What is blood. The composition of the blood and a brief description of the constituent elements. The structure of the blood system: types of hemoglobin

Blood is liquid connective tissue red color, which is constantly in motion and performs many complex and important functions for the body. It constantly circulates in the circulatory system and carries the necessary metabolic processes gases and substances dissolved in it.

Blood is made up of plasma and a suspension of special blood cells in it. Plasma is clear liquid yellowish color accounting for more than half of the total blood volume. It contains three main types shaped elements:

Erythrocytes - red cells that give the blood a red color due to the hemoglobin they contain;

Leukocytes - white cells;

Platelets are platelets.

Arterial blood, which comes from the lungs to the heart and then spreads to all organs, is enriched with oxygen and has a bright scarlet color. After the blood gives oxygen to the tissues, it returns through the veins to the heart. Deprived of oxygen, it becomes darker.

AT circulatory system an adult human circulates about 4 to 5 liters of blood. Approximately 55% of the volume is occupied by plasma, the rest is accounted for by formed elements, while most make up erythrocytes - more than 90%.

Blood is a viscous substance. Viscosity depends on the amount of proteins and red blood cells in it. This quality affects blood pressure and speed of movement. The density of blood and the nature of the movement of formed elements determine its fluidity. Blood cells move in different ways. They can move in groups or singly. RBCs can move either individually or in whole "stacks", like stacked coins, as a rule, create a flow in the center of the vessel. White cells move singly and usually stay near the walls.

Composition of the blood

Plasma is a liquid component of a light yellow color, which is due to a small amount of bile pigment and other colored particles. Approximately 90% it consists of water and approximately 10% of organic matter and minerals dissolved in it. Its composition is not constant and varies depending on food taken, the amount of water and salts. The composition of substances dissolved in plasma is as follows:

Organic - about 0.1% glucose, about 7% proteins and about 2% fats, amino acids, lactic and uric acid and others;

Minerals make up 1% (anions of chlorine, phosphorus, sulfur, iodine and cations of sodium, calcium, iron, magnesium, potassium.

Plasma proteins take part in the exchange of water, distribute it between the tissue fluid and blood, give blood viscosity. Some of the proteins are antibodies and neutralize foreign agents. An important role is given to the soluble protein fibrinogen. It takes part in the process of blood coagulation, turning under the influence of coagulation factors into insoluble fibrin.

In addition, there are hormones in plasma that are produced by glands. internal secretion, and other bioactive elements necessary for the functioning of body systems. Plasma devoid of fibrinogen is called blood serum.

Erythrocytes. The most numerous blood cells, making up about 44-48% of its volume. They have the form of discs, biconcave in the center, with a diameter of about 7.5 microns. Cell Shape Provides Efficiency physiological processes. Due to the concavity, the surface area of ​​the sides of the erythrocyte increases, which is important for gas exchange. Mature cells do not contain nuclei. The main function of red blood cells is the delivery of oxygen from the lungs to the tissues of the body.

Their name is translated from Greek as "red". Red blood cells owe their color to a very complex protein, hemoglobin, which is able to bind with oxygen. Hemoglobin consists of a protein part, which is called globin, and a non-protein part (heme), which contains iron. It is thanks to iron that hemoglobin can attach oxygen molecules.

Erythrocytes are produced in bone marrow. The term of their full maturation is approximately five days. The lifespan of red cells is about 120 days. RBC destruction occurs in the spleen and liver. Hemoglobin is broken down into globin and heme. Iron ions are released from the heme, return to the bone marrow and go to the production of new red blood cells. Heme without iron is converted into the bile pigment bilirubin, which enters the digestive tract with bile.

A decrease in the level of red blood cells in the blood leads to a condition such as anemia, or anemia.

Leukocytes are colorless peripheral blood cells that protect the body from external infections and pathologically altered own cells. White bodies are divided into granular (granulocytes) and non-granular (agranulocytes). The former include neutrophils, basophils, eosinophils, which are distinguished by their reaction to different dyes. To the second - monocytes and lymphocytes. Granular leukocytes have granules in the cytoplasm and a nucleus consisting of segments. Agranulocytes are devoid of granularity, their nucleus usually has a regular rounded shape.

Granulocytes are produced in the bone marrow. After maturation, when granularity and segmentation are formed, they enter the blood, where they move along the walls, making amoeboid movements. They protect the body mainly from bacteria, are able to leave the vessels and accumulate in the foci of infections.

