Why does a person need blood and what components does it consist of? The main components of human blood Composition and functions of human blood

The human body is extremely complex. Its elementary building particle is the cell. The union of cells that are similar in their structure and functions form a certain type of tissue. In total, there are four types of tissues in the human body: epithelial, nervous, muscle and connective. It is the latter type that blood belongs to. Below in the article we will discuss what it consists of.

General concepts

Blood is a liquid connective tissue that constantly circulates from the heart to all remote parts of the human body and carries out vital functions.

In all vertebrate organisms, it has a red color (of varying degrees of color intensity), acquired due to the presence of hemoglobin, a specific protein responsible for the transfer of oxygen. The role of blood in the human body cannot be underestimated, since it is responsible for the transfer of nutrients, microelements and gases necessary for the physiological course of cellular metabolic processes.

Main components

The structure of human blood contains two main components - plasma and several types of formed elements located in it.

As a result of centrifugation, you can see that this is a transparent liquid component of a yellowish color. Its volume reaches 52–60% of the total blood volume. The composition of plasma in the blood is 90% water, where proteins, inorganic salts, nutrients, hormones, vitamins, enzymes and gases are dissolved. And what does human blood consist of?

Blood cells are of the following types:

(red blood cells) - contained most among all cells, their importance is the transport of oxygen. The red color is due to the presence of hemoglobin in them.
(white blood cells) are part of the human immune system, protecting it from pathogenic factors.
(blood plates) – guarantee the physiological course of blood clotting.

Platelets are colorless plates without a nucleus. In fact, these are fragments of the cytoplasm of megakaryocytes (giant cells in the bone marrow), which are surrounded by a cell membrane. The shape of platelets is varied - oval, in the form of a sphere or rods. The function of platelets is to ensure blood clotting, that is, to protect the body from.

Blood is a rapidly regenerating tissue. The renewal of blood cells takes place in the hematopoietic organs, the main of which is located in the pelvic and long tubular bones of the bone marrow.

What tasks does blood perform?
There are six functions of blood in the human body:

Nutritional - blood delivers nutrients from the digestive organs to all cells of the body.

Excretory – the blood picks up and carries away decay and oxidation products from cells and tissues to the excretory organs.

Respiratory – transport of oxygen and carbon dioxide.

Protective – neutralization of pathogenic organisms and toxic products.

Regulatory – due to the transfer of hormones that regulate metabolic processes and the functioning of internal organs.

Maintaining homeostasis (constancy of the internal environment of the body) - temperature, environmental reaction, salt composition, etc.

The importance of blood in the body is enormous. The constancy of its composition and characteristics ensures the normal course of life processes. By changing its indicators, it is possible to identify the development of the pathological process in the early stages. We hope you learned what blood is, what it consists of and how it functions in the human body.

Blood and lymph are usually called the internal environment of the body, since they surround all cells and tissues, ensuring their vital activity. In relation to its origin, blood, like other body fluids, can be considered as sea water that surrounded the simplest organisms, closed inward and subsequently underwent certain changes and complications.

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

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

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

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

Basic physiological functions of blood.

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

1.Transport functions . These functions consist of the transfer of substances necessary for life (gases, nutrients, metabolites, hormones, enzymes, etc.) The transported substances can remain unchanged in the blood, or enter into certain, mostly unstable, compounds with proteins, hemoglobin, other components and transported in this state. Transport includes such functions as:

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

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

V) excretory (excretory ), which consists in the transfer of unnecessary metabolic products (metabolites), as well as excess salts, acid radicals and water to the places where they are excreted from the body;

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

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

A) phagocytic - blood leukocytes are able to devour (phagocytose) foreign cells and foreign bodies that enter the body;

b) immune - blood is the place where various kinds of antibodies are located, formed by lymphocytes in response to the entry of microorganisms, viruses, toxins and providing acquired and innate immunity.

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

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

A) pH maintenance ;

b) maintaining osmotic pressure;

V) temperature maintenance internal environment.

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

The amount of blood in the body. Circulating blood volume (CBV).

