Blood, its composition and functions. Blood, its composition, properties and functions, the concept of the internal environment of the body

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 consider which particles include vital connective tissue, 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 everything 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 formed 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 it 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 penetrate tissue easily blood vessels, 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 immune system, performing a series 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 can determine certain immune disorders. An increase in their number indicates increased activity natural protection, 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 the virus, one type or another 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, main function these bodies - 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 ones. 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 which 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 drinks. Blood sampling is carried out exclusively in a laboratory using sterile instruments.

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

(blood platelets). In an adult, formed elements of blood make up about 40-48%, and plasma - 52-60%.

Blood is a liquid tissue. It has a red color, which is given to it by erythrocytes (red blood cells). The implementation of the main functions of the blood is ensured by maintaining an optimal plasma volume, a certain level of blood cellular elements (Fig. 1) and various plasma components.

Plasma devoid of fibrinogen is called serum.

Rice. 1. Formed elements of blood: a - cattle; b - chicken; 1 - red blood cells; 2, b — eosinophilic granulocytes; 3,8,11 - lymphocytes: medium, small, large; 4 - blood platelets; 5.9 - neutrophil granulocytes: segmented (mature), band (young); 7 - basophilic granulocyte; 10 - monocyte; 12 - erythrocyte nucleus; 13 - non-granular leukocytes; 14 - granular leukocytes

All blood cells- , and - are formed in the red bone marrow. Despite the fact that all blood cells are descendants of a single hematopoietic cell - fibroblasts, they perform various specific functions, at the same time, the common origin endowed them with general properties. Thus, all blood cells, regardless of their specificity, participate in the transport of various substances and perform protective and regulatory functions.

Rice. 2. Blood composition

Red blood cells in men are 4.0-5.0x 10 12 /l, in women 3.9-4.7x 10 12 /l; leukocytes 4.0-9.0x 10 9 /l; platelets 180-320x 10 9 /l.

Red blood cells

Erythrocytes, or red blood cells, were first discovered by Malpighi in the blood of a frog (1661), and Leeuwenhoek (1673) showed that they were also present in the blood of humans and mammals.

- nuclear-free red blood cells biconcave disc-shaped. Thanks to this shape and elasticity of the cytoskeleton, red blood cells can transport a large number of different substances and penetrate through narrow capillaries.

The red blood cell consists of stroma and a semipermeable membrane.

Basic integral part red blood cells (up to 95% of the mass) is hemoglobin, which gives the blood its red color and consists of globin protein and iron-containing heme. The main function of hemoglobin and red blood cells is the transport of oxygen (0 2) and carbon dioxide (CO 2).

There are about 25 trillion red blood cells in human blood. If you put all the red blood cells next to each other, you will get a chain about 200 thousand km long, which can encircle the globe along the equator 5 times. If you put all the red blood cells of one person on top of each other, you will get a “column” more than 60 km high.

Erythrocytes have the shape of a biconcave disk; when viewed in a cross section, they resemble dumbbells. This shape not only increases the surface of the cell, but also promotes faster and more uniform diffusion of gases across the cell membrane. If they had the shape of a ball, then the distance from the center of the cell to the surface would increase 3 times, and the total area of ​​erythrocytes would be 20% less. Red blood cells are highly elastic. They easily pass through capillaries that have half the diameter of the cell itself. The total surface of all red blood cells reaches 3000 m2, which is 1500 times greater than the surface of the human body. Such ratios of surface and volume contribute to the optimal performance of the main function of red blood cells - the transfer of oxygen from the lungs to the cells of the body.

Unlike other representatives of the chordate type, mammalian erythrocytes are anucleate cells. The loss of the nucleus led to an increase in the amount of the respiratory enzyme - hemoglobin. An aqueous red blood cell contains about 400 million hemoglobin molecules. Deprivation of the nucleus has led to the fact that the erythrocyte itself consumes 200 times less oxygen than its nuclear representatives (erythroblasts and normoblasts).