Monocytes are large cells that form in the bone marrow, lymph nodes, and spleen. Their main function is phagocytosis. Lymphocytes are small cells that are divided into three types (B-, T, O-lymphocytes), each of which performs its own function. These cells produce antibodies, interferons, macrophage activating factors, and kill cancer cells.

Platelets are small, nuclear-free, colorless plates that are fragments of megakaryocyte cells found in the bone marrow. They can be oval, spherical, rod-shaped. Life expectancy is about ten days. The main function is participation in the process of blood coagulation. Platelets secrete substances that take part in a chain of reactions that are triggered by damage blood vessel. As a result, the fibrinogen protein turns into insoluble fibrin strands, in which blood elements become entangled and a blood clot forms.

Blood functions

It is unlikely that anyone doubts that blood is necessary for the body, but why it is needed, perhaps not everyone can answer. This liquid tissue performs several functions, including:

Protective. main role leukocytes, namely neutrophils and monocytes, play in protecting the body from infections and damage. They rush and accumulate at the site of damage. Their main purpose is phagocytosis, that is, the absorption of microorganisms. Neutrophils are microphages, and monocytes are macrophages. Other types of white blood cells - lymphocytes - produce antibodies against harmful agents. In addition, leukocytes are involved in the removal of damaged and dead tissues from the body.

Transport. Blood supply affects almost all processes occurring in the body, including the most important - respiration and digestion. With the help of blood, oxygen is transferred from the lungs to the tissues and carbon dioxide from the tissues to the lungs, organic substances from the intestines to the cells, end products, which are then excreted by the kidneys, transportation of hormones and other bioactive substances.

Temperature regulation. Man needs blood to maintain constant temperature body, the norm of which is in a very narrow range - about 37 ° C.

Blood (haema, sanguis) is a liquid tissue consisting of plasma and blood cells suspended in it. The blood is enclosed in a system of vessels and is in a state of continuous movement. Blood, lymph, interstitial fluid are the 3 internal media of the body, which wash all the cells, supplying them with the substances necessary for life, and carry away the end products of metabolism. The internal environment of the body is constant in its composition and physico-chemical properties. permanence internal environment organism is called homeostasis and is necessary condition life. Homeostasis is regulated by the nervous and endocrine systems. The cessation of blood flow during cardiac arrest leads the body to death.

Blood functions:

Transport (respiratory, nutritional, excretory)

Protective (immune, protection against blood loss)

Thermoregulating

Humoral regulation of functions in the body.

QUANTITY OF BLOOD, PHYSICO-CHEMICAL PROPERTIES OF BLOOD

Quantity

Blood makes up 6-8% of body weight. Newborns have up to 15%. On average, a person has 4.5 - 5 liters. Blood circulating in the vessels peripheral , part of the blood is contained in the depot (liver, spleen, skin) - deposited . The loss of 1/3 of the blood leads to the death of the organism.

Specific gravity(density) of blood - 1,050 - 1,060.

It depends on the amount of red blood cells, hemoglobin and proteins in the blood plasma. It increases with thickening of the blood (dehydration, exercise). A decrease in the specific gravity of blood is observed with the influx of fluid from the tissues after blood loss. In women, the specific gravity of the blood is slightly lower, because they have a lower number of red blood cells.

Blood viscosity 3- 5, exceeds the viscosity of water by 3 - 5 times (the viscosity of water at a temperature of + 20 ° C is taken as 1 conventional unit).

Plasma viscosity - 1.7-2.2.

Blood viscosity depends on the number of red blood cells and plasma proteins (mainly

fibrinogen) in the blood.

depends on the viscosity of the blood rheological properties blood - blood flow velocity and

peripheral blood resistance in the vessels.

Viscosity has a different value in different vessels (highest in venules and

veins, lower in arteries, lowest in capillaries and arterioles). If

viscosity would be the same in all vessels, then the heart would have to develop

30-40 times more power to push blood through the entire vascular

Viscosity increases with thickening of the blood, dehydration, after physical

loads, with erythremia, some poisonings, in venous blood, with the introduction

drugs - coagulants (drugs that enhance blood clotting).

Viscosity decreases with anemia, with the influx of fluid from tissues after blood loss, with hemophilia, with fever, in arterial blood, with the introduction heparin and other anticoagulants.

Environment reaction (pH) - fine 7,36 - 7,42. Life is possible if the pH is between 7 and 7.8.

The condition in which there is an accumulation of acid equivalents in the blood and tissues is called acidosis (acidification), At the same time, blood pH decreases (less than 7.36). acidosis may be :

gas - with the accumulation of CO 2 in the blood (CO 2 + H 2 O<->H 2 CO 3 - accumulation of acid equivalents);

metabolic (accumulation of acid metabolites, for example, in diabetic coma, the accumulation of acetoacetic and gamma-aminobutyric acids).

