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 found only in fractions g1, g2 and b. Although antibodies are often referred to as gamma globulins, the fact that some of them are also present in the b-fraction led to the introduction of the term "immunoglobulin". The a- and b-fractions contain many different proteins that ensure the transport of iron, vitamin B12, steroids and other hormones in the blood. This group of proteins also includes coagulation factors, which, along with fibrinogen, are involved in the process of blood coagulation. The main function of fibrinogen is to form blood clots (thrombi). In the process of blood clotting, whether in vivo (in a living organism) or in vitro (outside the body), fibrinogen is converted to fibrin, which forms the basis of a blood clot; fibrinogen-free plasma, usually a clear, pale yellow liquid, is called blood serum.

red blood cells. Red blood cells, or erythrocytes, are round disks 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 erythrocytes. They make up 44-48% of the total blood volume. Erythrocytes have the shape of a biconcave disc, i.e. the flat sides of the disc are sort of compressed, making it look like a donut without a hole. Mature erythrocytes do not have nuclei. They contain mainly hemoglobin, the concentration of which in the intracellular aqueous medium 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, erythrocytes contain dissolved inorganic ions (mainly K +) and various enzymes. The two concave sides provide the erythrocyte with an optimal surface area through which the exchange of gases, carbon dioxide and oxygen, can take place.

Thus, the shape of cells largely determines the efficiency of physiological processes. In humans, the surface area through which gas exchange takes place averages 3820 m2, which is 2000 times the surface of the body. In the fetus, primitive red blood cells are first formed in the liver, spleen, and thymus. From the fifth month of intrauterine development, erythropoiesis gradually begins in the bone marrow - the formation of full-fledged red blood cells. In exceptional circumstances (for example, when normal bone marrow is replaced by cancerous tissue), the adult body can again switch to the formation of 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).

Erythrocytes develop from precursor cells, the source of which is the so-called. stem cells. In the early stages of erythrocyte formation (in cells still in the bone marrow), the cell nucleus is clearly identified. As the cell matures, hemoglobin accumulates, which is 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, erythrocytes are formed faster than normal, and in this case, immature forms containing a nucleus can enter the bloodstream; apparently this is due to the fact that the cells leave the bone marrow too quickly.

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

Hemoglobin. The main function of the erythrocyte 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 compound of porphyrin 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 normal aqueous solution.

The degree of oxygen binding 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 plasma environment and enters the red blood cells; where it binds to hemoglobin to form oxyhemoglobin. In tissues where the oxygen concentration is low, oxygen molecules are separated from hemoglobin and penetrate into tissues by diffusion. Insufficiency of erythrocytes or hemoglobin leads to a decrease in oxygen transport and thus to a violation of biological processes in tissues. In humans, fetal hemoglobin (type F, from fetus - fetus) and adult hemoglobin (type A, from adult - adult) are distinguished. Many genetic variants of hemoglobin are known, the formation of which leads to abnormalities of red blood cells or their function. Among them, hemoglobin S is the most well-known, causing sickle cell anemia.

Leukocytes. White cells of peripheral blood, 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 nuclei are predominantly regular round in shape. Cells with specific granules (granulocytes) are characterized, as a rule, by the presence of irregularly shaped nuclei with many lobes and are therefore called polymorphonuclear leukocytes. They are divided into three varieties: neutrophils, basophils and eosinophils. They differ from each other in the pattern of staining of granules with different dyes. In a healthy person, 1 mm3 of blood contains from 4,000 to 10,000 leukocytes (about 6,000 on average), which is 0.5-1% of the blood volume. The ratio of individual types of cells in the composition of leukocytes can vary significantly in different people and even in the same person at different times.