Men's blood contains an average of 5. 10 12 / l of red blood cells (5,000,000 in 1 μl), in women - about 4.5. 10 12 /l erythrocytes (4,500,000 in 1 μl).

Normally, the number of red blood cells is subject to slight fluctuations. With various diseases, the number of red blood cells may decrease. This condition is called erythropenia and is often accompanied by anemia or anemia. An increase in the number of red blood cells is called erythrocytosis.

Hemolysis and its causes

Hemolysis is the rupture of the red blood cell membrane and release into the plasma, due to which the blood acquires a lacquered tint. Under artificial conditions, hemolysis of red blood cells can be caused by placing them in hypotonic solution -osmotic hemolysis. For healthy people, the minimum limit of osmotic resistance corresponds to a solution containing 0.42-0.48% NaCl, while complete hemolysis (maximum limit of resistance) occurs at a concentration of 0.30-0.34% NaCl.

Hemolysis can be caused by chemical agents (chloroform, ether, etc.) that destroy the erythrocyte membrane - chemical hemolysis. Hemolysis often occurs in acetic acid poisoning. The venoms of some snakes have hemolyzing properties - biological hemolysis.

When the ampoule with blood is strongly shaken, destruction of the red blood cell membrane is also observed -mechanical hemolysis. It can occur in patients with prosthetic valves of the heart and blood vessels, and sometimes occurs when walking (marching hemoglobinuria) due to injury to red blood cells in the capillaries of the feet.

If red blood cells are frozen and then warmed up, hemolysis occurs, which is called thermal. Finally, when transfusing incompatible blood and the presence of autoantibodies to red blood cells develops immune hemolysis. The latter is the cause of anemia and is often accompanied by the release of hemoglobin and its derivatives in the urine (hemoglobinuria).

Erythrocyte sedimentation rate (ESR)

If blood is placed in a test tube, after adding substances that prevent clotting, then after some time the blood will separate into two layers: the upper one consists of plasma, and the lower one consists of formed elements, mainly red blood cells. Based on these properties.

Farreus proposed studying the suspension stability of erythrocytes by determining the rate of their sedimentation in the blood, the coagulability of which was eliminated by the preliminary addition of sodium citrate. This indicator is called “erythrocyte sedimentation rate (ESR)” or “erythrocyte sedimentation reaction (ESR)”.

The ESR value depends on age and gender. Normally, in men this figure is 6-12 mm per hour, in women - 8-15 mm per hour, in older people of both sexes - 15-20 mm per hour.

The greatest influence on the ESR value is exerted by the content of fibrinogen and globulin proteins: with an increase in their concentration, the ESR increases, since the electrical charge of the cell membrane decreases and they more easily “stick together” like coin columns. ESR increases sharply during pregnancy, when the fibrinogen content in plasma increases. This is a physiological increase; it is assumed that it provides a protective function of the body during gestation. An increase in ESR is observed during inflammatory, infectious and oncological diseases, as well as with a significant decrease in the number of red blood cells (anemia). A decrease in ESR in adults and children over 1 year of age is an unfavorable sign.

Leukocytes

- white blood cells. They contain a nucleus, do not have a permanent shape, have amoeboid mobility and secretory activity.

In animals, the content of leukocytes in the blood is approximately 1000 times less than erythrocytes. 1 liter of cattle blood contains approximately (6-10). 10 9 leukocytes, horses - (7-12)-10 9, pigs - (8-16)-10 9 leukocytes. The number of leukocytes in natural conditions fluctuates within wide limits and can increase after eating food, heavy muscular work, with severe irritation, pain, etc. An increase in the number of leukocytes in the blood is called leukocytosis, and a decrease is called leukopenia.

There are several types of leukocytes depending on their size, the presence or absence of granularity in the protoplasm, the shape of the nucleus, etc. Based on the presence of granularity in the cytoplasm, leukocytes are divided into granulocytes (granular) and agranulocytes (non-granular).