Acidosis leads to CNS inhibition, coma and death.

The accumulation of alkaline equivalents is called alkalosis (alkalinization)- an increase in pH greater than 7.42.

Alkalosis can also be gas , with hyperventilation of the lungs (if too much a large number of CO 2), metabolic - with the accumulation of alkaline equivalents and excessive excretion of acidic ones (uncontrollable vomiting, diarrhea, poisoning, etc.) Alkalosis leads to overexcitation of the central nervous system, muscle cramps and death.

Maintaining the pH is achieved through blood buffer systems that can bind hydroxyl (OH-) and hydrogen ions (H +) and thus keep the blood reaction constant. The ability of buffer systems to counteract the pH shift is explained by the fact that when they interact with H+ or OH-, compounds are formed that have a weakly pronounced acidic or basic character.

The main buffer systems of the body:

protein buffer system (acidic and alkaline proteins);

hemoglobin (hemoglobin, oxyhemoglobin);

bicarbonate (bicarbonates, carbonic acid);

phosphate (primary and secondary phosphates).

Osmotic blood pressure = 7.6-8.1 atm.

It is being created mostly sodium salts and etc. mineral salts dissolved in the blood.

Due to osmotic pressure, water is distributed evenly between cells and tissues.

Isotonic solutions are called solutions. osmotic pressure which is equal to the osmotic pressure of the blood. In isotonic solutions, erythrocytes do not change. Isotonic solutions are: saline 0.86% NaCl, Ringer's solution, Ringer-Locke's solution, etc.

in a hypotonic solution(the osmotic pressure of which is lower than in the blood), water from the solution goes into the red blood cells, while they swell and collapse - osmotic hemolysis. Solutions with higher osmotic pressure are called hypertensive, erythrocytes in them lose H 2 O and shrivel.

oncotic blood pressure due to plasma proteins (mainly albumin) Normally is 25-30 mmHg Art.(average 28) (0.03 - 0.04 atm.). Oncotic pressure is the osmotic pressure of blood plasma proteins. It is part of the osmotic pressure (is 0.05% of

osmotic). Thanks to him, water is retained in the blood vessels (vascular bed).

With a decrease in the amount of proteins in the blood plasma - hypoalbuminemia (in case of impaired liver function, hunger), oncotic pressure decreases, water leaves the blood through the wall of blood vessels in the tissue, and oncotic edema occurs ("hungry" edema).

ESR- sedimentation rate of erythrocytes, expressed in mm/h. At men ESR is normal - 0-10 mm/hour , among women - 2-15 mm/hour (in pregnant women up to 30-45 mm / hour).

ESR increases with inflammatory, purulent, infectious and malignant diseases, is normally increased in pregnant women.

BLOOD COMPOSITION

Formed elements of the blood - blood cells, make up 40 - 45% of the blood.

Blood plasma is a liquid intercellular substance of blood, it makes up 55-60% of blood.

The ratio of plasma and blood cells is called hematocritindex, because it is determined using hematocrit.

When blood stands in a test tube, the formed elements settle to the bottom, and the plasma remains on top.

FORMED BLOOD ELEMENTS

erythrocytes (red blood cells), leukocytes (white blood cells), platelets (red blood plates).

erythrocytes are red blood cells without a nucleus

the shape of a biconcave disc, 7-8 microns in size.

They are formed in the red bone marrow, live for 120 days, are destroyed in the spleen (“erythrocyte graveyard”), liver, and macrophages.

Functions:

1) respiratory - due to hemoglobin (transfer of O 2 and CO 2);

nutritional - can transport amino acids and other substances;

protective - able to bind toxins;

enzymatic - contain enzymes. Quantity erythrocytes are normal

in men in 1 ml - 4.1-4.9 million.

in women in 1 ml - 3.9 million.

in newborns in 1 ml - up to 6 million.

in the elderly in 1 ml - less than 4 million.

An increase in the number of red blood cells is called erythrocytosis.

Types of erythrocytosis:

1.Physiological(normal) - in newborns, residents of mountainous areas, after eating and exercise.

2. Pathological- in violation of hematopoiesis, erythremia (hemoblastosis - neoplastic diseases blood).

A decrease in the number of red blood cells in the blood is called erythropenia. It can be after blood loss, impaired formation of red blood cells

(iron deficiency, B!2 deficiency, folic acid deficiency anemia) and increased destruction of red blood cells (hemolysis).