Polymorphonuclear leukocytes(neutrophils, eosinophils and basophils) are formed in the bone marrow from progenitor cells that originate from stem cells, probably the same ones that give rise to erythrocyte precursors. As the nucleus matures, granules appear in the cells, typical for each type of cell. In the bloodstream, these cells move along the walls of the capillaries primarily due to amoeboid movements. Neutrophils are able to leave the interior of the vessel and accumulate at the site of infection. The life span 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 stain their core purple; the nucleus of peripheral blood neutrophils can have from one to five lobes. The cytoplasm stains 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 determination in the study of blood samples. Eosinophils are similar in size to neutrophils. Their nucleus rarely has more than three lobes, and the cytoplasm contains many large granules that are clearly stained bright red with eosin dye. Unlike eosinophils in basophils, cytoplasmic granules are 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. The cytoplasm is bluish-gray when stained, contains a small number of inclusions, stained with azure dye in a blue-violet color. Monocytes are produced 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 are less than 10 µm in diameter, but lymphocytes with a larger diameter (16 µm) are occasionally found. Cell nuclei are dense and round, the cytoplasm is bluish in color, with very rare granules. Despite the fact that lymphocytes look morphologically homogeneous, they clearly differ in their functions and properties of the cell membrane. 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, after which they migrate to the lymphoid organs. They serve as precursors to cells that form antibodies, the so-called. plasma. In order for B cells to transform into plasma cells, the presence of T cells is required. 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 sternum. There they differentiate into T-lymphocytes, a highly heterogeneous population of immune system cells with different functions. Thus, they synthesize macrophage activating factors, B-cell growth factors and interferons. Among T cells, there are inductor (helper) cells that stimulate the production 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", ie. kill cancer cells and cells infected with the virus. However, in general, the role of 0-cells is unclear.

platelets are colorless, nuclear-free bodies of spherical, oval or rod-shaped shape with a diameter of 2-4 microns. Normally, the content of platelets in peripheral blood is 200,000-400,000 per 1 mm3. Their life expectancy is 8-10 days. With standard dyes (azure-eosin), they are stained in a uniform pale pink color. Using electron microscopy, it was shown that platelets are similar to ordinary cells in the structure of the cytoplasm; however, in fact, they are not cells, but fragments of the cytoplasm of very large cells (megakaryocytes) present in the bone marrow. Megakaryocytes are descended from the same stem cells that give rise to erythrocytes and leukocytes. As will be shown in the next section, platelets play a key role in blood clotting. Damage to the bone marrow from drugs, ionizing radiation, or cancer can lead to a significant decrease in the number of platelets in the blood, which causes spontaneous hematomas and bleeding.

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

Hemostasis (stop bleeding). When a thin or even medium blood vessel is damaged, for example, when tissue is cut or squeezed, 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 vessel lumen contracts in response to released chemicals and nerve impulses. When the endothelial lining of the blood vessels is damaged, the collagen underlying the endothelium is exposed, on which platelets circulating in the blood quickly adhere. They release chemicals that cause vasoconstriction (vasoconstrictors). Platelets also secrete other substances that are involved 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 capture blood cells. One of the most important properties of fibrin is its ability to polymerize to form long fibers that contract and push the blood serum out of the clot.

Thrombosis- abnormal blood clotting in the arteries or veins. As a result of arterial thrombosis, the blood supply to the tissues worsens, which causes their damage. This occurs with myocardial infarction caused by thrombosis of the coronary artery, or with a stroke caused by thrombosis of cerebral vessels. Venous thrombosis prevents the normal outflow of blood from the tissues. When a large vein is blocked by a thrombus, edema occurs near the blockage site, 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 a life-threatening circulatory disorder.

Several factors predisposing to intravascular thrombosis have been identified; These include:

slowing of venous blood flow due to low physical activity;
vascular changes caused by increased blood pressure;
local compaction of the inner surface of blood vessels due to inflammatory processes or - in the case of arteries - due to the so-called. atheromatosis (deposits of lipids on the walls of arteries);
increased blood viscosity due to polycythemia (increased levels of red blood cells in the blood);
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 influence that causes damage to platelets can accelerate this process. When damaged, the surface of platelets becomes more sticky, which leads to their connection with each other (aggregation) and the release of their contents. The endothelial lining of blood vessels contains the so-called. prostacyclin, which inhibits the release of a thrombogenic substance, thromboxane A2, from platelets. Other plasma components also play an important role, preventing thrombosis in the 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 treatment with anticoagulants; It is recommended to start walking as soon as possible after surgery. It should be noted that even a small dose of aspirin daily (300 mg) reduces platelet aggregation and significantly reduces the likelihood of thrombosis.

Blood transfusion Since the late 1930s, the 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 trauma, during surgery, or during childbirth. Blood transfusion is 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 reputable physicians is that blood transfusion should be performed only in case of strict necessity, since it is associated with the risk of complications and the 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, qualified specialists are engaged in typing. A small amount of erythrocytes is added to an antiserum containing a large amount of antibodies to certain erythrocyte antigens. Antiserum is obtained from the blood of donors specially immunized with the appropriate blood antigens. Agglutination of erythrocytes 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 the blood groups of the AB0 system. As an additional in vitro test, you can mix the donor's erythrocytes with the recipient's serum, and vice versa, the donor's serum with the recipient's erythrocytes - and see if there is any agglutination. This test is called cross-typing. If at least a small number of cells agglutinate when mixing the donor's erythrocytes and the recipient's serum, the blood is considered incompatible.