Granulocytes make up the majority of white blood cells and include neutrophils (stained with acidic and basic dyes), eosinophils (stained with acidic dyes) and basophils (stained with basic dyes).

Neutrophils capable of amoeboid movement, pass through the endothelium of capillaries, and actively move to the site of damage or inflammation. They phagocytose living and dead microorganisms and then digest them using enzymes. Neutrophils secrete lysosomal proteins and produce interferon.

Eosinophils neutralize and destroy toxins of protein origin, foreign proteins, antigen-antibody complexes. They produce the enzyme histaminase, absorb and destroy histamine. Their number increases when various toxins enter the body.

Basophils take part in allergic reactions, releasing heparin and histamine after encountering an allergen, which prevent blood clotting, dilate capillaries and promote resorption during inflammation. Their number increases with injuries and inflammatory processes.

Agranulocytes are divided into monocytes and lymphocytes.

Monocytes have pronounced phagocytic and bactericidal activity in acidic environment. Participate in the formation of the immune response. Their number increases during inflammatory processes.

Carry out reactions of cellular and humoral immunity. Capable of penetrating tissue and returning back to the blood, they live for several years. They are responsible for the formation of specific immunity and carry out immune surveillance in the body, maintaining the genetic constancy of the internal environment. On plasma membrane Lymphocytes have specific areas called receptors, due to which they are activated upon contact with foreign microorganisms and proteins. They synthesize protective antibodies, lyse foreign cells, provide a transplant rejection reaction and the body's immune memory. Their number increases with the penetration of microorganisms into the body. Unlike other leukocytes, lymphocytes mature in the red bone marrow, but later they undergo differentiation in lymphoid organs and tissues. Some lymphocytes differentiate in the thymus ( thymus) and therefore they are called T lymphocytes.

T lymphocytes are formed in the bone marrow, enter and undergo differentiation in the thymus, and then settle in the lymph nodes, spleen and circulate in the blood. There are several forms of T-lymphocytes: T-helpers (helpers), which interact with B-lymphocytes, turning them into plasma cells that synthesize antibodies and gamma globulins; T-suppressors (depressors), inhibiting excessive reactions of B-lymphocytes and maintaining a certain ratio different forms lymphocytes, and T-killers (killers), which interact with foreign cells and destroy them, forming cellular immune reactions.

B lymphocytes are formed in the bone marrow, but in mammals they undergo differentiation in the lymphoid tissue of the intestine, palatine and pharyngeal tonsils. When they encounter an antigen, B lymphocytes are activated, migrate to the spleen, lymph nodes, where they multiply and transform into plasma cells that produce antibodies and gamma globulins.

Null lymphocytes do not undergo differentiation in the organs of the immune system, but, if necessary, are able to transform into B and T lymphocytes.

The number of lymphocytes increases when microorganisms penetrate the body.

The percentage of individual forms of blood leukocytes is called leukocyte formula, or leicogrammoi.

Maintaining Consistency leukocyte formula peripheral blood is carried out due to the interaction of continuously occurring processes of maturation and destruction of leukocytes.

Lifespan of leukocytes different types lasts from several hours to several days, with the exception of lymphocytes, some of which live for several years.

Platelets

- small blood platelets. After formation in the red bone marrow, they enter the bloodstream. Platelets have mobility, phagocytic activity, and are involved in immune reactions. When destroyed, platelets release components of the blood coagulation system, participate in blood clotting, clot retraction and lysis of the resulting fibrin. They also regulate angiotrophic function thanks to the growth factor they contain. Under the influence of this factor, the proliferation of endothelial and smooth muscle cells of blood vessels increases. Platelets have the ability to adhesion (sticking) and aggregation (the ability to stick together).

Platelets are formed and develop in the red bone marrow. Their lifespan is on average 8 days, and then they are destroyed in the spleen. The number of these cells increases with trauma and vascular damage.