HEMOGLOBIN (Hb) is a red respiratory pigment found in erythrocytes. Synthesized in the red bone marrow, destroyed in the spleen, liver, macrophages.

Hemoglobin consists of a protein - globin and 4 heme molecules. gem- non-protein part of Hb, contains iron, which combines with O 2 and CO 2. One hemoglobin molecule can attach 4 O 2 molecules.

The norm of the amount of Hb in the blood in men up to 132-164 g/l, in women 115-145 g/l. Hemoglobin decreases - with anemia (iron deficiency and hemolytic), after blood loss, increases - with blood clotting, B12 - folic deficiency anemia, etc.

Myoglobin is muscle hemoglobin. Plays an important role in the supply of O 2 to skeletal muscles.

Functions of hemoglobin: - respiratory - transport of oxygen and carbon dioxide;

enzymatic - contains enzymes;

buffer - is involved in maintaining the pH of the blood. Hemoglobin compounds:

1.physiological compounds of hemoglobin:

a) Oxyhemoglobin: Hb + O 2<->NIO 2

b) Carbohemoglobin: Hb + CO 2<->HCO 2 2. pathological hemoglobin compounds

a) Carboxyhemoglobin- connection with carbon monoxide, is formed during carbon monoxide poisoning (CO), irreversibly, while Hb is no longer able to carry O 2 and CO 2: Hb + CO -> HbO

b) Methemoglobin(Met Hb) - connection with nitrates, the connection is irreversible, formed during poisoning with nitrates.

HEMOLYSIS - this is the destruction of red blood cells with the release of hemoglobin to the outside. Types of hemolysis:

1. Mechanical hemolysis - can occur when shaking a test tube with blood.

2. Chemical hemolysis - with acids, alkalis, etc.

Z. Osmotic hemolysis - in a hypotonic solution, the osmotic pressure of which is lower than in the blood. In such solutions, water from the solution goes into the erythrocytes, while they swell and collapse.

4. Biological hemolysis - with a transfusion of an incompatible blood type, with snake bites (venom has a hemolytic effect).

Hemolyzed blood is called "lacquer", the color is bright red. hemoglobin enters the blood. Hemolyzed blood is unsuitable for analysis.

leukocytes- these are colorless (white) blood cells, containing a nucleus and protoplasm. They are formed in the red bone marrow, live 7-12 days, are destroyed in the spleen, liver, and macrophages.

Functions of leukocytes: immune defense, phagocytosis of foreign particles.

Properties of leukocytes:

Amoeba mobility.

Diapedesis - the ability to pass through the wall of blood vessels in the tissue.

Chemotaxis - movement in tissues to the focus of inflammation.

The ability to phagocytosis - the absorption of foreign particles.

In the blood of healthy people at rest white blood cell count ranges from 3.8-9.8 thousand in 1 ml.

An increase in the number of white blood cells in the blood is called leukocytosis.

Types of leukocytosis:

Physiological leukocytosis (normal) - after eating and exercise.

Pathological leukocytosis - occurs with infectious, inflammatory, purulent processes, leukemia.

Decrease in the number of leukocytes called in the blood leukopenia, can be with radiation sickness, exhaustion, aleukemic leukemia.

The percentage of types of leukocytes among themselves is called leukocyte count.

In order for the body to function optimally, all components and organs must be in a certain proportion. Blood is one of the types of tissues with a characteristic composition. Constantly moving, the blood performs a lot of the most important functions for the body, and also carries gases and elements through the circulatory system.

What components does it consist of?

Speaking briefly about the composition of blood, plasma and its constituent cells are the defining substances. Plasma is a clear liquid that makes up about 50% of the volume of blood. Plasma devoid of fibrinogen is called serum.

There are three types of formed elements in the blood:

• red blood cells- red cells. Red blood cells get their color from the hemoglobin they contain. The amount of hemoglobin in peripheral blood is approximately 130 - 160 g / l (male) and 120 - 140 g / l (female);
• - white cells
• - blood plates.

Arterial blood is characterized by a bright scarlet color. Penetrating from the lungs to the heart, arterial blood It spreads through the organs, enriching them with oxygen, and then returns to the heart through the veins. With a lack of oxygen, the blood darkens.

The circulatory system of an adult contains 4-5 liters of blood, 55% of which is plasma, and 45% is formed elements, with erythrocytes representing the majority (about 90%).