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

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

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

1.Blood plasma composition.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Physicochemical properties of blood

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

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

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

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

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

The functional system for maintaining blood pH (BPB) includes a number of anatomically heterogeneous organs, which together make it possible to achieve a very important beneficial result for the body - ensuring the constancy of the pH of blood and tissues. The appearance of acidic metabolites or alkaline substances in the blood is immediately neutralized by appropriate buffer systems, and at the same time, from specific chemoreceptors embedded both in the walls of blood vessels and in tissues, the central nervous system receives signals about the occurrence of a shift in blood reactions (if one has actually occurred). In the intermediate and medulla oblongata of the brain there are centers that regulate the constancy of the blood reaction. From there, commands are transmitted via afferent nerves and humoral channels to executive organs that can correct the disturbance of homeostasis. These organs include all excretory organs (kidneys, skin, lungs), which remove from the body both the acidic products themselves and the products of their reactions with buffer systems. In addition, the gastrointestinal tract organs take part in the activity of the FSrN, which can be both a place for the release of acidic products and a place from which the substances necessary to neutralize them are absorbed. Finally, the executive organs of the FSrN include the liver, where detoxification of potentially harmful products, both acidic and alkaline, occurs. It should be noted that in addition to these internal organs, there is also an external link in the FSrN - a behavioral one, when a person purposefully searches in the external environment for substances that he lacks to maintain homeostasis (“I want something sour!”). The diagram of this FS is shown in the diagram.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Introduction to the topic

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

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

Compound

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

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

Blood plasma, the composition and functions of which we are considering, is the necessary medium in which formed elements exist. Plasma consists of three main proteins - globulins, albumins and fibrinogen. It is interesting that it even contains gases in small quantities.

Red blood cells

The composition of blood and blood functions cannot be considered without a detailed study of erythrocytes - red cells. Under a microscope, they were found to resemble concave discs. They have no nuclei. The cytoplasm contains the hemoglobin protein, which is important for human health. If there is not enough of it, the person becomes anemic. Since hemoglobin is a complex substance, it consists of the heme pigment and globin protein. An important structural element is iron.

Red blood cells perform the most important function - they transport oxygen and carbon dioxide through the vessels. They are the ones who nourish the body, help it live and develop, because without air a person dies in a few minutes, and the brain, if red blood cells are not working enough, can experience oxygen starvation. Although red cells themselves do not have a nucleus, they still develop from nucleated cells. The latter mature in the red bone marrow. As red cells mature, they lose their nucleus and become formed elements. Interestingly, the life cycle of red blood cells is about 130 days. After this, they are destroyed in the spleen or liver. Bile pigment is formed from hemoglobin protein.

Platelets

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

Leukocytes

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

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

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

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

Properties of blood

Blood has certain properties. There are three most important ones:

Colloidal, which directly depend on the amount of protein in the plasma. It is known that protein molecules can hold water, therefore, thanks to this property, the liquid composition of the blood is stable.
Suspension: also related to the presence of protein and the ratio of albumin and globulin.
Electrolyte: affect osmotic pressure. Depends on the ratio of anions and cations.

Functions

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

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

The last function has several subfunctions that are worth considering separately.

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

The nutritional subfunction means the delivery of nutrients to tissues.

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

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

The composition of blood and the functions of blood cells determine a person’s health and well-being. A deficiency or excess of certain substances can lead to minor ailments such as dizziness or serious illnesses. Blood performs its functions clearly, the main thing is that the products of transportation are beneficial to the body.

Blood groups

We discussed the composition, properties and functions of blood in detail above. Now it’s worth talking about blood groups. Belonging to one group or another is determined by a set of specific antigenic properties of red blood cells. Each person has a certain blood type, which does not change throughout life and is congenital. The most important grouping is the division into four groups according to the “AB0” system and into two groups according to the Rh factor.

In the modern world, blood transfusions are very often required, which we will talk about below. So, for this process to be successful, the blood of the donor and recipient must match. However, compatibility does not solve everything; there are interesting exceptions. People with blood type I can be universal donors for people with any blood group. Those with blood group IV are universal recipients.

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

Blood transfusion

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

The approximate composition of blood and the functions of blood elements were known in ancient times. At that time, doctors also practiced transfusions, which often saved the patient’s life, but the mortality rate from this method of treatment was incredibly high due to the fact that the concept of blood group compatibility did not yet exist. However, death could not only occur as a result of this. Sometimes death occurred due to the fact that donor cells stuck together and formed lumps that clogged blood vessels and disrupted blood circulation. This effect of transfusion is called agglutination.