1 liter of blood in a horse contains up to 500. 10 9 platelets, in cattle - 600. 10 9, in pigs - 300. 10 9 platelets.

Blood constants

Basic blood constants

Blood, as a liquid tissue of the body, is characterized by many constants, which can be divided into soft and hard.

Soft (plastic) constants can change their value from the constant level over a wide range without significant changes in the vital activity of cells and body functions. Soft blood constants include: the amount of circulating blood, the ratio of plasma volumes and formed elements, the number of formed elements, the amount of hemoglobin, erythrocyte sedimentation rate, blood viscosity, relative density of blood, etc.

The amount of blood circulating through the vessels

Total blood in the body makes up 6-8% of body weight (4-6 l), of which about half circulates at rest in the body, the other half - 45-50% is in the depot (in the liver - 20%, in the spleen - 16% , in skin vessels - 10%).

The ratio of the volumes of blood plasma and formed elements is determined by centrifuging the blood in a hematocrit analyzer. Under normal conditions, this ratio is 45% formed elements and 55% plasma. This value is healthy person can undergo significant and lasting changes only when adapting to high altitudes. The liquid part of the blood (plasma), devoid of fibrinogen, is called serum.

Erythrocyte sedimentation rate

For men -2-10 mm/h, for women - 2-15 mm/h. The erythrocyte sedimentation rate depends on many factors: the number of erythrocytes, their morphological characteristics, the amount of charge, the ability to agglomerate (aggregate), protein composition plasma. The erythrocyte sedimentation rate is influenced by the physiological state of the body. For example, during pregnancy, inflammatory processes, emotional stress and other conditions, the erythrocyte sedimentation rate increases.

Blood viscosity

Caused by the presence of proteins and red blood cells. The viscosity of whole blood is 5, if the viscosity of water is taken as 1, and plasma - 1.7-2.2.

Specific gravity (relative density) of blood

Depends on the content of formed elements, proteins and lipids. The specific gravity of whole blood is 1.050, plasma - 1.025-1.034.

Hard constants

Their fluctuation is permissible in very small ranges, since deviation by insignificant values ​​leads to disruption of the vital activity of cells or the functions of the entire organism. Hard constants include the constancy of the ionic composition of the blood, the amount of proteins in the plasma, the osmotic pressure of the blood, the amount of glucose in the blood, the amount of oxygen and carbon dioxide in the blood, and the acid-base balance.

Constancy of blood ion composition

The total quantity is not organic matter blood plasma is about 0.9%. These substances include: cations (sodium, potassium, calcium, magnesium) and anions (chlorine, HPO 4, HCO 3 -). The cation content is a more rigid value than the anion content.

The amount of proteins in plasma

Functions of proteins:

  • create oncotic pressure of the blood, on which the exchange of water between the blood and the intercellular fluid depends;
  • determine blood viscosity, which affects the hydrostatic pressure of the blood;
  • fibrinogen and globulins take part in the blood clotting process;
  • the ratio of albumin and globulin affects the ESR value;
  • are important components protective function of blood (gamma globulins);
  • take part in the transport of metabolic products, fats, hormones, vitamins, heavy metal salts;
  • are an indispensable reserve for the construction of tissue proteins;
  • participate in maintaining acid-base balance, performing buffer functions.

The total amount of proteins in plasma is 7-8%. Plasma proteins are distinguished by structure and functional properties. They are divided into three groups: albumins (4.5%), globulins (1.7-3.5%) and fibrinogen (0.2-0.4%).

Blood osmotic pressure

Understands the force with which a solute holds or attracts a solvent. This force causes the movement of solvent through a semipermeable membrane from a less concentrated solution to a more concentrated one.

The osmotic pressure of the blood is 7.6 atm. It depends on the content of salts and water in the blood plasma and ensures its maintenance at the physiologically necessary level of concentration of various substances dissolved in liquid media body. Osmotic pressure promotes the distribution of water between tissues, cells and blood.