The viscosity of blood is proportional to the proteins and red blood cells it contains, and their quality affects blood pressure. Blood cells move either in groups or singly. Erythrocytes have the ability to move singly or "flocks", forming a stream in the central part of the vessel. Leukocytes usually move singly, adhering to the walls.

Blood functions

This liquid connective tissue, consisting of different elements, carries out the most important missions:

1. protective function. Leukocytes occupy the palm, protecting the human body from infection, concentrating in the damaged part of the body. Their purpose is fusion with microorganisms (phagocytosis). Leukocytes also contribute to the removal of altered and dead tissues from the body. Lymphocytes produce antibodies against dangerous agents.
2. transport function. The supply of blood affects virtually all processes of the functioning of the body.

Blood facilitates movement:

• Oxygen from lungs to tissues;
• Carbon dioxide from tissues to lungs;
• Organic matter from the intestines to the cells;
• End products excreted by the kidneys;
• Hormones;
• other active substances.

1. Temperature balance regulation. People need blood to maintain their body temperature within 36.4° - 37°C.

What is blood made of?

Plasma

The blood contains light yellow plasma. Its color can be explained low content bile pigment and other particles.

What is the composition of plasma? About 90% of plasma consists of water, and the remaining 10% belongs to dissolved organic elements and minerals.

Plasma contains the following solutes:

• Organic - consist of glucose (0.1%) and proteins (approximately 7%);
• Fats, amino acids, lactic and uric acids, etc. make up approximately 2% of plasma;
• Minerals - up to 1%.

It should be remembered: the composition of the blood varies depending on the products consumed and therefore is a variable value.

The volume of blood is:

If a person is in calm state, then the blood flow becomes much lower, since the blood partially remains in the venules and veins of the liver, spleen, and lungs.

The volume of blood remains relatively stable in the body. The rapid loss of 25 - 50% of the blood can provoke the death of the body - that's why in such cases, doctors resort to emergency transfusion.

Plasma proteins are actively involved in water exchange. Antibodies form a certain percentage of proteins that neutralize foreign elements.

Fibrinogen (soluble protein) affects blood clotting and is transformed into fibrin, unable to dissolve. Plasma contains hormones that produce endocrine glands and other bioactive elements that are very necessary for the body.

red blood cells

The most numerous cells, constituting 44% - 48% of the blood volume. Red blood cells get their name from the Greek word for red.

This color was provided to them by the most complex structure of hemoglobin, which has the ability to interact with oxygen. Hemoglobin has protein and non-protein parts.

The protein part contains iron, due to which hemoglobin attaches molecular oxygen.

By structure, erythrocytes resemble discs twice concave in the middle with a diameter of 7.5 microns. Due to such a structure, efficient processes, and due to concavity, the plane of the erythrocyte increases - all this is necessary for gas exchange. There are no nuclei in mature erythrocyte cells. The transport of oxygen from the lungs to tissues is the main mission of red blood cells.

Red blood cells are produced by the bone marrow.

Fully maturing in 5 days, the erythrocyte functions fruitfully for about 4 months. RBCs are broken down in the spleen and liver, and hemoglobin is broken down into globin and heme.

So far, science is not able to accurately answer the question: what transformations does globin then undergo, but iron ions released from heme again produce erythrocytes. Transforming into bilirubin (bile pigment), heme enters the gastrointestinal tract with bile. An insufficient number of red blood cells provokes anemia.

Colorless cells that protect the body from infection and painful cell degeneration. White bodies are granular (granulocytes) and non-granular (agranulocytes).

The granulocytes are:

• Neutrophils;
• Basophils;
• Eosinophils.

Differing in response to various dyes.

For agranulocytes:

• Monocytes;

Granular leukocytes have a granule in the cytoplasm and a nucleus with several sections. Agranulocytes are non-granular, include a rounded nucleus.

Granulocytes are produced by the bone marrow. The maturation of granulocytes is evidenced by their granular structure and the presence of segments.

Granulocytes penetrate the blood, moving along the walls with amoeboid movements. They can leave vessels and concentrate in the foci of infection.

Monocytes

Act as phagocytosis. These are larger cells that form in the bone marrow, lymph nodes, and spleen.

Smaller cells, subdivided into 3 types (B-, 0- and T). Each type of cell performs a specific function:

• Antibodies are produced;
• Interferons;
• Macrophages are activated;
• Cancer cells are destroyed.

Transparent plates of small size, not containing nuclei. These are particles of megakaryocyte cells concentrated in the bone marrow.

Platelets can be:

• oval;
• spherical;
• rod-shaped.