Blood diseases

The composition of blood and its main functions affect overall well-being and health. If there are any violations, various diseases may arise. Hematology deals with the study of the clinical picture of diseases, their diagnosis, treatment, pathogenesis, prognosis and prevention. However, blood diseases can also be malignant. They are studied by oncohematology.

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

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

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

Animal blood

The composition of blood and blood function in animals has its own differences. In invertebrate animals, the share of blood in the total body weight is approximately 20-30%. It is interesting that in vertebrates the same figure reaches only 2-8%. In the world of animals, blood is more diverse than in humans. We should also talk about the composition of the blood. The functions of blood are similar, but the composition can be completely different. There is iron-containing blood that flows in the veins of vertebrates. It is red in color, similar to human blood. Iron-containing blood based on hemerythrin is characteristic of worms. Spiders and various cephalopods are naturally endowed with blood based on hemocyanin, that is, their blood contains copper, not iron.

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

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

Definition of the blood system

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

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

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

Composition and amount of blood in the body

Blood is a liquid connective tissue that consists of a liquid part - and cells suspended in it - : (red blood cells), (white blood cells), (blood platelets). In an adult, formed elements of blood make up about 40-48%, and plasma - 52-60%. This ratio is called the hematocrit number (from the Greek. haima- blood, kritos- index). The composition of blood is shown in Fig. 1.

Rice. 1. Blood composition

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

Physicochemical properties of blood and plasma

How much blood is there in the human body?

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

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

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

Blood plasma: composition and properties

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

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

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

Concentration of hydrogen ions and regulation of blood pH

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

Thus, at a pH of 6.95, loss of consciousness occurs, and if these changes are not eliminated as soon as possible, then death is inevitable. If the pH becomes equal to 7.7, then severe convulsions (tetany) occur, which can also lead to death.

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

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

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

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

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

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

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

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

Blood is a liquid type of connective tissue that is in constant movement. Thanks to this, many of its functions are ensured - nutritional, protective, regulatory, humoral and others. Normally, formed elements of blood make up about 45%, the rest is plasma. In the article we will look at what particles vital connective tissue includes, as well as their main functions.

Blood functions

Blood cells are very important for the normal functioning of the entire body. Violation of this composition leads to the development of various diseases.

Blood functions:

humoral – transport of substances for regulation;
respiratory - responsible for the transfer of oxygen to the lungs and other organs, the removal of carbon dioxide;
excretory – ensures the elimination of harmful metabolic products;
thermoregulatory – transfer and redistribution of heat in the body;
protective – helps neutralize pathogenic microorganisms, participates in immune reactions;
homeostatic – maintaining all metabolic processes at a normal level;
nutritious - the transfer of nutrients from organs where they are synthesized to other tissues.

All these functions are provided thanks to leukocytes, erythrocytes, platelets and some other elements.

Red blood cells, or erythrocytes, are transport cells with a biconvex disc shape. Such a cell consists of hemoglobin and some other substances, due to which the blood flow ensures the transfer of oxygen to all tissues. Red blood cells take oxygen from the lungs, then carry it to the organs, returning from there with carbon dioxide.

The formation of red blood cells takes place in the red bone marrow of the long bones of the arms and legs (in childhood) and in the bones of the skull, spine and ribs (in adults). The total lifespan of one cell is about 90–120 days, after which the bodies succumb to hemolysis, which takes place in the tissues of the spleen and liver, and are excreted from the body.

Under the influence of various diseases, the formation of red blood cells is disrupted and their shape is distorted. This causes a decrease in the performance of their functions.

Red blood cells are the main transporter of oxygen in the body

Important! The study of the quantity and quality of red blood cells plays an important diagnostic role.

Leukocytes are white blood cells that perform a protective function. There are several types of these cells, differing in purpose, structure, origin and some other characteristics.

Leukocytes are produced in the red bone marrow and lymph nodes. Their role in the body is protection against viruses, bacteria, fungi and other pathogenic microorganisms.

Neutrophils

Neutrophils are one of the groups of blood cells. These cells are the most numerous type. They make up up to 96% of all leukocytes.

When a source of infection enters the body, these bodies quickly move to the location of the foreign microorganism. Due to rapid reproduction, these cells quickly neutralize viruses, bacteria and fungi, as a result of which they die. This phenomenon in medicine is called phagocytosis.