Solutions whose osmotic pressure is equal to the osmotic pressure of the cells are called isotonic, and they do not cause a change in cell volume. Solutions with higher osmotic pressure osmotic pressure cells are called hypertonic. They cause cells to shrink as a result of the transfer of some water from the cells into the solution. Solutions with lower osmotic pressure are called hypotonic. They cause an increase in cell volume as a result of the passage of water from solution into the cell.

Minor changes in the salt composition of blood plasma can be detrimental to the cells of the body and, above all, the cells of the blood itself due to changes in osmotic pressure.

Part of the osmotic pressure created by plasma proteins is oncotic pressure, the value of which is 0.03-0.04 atm., or 25-30 mm Hg. Oncotic pressure is a factor that promotes the transfer of water from tissues into the bloodstream. When the oncotic pressure of the blood decreases, water leaks out of the vessels into the interstitial space and leads to tissue edema.

The normal amount of glucose in the blood is 3.3-5.5 mmol/l.

Content of oxygen and carbon dioxide in the blood

Arterial blood contains 18-20 volume percent oxygen and 50-52 volume percent carbon dioxide, venous blood contains 12 volume percent oxygen and 55-58 volume percent carbon dioxide.

blood pH

Active regulation of blood is determined by the ratio of hydrogen and hydroxyl ions and is a rigid constant. To assess the active blood reaction, use pH value, equal to 7.36 (in arterial blood 7.4, in the venous - 7.35). An increase in the concentration of hydrogen ions leads to a shift in the blood reaction to the acidic side, and is called acidosis. An increase in the concentration of hydrogen ions and an increase in the concentration of hydroxyl ions (OH) leads to a shift in the reaction to the alkaline side, and is called alkalosis.

Maintaining blood constants at a certain level is carried out according to the principle of self-regulation, which is achieved by the formation of appropriate functional systems.

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 unbreakable bond formed elements of blood with 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 following features: its constituent parts are formed outside of 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 various physiological conditions, so 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.). Transported substances can remain unchanged in the blood, or enter into one or another, for the most part, unstable, compounds with proteins, hemoglobin, and other components and are 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).

Currently available precise methods to determine 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 vascular wall in fabric (dyes, polyvinylpyrrolidone, iron dextran complex, etc.) 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).

The introduction of fluid into the blood increases by a short time its volume. 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, thanks to the complex activity of various physiological systems body, the composition of plasma normally does not undergo significant changes.

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. General content blood proteins are 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 participation in coagulation processes (this plasma factors blood clotting). 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 factional composition plasma proteins. 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 when 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 important role in maintaining acid-base balance and osmotic blood pressure.

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 normal calcium levels in the blood occurs with the participation of the hormone parathyroid glands, 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 have 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 normal course 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. Alkaline reserve of blood plasma in healthy body 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, to the number executive bodies FSrN also includes the liver, where detoxification of potentially harmful foods, both acidic and alkaline, occurs. It should be noted that in addition to these internal organs, the FSrN also has an external link - behavioral, when a person purposefully searches for external environment 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 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 not determined chemical nature substances, 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 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 passable for water and crystalloids, it is the oncotic pressure of proteins that is most effective factor that retains water in 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. Of the other executive bodies of the FSOD, it is necessary to name the bodies digestive tract, in which both the removal of excess salts and water and the absorption of products necessary to restore 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 salt, sea water) dehydration 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 body cells consume large-molecular nutrients, and allocate in return significantly larger number molecules of low molecular weight 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 has practical clinical significance, since ESR changes noticeably under certain conditions and diseases. Thus, ESR greatly accelerates in women during pregnancy, in patients with tuberculosis, inflammatory diseases. When blood stands, red blood cells stick together with each other (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. Aggregation of erythrocytes, reflecting the dynamics of the suspension properties of blood, is one of the oldest defense mechanisms. In invertebrates, erythrocyte aggregation plays a leading role in the processes of hemostasis; during an inflammatory reaction, this leads to the development of stasis (stopping blood flow in the border areas), 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 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. IN physiological conditions blood viscosity in vitro increases (up to 70%) after strenuous physical work and is a consequence of changes colloidal properties 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 value, then the heart would have to develop 30-40 times more power to push blood through the vascular system, since viscosity is involved in the formation of peripheral resistance.