They function up to 10 days, performing an important function in the body - participation in blood clotting.

Platelets secrete substances that are involved in reactions triggered by damage to blood vessels.

That is why fibrinogen is transformed into fibrin strands, where clots can form.

What are functional disorders platelets? Peripheral blood of an adult should contain 180 - 320 x 109 / l. Daily fluctuations are observed: in daytime the number of thrombocytes increases in relation to night. Their reduction in the body is called thrombocytopenia, and the increase is called thrombocytosis.

Thrombocytopenia occurs in the following cases:

1. The bone marrow produces few platelets, or if the platelets are rapidly destroyed.

The following can have a negative effect on the production of blood plates:

1. With thrombocytopenia, there is a predisposition to the occurrence of light bruises (hematomas), which are formed after minimal pressure on the skin covering or completely unreasonable.
2. Bleeding during minor trauma or surgery.
3. Significant blood loss during menstruation.

If there is at least one of these symptoms, there is a reason to immediately consult a doctor.

Thrombocytosis causes the opposite effect: an increase in platelets provokes the formation blood clots(blood clots) that clog blood vessels. This is quite unsafe, as it can provoke a heart attack, stroke, or thrombophlebitis of the extremities (usually the lower ones).

In certain cases, platelets, even when they normal amount, unable to fully function and therefore provoke increased bleeding. Such pathologies of platelet function are congenital and acquired. This group also includes pathologies that were provoked long-term use medical preparations: for example, unjustified frequent use painkillers containing analgin.

Summary

The blood contains liquid plasma and formed elements - suspended cells. Timely detection of a changed percentage of blood composition provides an opportunity to detect the disease in the initial period.

Video - what is blood made of

Blood is a liquid substance in the human body that performs transport functions for oxygen and nutrients from the intestines to all organs and systems of the body. Also excreted through the blood toxic substances and exchange products. Blood provides a person with normal life and life in general.

Composition of blood and a brief description of the constituent elements

The blood is well studied. Today, according to its composition, doctors easily determine the state of human health and possible diseases.

Blood consists of plasma (the liquid part) and three dense groups of elements: erythrocytes, leukocytes and platelets. normal composition blood contains approximately 40-45% of dense elements. An increase in this indicator leads to a thickening of the blood, and a decrease to a thinning. An increase in the density / density of the blood occurs due to a large loss of fluid by the body, for example, due to diarrhea, with profuse sweating and so on. Liquefaction occurs, on the contrary, due to fluid retention in the body and when plentiful drink(in the case when the kidneys do not have time to remove excess water).

What is blood plasma made of?

The blood plasma contains up to 92% water, the rest is fats, proteins, carbohydrates, minerals and vitamins.

Proteins in the plasma provide normal blood clotting, transfer various substances from one organ to another, support various biochemical reactions of the body.

What proteins are in the blood plasma?

• albumins (they are the main building material for amino acids, keep blood inside the vessels, carry some substances);
• globulins (divided into three groups, two of them carry various substances, the third is involved in the formation of blood groups);
• fibrinogens (take part in the process of blood clotting).

In addition to proteins, amino acid residues in the form of nitrogenous compounds, chains, can still be present in the blood plasma. Also in the plasma there are still some substances that should not exceed certain indicators. Otherwise, with an increase in indicators, a violation of the excretory functions of the kidneys is diagnosed.

Other organic compounds in plasma, these are glucose, enzymes and lipids.

Dense elements of human blood

Erythrocytes are cells without a nucleus. The description was given in a previous article.

Leukocytes are responsible for. The task of leukocytes is to capture and neutralize infectious elements, as well as to create a database that is passed on to subsequent generations. Thus, either illnesses or immunity are transmitted from parents to children.

Platelets provide blood to bloodstream. The peculiarity of these cells is that they do not have a nucleus, like erythrocytes, and they are able to stick anywhere. It is they who provide blood clotting in case of damage to blood vessels and skin, creating thrombotic seals and not allowing blood to leak out.

For normal functioning human body as a whole, it is necessary to have a connection between all its organs. Critical importance in this respect has the circulation of fluids in the body, primarily blood and lymph. Blood transports hormones and biologically active substances involved in the regulation of body activity. In the blood and lymph are special cages performing protective functions. Finally, these fluids play important role in maintaining physical and chemical properties the internal environment of the body, which ensures the existence of body cells in a relatively constant conditions and reduce the influence of the external environment on them.