Blood transfusion and storage. The original methods of direct blood transfusion from a donor to a recipient are a thing of the past. Today, donated blood is taken from a vein under sterile conditions into specially prepared containers, where an anticoagulant and glucose are previously added (the latter is used as a nutrient medium for erythrocytes during storage). Of the anticoagulants, sodium citrate is most often used, 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 original number of viable erythrocytes remains. Since this level of live red blood cells is considered the minimum acceptable, blood that has been stored for more than three weeks is not used for transfusion. Due to the growing need for blood transfusion, methods have emerged to preserve the viability of red blood cells for a longer time. In the presence of glycerol and other substances, erythrocytes can be stored for an arbitrarily long time at a temperature from -20 to -197 ° C. For storage at -197 ° C, metal containers with liquid nitrogen are used, into which containers with blood are immersed. Frozen blood is successfully used for transfusion. Freezing allows not only to create stocks of ordinary blood, but also to collect and store rare blood groups in special blood banks (repositories).

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

Today they are already talking about component therapy, when transfusion means the replacement of only those blood elements that the recipient needs. Most anemic people need only whole red blood cells; patients with leukemia require mainly platelets; Patients with hemophilia need only certain components of plasma. All of these fractions can be isolated from the same donated blood, leaving only albumin and gamma globulin (both have their uses). 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 the stations, as a rule, they only collect donated blood, and store it in blood banks (storages). The latter provide the blood of the required group at the request of hospitals and clinics. In addition, they usually have a special service that collects both plasma and individual fractions (for example, gamma globulin) from expired whole blood. Many banks also have qualified specialists who perform complete blood typing and study possible incompatibility reactions.

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Ministry of Education and Science of the Russian Federation

Tyumen State University

Institute of Biology

Composition and functions of blood

Tyumen 2015

Introduction

Blood is a red liquid, slightly alkaline reaction, salty taste with a specific gravity of 1.054-1.066. The total amount of blood in an adult averages about 5 liters (equal to 1/13 of body weight by weight). Together with tissue fluid and lymph, it forms the internal environment of the body. Blood performs a variety of functions. The most important of them are the following:

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

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

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

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

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

Blood clotting that prevents blood loss;

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

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

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

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

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

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

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

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

blood plasma hemoglobin anemia

1. Chemical composition of blood

Composition of blood: blood cells

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

erythrocytes (red blood cells);

leukocytes (white blood cells);

platelets (platelets).

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

Blood composition: normal

The chemical composition of human blood

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

Fasting for 2 days will increase bilirubin in the blood.

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

Fatty foods will increase your potassium and triglyceride levels.

Eating too much meat will increase your urate levels.

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

2. Blood plasma

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

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

Plasma composition

Plasma contains:

organic substances - blood proteins: albumins, globulins and fibrinogen

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

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

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

Blood proteins: albumin

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

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

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

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

Immunoglobulins

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

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

Other plasma proteins

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

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

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

Other plasma substances

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

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

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

3. Formed elements of blood

blood cells

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

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

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

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

Functions of red blood cells

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

red blood cells

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

Hemoglobin

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

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

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

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

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

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

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

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

Formation, destruction and pathology of erythrocytes

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

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

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

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

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

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

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

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

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

Erythrocyte sedimentation rate (ESR)

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

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

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

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

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

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

Neutrophils

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

Eosinophils

Basophils

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

Monocytes

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

Lymphocytes

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

...

Blood its value composition and general properties. The main functions of blood and the composition of human blood

Compound

Leukocytes

general information

The composition of human blood plasma and its functions

Albumins, globulins and fibrinogen in blood plasma

Inorganic substances in the composition of blood plasma, their features and effects

Formed elements in blood plasma

Red blood cells in human blood: shape and composition

The structure and functions of erythrocytes in the human body

The structure of the blood system: types of hemoglobin

Erythropoiesis - what is it?

How is erythropoiesis regulated and what stimulates it?

Erythrocytosis and its types

Types and composition of leukocytes in the blood

What is the function of all types of leukocytes in the blood

Leukocytosis and leukopenia of the blood

What is the function of platelets in the blood

Dysfunction of platelets in the blood

Composition of blood: blood cells

Blood composition: normal

The chemical composition of human blood

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