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.

Composition and properties of blood.

Blood- the internal environment of the body, which ensures homeostasis, reacts most early and sensitively to tissue damage. Blood is a mirror of homeostasis and blood testing is mandatory for any patient; indicators of blood changes are the most informative and play a large role in the diagnosis and prognosis of the course of diseases.

Blood distribution:

50% in organs abdominal cavity and pelvis;

25% in organs chest cavity;

25% on the periphery.

2/3 in venous vessels, 1/3 in arterial vessels.

Functions blood

1. Transport – transfer of oxygen and nutrients to organs and tissues and metabolic products to the excretory organs.

2. Regulatory – ensuring humoral and hormonal regulation of the functions of various systems and tissues.

3. Homeostatic – maintaining body temperature, acid-base balance, water-salt metabolism, tissue homeostasis, tissue regeneration.

4. Secretory – formation of biologically active substances by blood cells.

5. Protective - ensuring immune reactions, blood and tissue barriers against infection.

Properties of blood.

1. Relative constancy of circulating blood volume.

The total amount of blood depends on body weight and in the body of an adult it is normally 6–8%, i.e. approximately 1/130 of body weight, which for a body weight of 60–70 kg is 5–6 l. In a newborn – 155% of the mass.

In diseases, blood volume may increase - hypervolemia or decrease - hypovolemia. In this case, the ratio of formed elements and plasma can be maintained or changed.

Losing 25–30% of blood is life-threatening. Lethal - 50%.

2. Blood viscosity.

The viscosity of blood is due to the presence of proteins and formed elements, especially red blood cells, which, when moving, overcome the forces of external and internal friction. This indicator increases with blood thickening, i.e. loss of water and increase in the number of red blood cells. Viscosity blood plasma is 1.7–2.2, and whole blood – about 5 conventional units in relation to water. Relative density(specific gravity) of whole blood ranges from 1.050-1.060.

3. Suspension property.

Blood is a suspension in which the formed elements are suspended.

Factors providing this property:

The number of formed elements, the more there are, the more pronounced the suspension properties of blood;

Blood viscosity - the higher the viscosity, the greater the suspension properties.

An indicator of suspension properties is the erythrocyte sedimentation rate (ESR). Average erythrocyte sedimentation rate (ESR)) in men 4–9 mm/hour, in women – 8–10 mm/hour.

4. Electrolyte properties.

This property provides a certain amount of osmotic pressure in the blood due to the content of ions. Osmotic pressure is a fairly constant indicator, despite its slight fluctuations due to the transition from plasma to tissues of large molecular substances (amino acids, fats, carbohydrates) and the entry of low molecular weight products of cellular metabolism from tissues into the blood.

5. Relative constancy of the acid-base composition of the blood (pH) (acid-base balance).

The constancy of the blood reaction is determined by the concentration of hydrogen ions. The constancy of the pH of the internal environment of the body is due to the combined action of buffer systems and a number of physiological mechanisms. The latter include the respiratory activity of the lungs and the excretory function of the kidneys.

The most important blood buffer systems are bicarbonate, phosphate, protein and most powerful hemoglobin. The buffer system is a conjugate acid-base pair consisting of an acceptor and donor of hydrogen ions (protons).

Blood has a slightly alkaline reaction. It has been established that the normal state corresponds to a certain range of fluctuations in blood pH - from 7.37 to 7.44 with an average value of 7.40, arterial blood pH is 7.4; and venous, due to great content it contains carbon dioxide - 7.35.

Alkalosis- increase in blood pH (and other body tissues) due to the accumulation of alkaline substances.