Blood consists of plasma and formed elements - blood cells. The latter include erythrocytes- red blood cells leukocytes- white blood cells and platelets- platelets (Fig. 1). Total blood in an adult - 4-6 liters (about 7% of body weight). Men have slightly more blood - an average of 5.4 liters, women - 4.5 liters. Loss of 30% of blood is dangerous, 50% is fatal.

Plasma
Plasma is liquid part blood, 90-93% water. Essentially, plasma is intercellular substance liquid consistency. Plasma contains 6.5-8% proteins, another 2-3.5% are other organic and inorganic compounds. Plasma proteins, albumins and globulins, perform trophic, transport, protective function, participate in blood coagulation and create a certain osmotic pressure of the blood. Plasma contains glucose (0.1%), amino acids, urea, uric acid, lipids. inorganic substances make up less than 1% (ions Na, K, Mg, Ca, Cl, P, etc.).

Erythrocytes (from the Greek. erythros- red) - highly specialized cells designed to transport gaseous substances. Erythrocytes have the form of biconcave discs with a diameter of 7-10 microns, a thickness of 2-2.5 microns. This shape increases the surface for diffusion of gases, and also makes the erythrocyte easily deformable when moving through narrow tortuous capillaries. Erythrocytes do not have a nucleus. They contain protein hemoglobin, through which the transport of respiratory gases is carried out. The non-protein part of hemoglobin (heme) has an iron ion.

In the capillaries of the lungs, hemoglobin forms an unstable compound with oxygen - oxyhemoglobin (Fig. 2). Blood saturated with oxygen is called arterial blood and has a bright scarlet color. This blood is delivered through the vessels to each cell human body. Oxyhemoglobin gives oxygen to tissue cells and combines with the incoming from them carbon dioxide. Blood that is poor in oxygen dark color and is called venous. By vascular system deoxygenated blood from organs and tissues is delivered to the lungs, where it is again saturated with oxygen.

In adults, red blood cells are formed in the red bone marrow, which is located in the cancellous bone. 1 liter of blood contains 4.0-5.0×1012 erythrocytes. The total number of erythrocytes in an adult reaches 25×1012, and the surface area of ​​all erythrocytes is about 3800 m2. With a decrease in the number of erythrocytes in the blood or a decrease in the amount of hemoglobin in erythrocytes, the supply of tissues with oxygen is disrupted and anemia develops - anemia (see Fig. 2).

The duration of circulation of red blood cells in the blood is about 120 days, after which they are destroyed in the spleen and liver. The tissues of other organs are also capable of destroying red blood cells if necessary, as evidenced by the gradual disappearance of hemorrhages (bruises).

Leukocytes
Leukocytes (from the Greek. leukos- white) - cells with a nucleus of 10-15 microns in size, which can move independently. Leukocytes contain a large number of enzymes that can break down various substances. Unlike erythrocytes, which work while inside the blood vessels, leukocytes perform their functions directly in the tissues, where they enter through the intercellular gaps in the vessel wall. 1 liter of blood of an adult contains 4.0-9.0´109 leukocytes, the number may vary depending on the state of the organism.

There are several types of leukocytes. to the so-called granular leukocytes include neutrophilic, eosinophilic and basophilic leukocytes, non-granular- lymphocytes and monocytes. Leukocytes are formed in the red bone marrow, and non-granular leukocytes are also formed in lymph nodes, spleen, tonsils, thymus ( thymus). The life span of most leukocytes is from several hours to several months.

Neutrophilic leukocytes (neutrophils) make up 95% of granular leukocytes. They circulate in the blood for no more than 8-12 hours, and then migrate to the tissues. Neutrophils destroy bacteria and tissue breakdown products with their enzymes. The famous Russian scientist I.I. Mechnikov called the phenomenon of destruction of foreign bodies by leukocytes phagocytosis, and the leukocytes themselves - phagocytes. During phagocytosis, neutrophils die, and the enzymes they secrete destroy surrounding tissues, contributing to the formation of an abscess. Pus consists mainly of neutrophil residues and tissue breakdown products. The number of neutrophils in the blood increases sharply in acute inflammatory and infectious diseases.

Eosinophilic leukocytes (eosinophils)- This is about 5% of all leukocytes. Especially a lot of eosinophils in the intestinal mucosa and respiratory tract. These leukocytes are involved in the immune (defensive) reactions of the body. The number of eosinophils in the blood increases with helminthic infestations and allergic reactions.

Basophilic leukocytes make up about 1% of all leukocytes. Basophils produce biologically active substances heparin and histamine. Heparin of basophils prevents blood clotting in the focus of inflammation, and histamine dilates capillaries, which contributes to the processes of resorption and healing. Basophils also carry out phagocytosis and are involved in allergic reactions.

