What is the blood called. Thrombocytopenias happen in cases. Capillaries push out dead blood cells

1. Blood - This is a liquid tissue circulating through the vessels, transporting various substances within the body and providing nutrition and metabolism of all body cells. The red color of blood is due to hemoglobin contained in erythrocytes.

In multicellular organisms, most cells do not have direct contact with the external environment; their vital activity is ensured by the presence internal environment(blood, lymph, tissue fluid). From it they receive the substances necessary for life and secrete metabolic products into it. The internal environment of the body is characterized by a relative dynamic constancy of composition and physical and chemical properties which is called homeostasis. The morphological substrate that regulates metabolic processes between blood and tissues and maintains homeostasis are histo-hematic barriers consisting of capillary endothelium, basement membrane, connective tissue, and cellular lipoprotein membranes.

The concept of "blood system" includes: blood, hematopoietic organs (red bone marrow, lymph nodes, etc.), organs of blood destruction and regulatory mechanisms (regulating neurohumoral apparatus). The blood system is one of critical systems life support of the body and performs many functions. Cardiac arrest and cessation of blood flow immediately leads the body to death.

Physiological functions of blood:

4) thermoregulatory - regulation of body temperature by cooling energy-intensive organs and warming organs that lose heat;

5) homeostatic - maintaining the stability of a number of homeostasis constants: pH, osmotic pressure, isoionic, etc.;

Leukocytes perform many functions:

1) protective - the fight against foreign agents; they phagocytize (absorb) foreign bodies and destroy them;

2) antitoxic - the production of antitoxins that neutralize the waste products of microbes;

3) the production of antibodies that provide immunity, i.e. immunity to infectious diseases;

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

5) enzymatic - they contain various enzymes necessary for the implementation of phagocytosis;

6) participate in the processes of blood coagulation and fibrinolysis by producing heparin, gnetamine, plasminogen activator, etc.;

7) are the central link of the body's immune system, performing the function of immune surveillance ("censorship"), protecting against everything foreign and maintaining genetic homeostasis (T-lymphocytes);

8) provide transplant rejection reaction, destruction of own mutant cells;

9) form active (endogenous) pyrogens and form a feverish reaction;

10) carry macromolecules with the information necessary to control the genetic apparatus of other body cells; through such intercellular interactions (creator connections), the integrity of the organism is restored and maintained.

4 . Platelet or a platelet, a shaped element involved in blood coagulation, necessary to maintain the integrity of the vascular wall. It is a round or oval non-nuclear formation with a diameter of 2-5 microns. Platelets form in red bone marrow from giant cells - megakaryocytes. In 1 μl (mm 3) of human blood, 180-320 thousand platelets are normally contained. An increase in the number of platelets in the peripheral blood is called thrombocytosis, a decrease is called thrombocytopenia. The life span of platelets is 2-10 days.

The main physiological properties of platelets are:

1) amoeboid mobility due to the formation of prolegs;

2) phagocytosis, i.e. absorption foreign bodies and microbes;

3) sticking to a foreign surface and gluing together, while they form 2-10 processes, due to which attachment occurs;

4) easy destructibility;

5) release and absorption of various biologically active substances such as serotonin, adrenaline, norepinephrine, etc.;

All these properties of platelets determine their participation in stopping bleeding.

Platelet Functions:

1) actively participate in the process of blood coagulation and dissolution of a blood clot (fibrinolysis);

2) participate in stopping bleeding (hemostasis) due to the biologically active compounds present in them;

3) perform a protective function due to agglutination of microbes and phagocytosis;

4) produce some enzymes (amylolytic, proteolytic, etc.) necessary for the normal functioning of platelets and for the process of stopping bleeding;

5) influence the state of histohematic barriers between blood and tissue fluid by changing the permeability of capillary walls;

6) carry out the transport of creative substances that are important for maintaining the structure of the vascular wall; Without interaction with platelets, the vascular endothelium undergoes dystrophy and begins to let red blood cells through itself.

Rate (reaction) of erythrocyte sedimentation(abbreviated as ESR) - an indicator that reflects changes in the physicochemical properties of blood and the measured value of the plasma column released from erythrocytes when they settle from a citrate mixture (5% sodium citrate solution) for 1 hour in a special pipette of the device T.P. Panchenkov.