Acidosis- decrease in blood pH as a result of insufficient excretion and oxidation of organic acids (their accumulation in the body).

6. Colloidal properties.

They lie in the ability of proteins to retain water in the vascular bed - hydrophilic finely dispersed proteins have this property.

Blood composition.

1. Plasma (liquid intercellular substance) 55-60%;

2. Formed elements (cells located in it) – 40-45%.

Blood plasma is the liquid remaining after the formed elements are removed from it.

Blood plasma contains 90–92% water and 8–10% dry matter. It contains different in their properties and functional significance protein substances: albumins (4.5%), globulins (2–3%) and fibrinogen (0.2–0.4%), as well as 0.9% salts, 0.1 % glucose. The total amount of proteins in human blood plasma is 7–8%. Blood plasma also contains enzymes, hormones, vitamins and other substances necessary for the body.

Figure - Blood cells:

1 - basophilic granulocyte; 2 - acidophilic granulocyte; 3 - segmented neutrophilic granulocyte; 4 - erythrocyte; 5 - monocyte; 6 - platelets; 7 - lymphocyte

A sharp decrease in the amount of glucose in the blood (up to 2.22 mmol/l) leads to increased excitability of brain cells and the appearance of seizures. A further decrease in blood glucose leads to impaired breathing, circulation, loss of consciousness and even death.

Blood plasma minerals are NaCl, KCI, CaCl NaHCO 2, NaH 2 PO 4 and other salts, as well as ions Na +, Ca 2+, K +, etc. The constancy of the ionic composition of the blood ensures the stability of osmotic pressure and the preservation of the volume of fluid in the blood and body cells. Bleeding and loss of salts are dangerous for the body and cells.

The formed elements (cells) of blood include: erythrocytes, leukocytes, platelets.

Hematocrit- part of the blood volume that accounts for the formed elements.

The message on the topic “Composition and functions of blood”, briefly outlined in this article, will tell you about the most important components of the type of connective tissue of the body.

Message: “Composition and functions of blood”

Blood is a connective tissue that consists of intercellular liquid substance, including plasma and suspended cells. Blood in the human body makes up 1/13 of body weight, which is about 4.5–5 liters. Blood plasma is a yellowish translucent liquid. It consists of water, minerals and organic substances: fats, proteins, glucose, vitamins, hormones, amino acids and metabolic products.

What is the blood composition?

In addition to plasma, blood contains the following formed cells:

  • Red blood cells

These are red anucleate blood cells in the form of biconcave discs. Their cytoplasm contains hemoglobin, which is responsible for the amount of iron in the body. The main function of these cells is to transport carbon dioxide and oxygen. They develop in the bone red marrow. The lifespan of red blood cells is from 120 to 130 days, after which they are destroyed in the spleen, and bile pigments are formed from hemoglobin.

  • Leukocytes

These are white blood cells without a permanent shape and with a nucleus. They develop in the spleen, red bone marrow and lymph nodes. They live for 2-4 days, after which they are destroyed in the spleen. The main function of these cells is protection against foreign proteins, bacteria and foreign bodies. White blood cells absorb harmful microorganisms and destroy them. This process is called phagocytosis.

  • Platelets

These are nuclear-free, colorless cells round shape. They play an important role in the blood clotting process. When blood vessels are damaged, platelets are destroyed. These cells develop in the red bone marrow.

Blood also performs the following functions:

  • Transport

It transports carbon dioxide, oxygen and nutrients to the organs after they are absorbed into the intestines. Thanks to this, metabolism is ensured, the supply of organs and the transfer of metabolic breakdown products from the body by the liver, kidneys and lungs. Blood also carries hormones.

  • Homeostasis

This connective tissue maintains the balance between cells, the circulatory system, and the extracellular environment. Its acid-base balance is regulated by the kidneys, liver and lungs. Blood also maintains body temperature. Thanks to it, blood clots dissolve in the body, and a physiological coagulation system exists.