The number of lymphocytes reaches 25-40% of all leukocytes, but they prevail in the lymph. There are T-lymphocytes (formed in the thymus) and B-lymphocytes (formed in the red bone marrow). Lymphocytes perform important features in immune responses.

Monocytes (1-8% of leukocytes) stay in the circulatory system for 2-3 days, after which they migrate to tissues, where they turn into macrophages and perform their main function- protection of the body from foreign substances (participate in immune reactions).

platelets
Platelets are small bodies various shapes, 2-3 microns in size. Their number reaches 180.0-320.0´109 per 1 liter of blood. Platelets are involved in blood clotting and stopping bleeding. The life span of platelets is 5-8 days, after which they enter the spleen and lungs, where they are destroyed.

The most important defense mechanism protecting the body from blood loss. This is a stop of bleeding by the formation of a blood clot (thrombus), tightly clogging the hole in the damaged vessel. At healthy person bleeding on injury small vessels stops within 1-3 minutes. When the wall is damaged blood vessel platelets stick together and stick to the edges of the wound, biologically active substances are released from the platelets, which cause vasoconstriction.

With more significant damage, bleeding stops as a result of a complex multi-stage process of enzymatic chain reactions. Under the influence external causes in damaged vessels, blood coagulation factors are activated: the plasma protein prothrombin, which is formed in the liver, turns into thrombin, which, in turn, causes the formation of insoluble fibrin from the soluble plasma protein fibrinogen. Fibrin threads form the main part of a thrombus, in which numerous blood cells get stuck (Fig. 3). The resulting thrombus clogs the injury site. Blood clotting occurs in 3-8 minutes, however, with some diseases, this time may increase or decrease.

Blood types

Of practical interest is the knowledge of blood group. The division into groups is based on different types combinations of erythrocyte antigens and plasma antibodies, which are a hereditary trait of blood and are formed on early stages body development.

It is customary to distinguish four main blood groups according to the AB0 system: 0 (I), A (II), B (III) and AB (IV), which is taken into account when it is transfused. In the middle of the 20th century, it was assumed that the blood of the 0 (I) Rh- group was compatible with any other groups. People with 0(I) blood group were considered universal donors, and their blood could be transfused to anyone in need, and they themselves - only blood of group I. People with IV blood group were considered universal recipients, they were injected with blood of any group, but their blood was given only to people with IV group.

Now in Russia vital indications and in the absence of blood components of the same group according to the AB0 system (with the exception of children), transfusion is allowed Rh negative blood 0(I) group to the recipient with any other blood group in an amount up to 500 ml. In the absence of single-group plasma, the recipient may be transfused with group AB(IV) plasma.

If the blood types of the donor and the recipient do not match, the erythrocytes of the transfused blood stick together and their subsequent destruction, which can lead to the death of the recipient.

In February 2012, US scientists, in collaboration with Japanese and French colleagues, discovered two new "additional" blood types, including two proteins on the surface of red blood cells - ABCB6 and ABCG2. They belong to transport proteins - they are involved in the transfer of metabolites, ions inside and out of the cell.

To date, more than 250 blood group antigens are known, combined into 28 additional systems in accordance with the patterns of their inheritance, most of which are much less common than AB0 and Rh factor.

Rh factor

When transfusing blood, the Rh factor (Rh factor) is also taken into account. Like blood groups, it was discovered by the Viennese scientist K. Landsteiner. This factor has 85% of people, their blood is Rh-positive (Rh +); others do not have this factor, their blood is Rh-negative (Rh-). Severe consequences has a blood transfusion from an Rh+ donor to a person with Rh-. The Rh factor is important for the health of the newborn and repeated pregnancy Rh-negative woman from an Rh-positive man.

Lymph

Lymph drains from tissues lymphatic vessels, which is part of cardio-vascular system. Lymph is similar in composition to blood plasma, but contains fewer proteins. Lymph is formed from tissue fluid, which, in turn, arises due to the filtration of blood plasma from the blood capillaries.

Blood test

The blood test is of great diagnostic value. The study of the blood picture is carried out according to many indicators, including the number of blood cells, the level of hemoglobin, the content various substances in plasma, etc. Each indicator, taken separately, is not specific in itself, but receives a certain value only in conjunction with other indicators and in connection with clinical picture diseases. That is why every person repeatedly donates a drop of his blood for analysis during his life. Modern methods studies allow, based on the study of this drop alone, to understand a lot in the state of human health.