AT ESR norm is equal to:

In men - 1-10 mm / hour;

In women - 2-15 mm / hour;

Newborns - from 2 to 4 mm / h;

Children of the first year of life - from 3 to 10 mm / h;

Children aged 1-5 years - from 5 to 11 mm / h;

Children 6-14 years old - from 4 to 12 mm / h;

Over 14 years old - for girls - from 2 to 15 mm / h, and for boys - from 1 to 10 mm / h.

in pregnant women before childbirth - 40-50 mm / hour.

An increase in ESR more than the indicated values ​​is, as a rule, a sign of pathology. The ESR value does not depend on the properties of erythrocytes, but on the properties of plasma, primarily on the content of large molecular proteins in it - globulins and especially fibrinogen. The concentration of these proteins increases in all inflammatory processes. During pregnancy, the content of fibrinogen before childbirth is almost 2 times higher than normal, so the ESR reaches 40-50 mm/hour.

Leukocytes have their own settling regime independent of erythrocytes. However, the leukocyte sedimentation rate in the clinic is not taken into account.

Hemostasis (Greek haime - blood, stasis - immobile state) is the stoppage of the movement of blood through a blood vessel, i.e. stop bleeding.

There are 2 mechanisms to stop bleeding:

1) vascular-platelet (microcirculatory) hemostasis;

2) coagulation hemostasis (blood clotting).

The first mechanism is capable of independently stopping bleeding from the most frequently injured small vessels with rather low blood pressure in a few minutes.

It consists of two processes:

1) vascular spasm, leading to a temporary stop or decrease in bleeding;

2) formation, compaction and reduction of platelet plug, leading to a complete stop of bleeding.

The second mechanism for stopping bleeding - blood coagulation (hemocoagulation) ensures the cessation of blood loss in case of damage to large vessels, mainly of the muscular type.

It is carried out in three phases:

I phase - the formation of prothrombinase;

Phase II - the formation of thrombin;

Phase III - the transformation of fibrinogen into fibrin.

In the mechanism of blood coagulation, in addition to the wall blood vessels and shaped elements, 15 plasma factors take part: fibrinogen, prothrombin, tissue thromboplastin, calcium, proaccelerin, convertin, antihemophilic globulins A and B, fibrin-stabilizing factor, prekallikrein (Fletcher factor), high-molecular kininogen (Fitzgerald factor), etc.

Most of these factors are formed in the liver with the participation of vitamin K and are proenzymes related to the globulin fraction of plasma proteins. AT active form- enzymes they pass in the process of coagulation. Moreover, each reaction is catalyzed by an enzyme formed as a result of the previous reaction.

The trigger for blood clotting is the release of thromboplastin by damaged tissue and decaying platelets. Calcium ions are necessary for the implementation of all phases of the coagulation process.

A blood clot is formed by a network of insoluble fibrin fibers and entangled erythrocytes, leukocytes and platelets. The strength of the formed blood clot is provided by factor XIII, a fibrin-stabilizing factor (fibrinase enzyme synthesized in the liver). Blood plasma devoid of fibrinogen and some other substances involved in coagulation is called serum. And the blood from which fibrin is removed is called defibrinated.

The time of complete clotting of capillary blood is normally 3-5 minutes, venous blood - 5-10 minutes.

In addition to the coagulation system, there are two more systems in the body at the same time: anticoagulant and fibrinolytic.

The anticoagulant system interferes with the processes of intravascular blood coagulation or slows down hemocoagulation. The main anticoagulant of this system is heparin, secreted from lung and liver tissues and produced by basophilic leukocytes and tissue basophils ( mast cells connective tissue). The number of basophilic leukocytes is very small, but all tissue basophils of the body have a mass of 1.5 kg. Heparin inhibits all phases of the blood coagulation process, inhibits the activity of many plasma factors and the dynamic transformation of platelets. Secreted by the salivary glands medicinal leeches gi-rudin has a depressing effect on the third stage of the blood coagulation process, i.e. prevents the formation of fibrin.

The fibrinolytic system is able to dissolve the formed fibrin and blood clots and is the antipode of the coagulation system. The main function of fibrinolysis is the splitting of fibrin and the restoration of the lumen of a vessel clogged with a clot. Cleavage of fibrin is carried out by the proteolytic enzyme plasmin (fibrinolysin), which is present in plasma as the proenzyme plasminogen. For its transformation into plasmin, there are activators contained in the blood and tissues, and inhibitors (Latin inhibere - restrain, stop) that inhibit the transformation of plasminogen into plasmin.