Eosinophils

The concentration of eosinophils in the blood is lower, but they perform an equally important protective function. After foreign cells enter the body, eosinophils quickly move to eliminate them to the affected area. They easily penetrate the tissues of blood vessels and absorb uninvited guests.

Another important function is the binding and absorption of certain allergy mediators, including histamine. That is, eosinophils perform an antiallergic role. In addition, they effectively fight helminths and helminthic infestations.

Monocytes

Functions of monocytes:

neutralization of microbial infections;
restoration of damaged tissues;
protection against tumor formation;
phagocytosis of affected and dead tissues;
toxic effect on helminthic infestations that have entered the body.

Monocytes are important blood cells that perform a protective function

Monocytes are responsible for the synthesis of interferon protein. It is interferon that blocks the spread of viruses and helps destroy the shell of pathogenic microorganisms.

Important! The life cycle of monocytes is short and lasts three days. After this, the cells penetrate into the tissue, where they turn into tissue macrophages.

Basophils

Like other blood cells, basophils are produced in the tissues of the red bone marrow. After synthesis, they enter the human bloodstream, where they remain for about 120 minutes, after which they are transferred to cellular tissues, where they perform their main functions, and remain for 8 to 12 days.

The main role of these cells is to promptly identify and neutralize allergens, stop their spread throughout the body, and call other granulocytes to the site of the spread of foreign bodies.

In addition to participating in allergic reactions, basophils are responsible for blood flow in thin capillaries. The role of cells in protecting the body from viruses and bacteria, as well as in the formation of immunity, is very small, despite the fact that their main function is phagocytosis. This type of leukocyte takes an active part in the process of blood clotting, increases vascular permeability, and actively participates in the contraction of certain muscles.

Lymphocytes are the most important cells of the immune system, performing a number of complex tasks. These include:

production of antibodies, destruction of pathogenic microflora;
the ability to distinguish between “own” and “foreign” cells in the body;
elimination of mutating cells;
ensuring sensitization of the body.

Immune cells are divided into T lymphocytes, B lymphocytes and NK lymphocytes. Each group performs its own function.

T lymphocytes

Based on the level of these bodies in the blood, one or another immune disorder can be determined. An increase in their number indicates increased activity of natural defenses, which indicates immunoproliferative disorders. A low level indicates immune dysfunction. During laboratory testing, the number of T-lymphocytes and other formed elements is taken into account, thanks to which it is possible to establish a diagnosis.

B lymphocytes

Cells of this species have a specific function. Their activation occurs only under conditions when certain types of pathogens penetrate the body. These could be strains of a virus, a particular type of bacterial infection, proteins or other chemicals. If the pathogen is of a different nature, B lymphocytes do not have any effect on it. That is, the main function of these bodies is the synthesis of antibodies and the implementation of humoral defense of the body.

Lymphocytes are the main immune defenders

NK lymphocytes

This type of antibody can react to any pathogenic microorganisms against which T lymphocytes are powerless. Due to this, NK lymphocytes are called natural killer cells. It is these bodies that effectively fight cancer cells. Today, active research is underway on this blood element in the field of cancer treatment.

Platelets

Platelets are small but very important blood cells, without which stopping bleeding and healing wounds would be impossible. These bodies are synthesized by splitting off small particles of cytoplasm from large structural formations - megakaryocytes located in the red bone marrow.

Platelets take an active part in the process of blood clotting, due to which wounds and abrasions tend to heal. Without this, any damage to the skin or internal organs would be fatal to humans.

When a vessel is damaged, platelets quickly stick together, forming blood clots that prevent further bleeding.

Important! In addition to wound healing, platelets help nourish vascular walls, take an active part in regeneration, and synthesize substances that catalyze the division and growth of skin cells during wound healing.

The norm of formed elements in the blood

To perform all the necessary functions of blood, the amount of all formed elements in it must meet certain standards. Depending on age, these indicators change. In the table you can find data on which numbers are considered normal.

Any deviations from the norm serve as a reason for further examination of the patient. To exclude false indicators, it is important for a person to follow all recommendations for donating blood for laboratory testing. The test should be taken in the morning on an empty stomach. In the evening before visiting the hospital, it is important to avoid spicy, smoked, salty foods and alcoholic beverages. Blood sampling is carried out exclusively in a laboratory using sterile instruments.

Regular testing and timely detection of certain disorders will help to diagnose various pathologies in a timely manner, carry out treatment, and maintain health for many years.