Violation of the functional relationships between the coagulation, anticoagulation and fibrinolytic systems can lead to serious diseases: increased bleeding, intravascular thrombosis and even embolism.

Blood types- a set of features that characterize the antigenic structure of erythrocytes and the specificity of anti-erythrocyte antibodies, which are taken into account when selecting blood for transfusions (lat. transfusio - transfusion).

In 1901, the Austrian K. Landsteiner and in 1903 the Czech J. Jansky discovered that when the blood of different people is mixed, erythrocytes often stick together - the phenomenon of agglutination (Latin agglutinatio - gluing) with their subsequent destruction (hemolysis ). It was found that erythrocytes contain agglutinogens A and B, glued substances of a glycolipid structure, and antigens. In plasma, agglutinins α and β, modified proteins of the globulin fraction, antibodies that stick together erythrocytes were found.

Agglutinogens A and B in erythrocytes, as well as agglutinins α and β in plasma, may be present alone or together, or absent in different people. Agglutinogen A and agglutinin α, as well as B and β are called of the same name. Bonding of erythrocytes occurs if the erythrocytes of the donor (of the person giving blood) meet with the same agglutinins of the recipient (of the person receiving blood), i.e. A + α, B + β or AB + αβ. From this it is clear that in the blood of each person there are opposite agglutinogen and agglutinin.

According to the classification of J. Jansky and K. Landsteiner, people have 4 combinations of agglutinogens and agglutinins, which are designated as follows: I (0) - αβ., II (A) - A β, W (V) - B α and IV(AB). From these designations it follows that in people of group 1, agglutinogens A and B are absent in erythrocytes, and both α and β agglutinins are present in plasma. In people of group II, erythrocytes have agglutinogen A, and plasma - agglutinin β. Group III includes people who have agglutinogen B in their erythrocytes, and agglutinin α in plasma. In people of group IV, erythrocytes contain both agglutinogens A and B, and there are no agglutinins in plasma. Based on this, it is not difficult to imagine which groups can be transfused with the blood of a certain group (Scheme 24).

As can be seen from the diagram, people of group I can only receive blood from this group. The blood of group I can be transfused to people of all groups. Therefore, people with blood group I are called universal donors. People with group IV can be transfused with blood of all groups, so these people are called universal recipients. Group IV blood can be transfused to people with group IV blood. The blood of people of II and III groups can be transfused to people with the same name, as well as with IV blood group.

However, at present in clinical practice transfuse only one-group blood, and not in large quantities(not more than 500 ml), or the missing blood components are transfused (component therapy). This is due to the fact that:

firstly, during large massive transfusions, the donor agglutinins do not dilute, and they stick together the recipient's erythrocytes;

secondly, with a careful study of people with blood of group I, immune agglutinins anti-A and anti-B were found (in 10-20% of people); transfusion of such blood to people with other blood types causes severe complications. Therefore, people with blood group I, containing anti-A and anti-B agglutinins, are now called dangerous universal donors;

thirdly, many variants of each agglutinogen were revealed in the ABO system. Thus, agglutinogen A exists in more than 10 variants. The difference between them is that A1 is the strongest, while A2-A7 and other variants have weak agglutination properties. Therefore, the blood of such individuals can be erroneously assigned to group I, which can lead to blood transfusion complications when it is transfused to patients with groups I and III. Agglutinogen B also exists in several variants, the activity of which decreases in the order of their numbering.

In 1930, K. Landsteiner, speaking at the Nobel Prize ceremony for the discovery of blood groups, suggested that new agglutinogens would be discovered in the future, and the number of blood groups would grow until it reached the number of people living on earth . This assumption of the scientist turned out to be correct. To date, more than 500 different agglutinogens have been found in human erythrocytes. Only from these agglutinogens, more than 400 million combinations, or group signs of blood, can be made.

If we take into account all the other agglutinogens found in the blood, then the number of combinations will reach 700 billion, i.e. significantly more than people on the globe. This determines the amazing antigenic uniqueness, and in this sense, each person has his own blood type. These agglutinogen systems differ from the ABO system in that they do not contain natural agglutinins in plasma, similar to α- and β-agglutinins. But under certain conditions, immune antibodies - agglutinins - can be produced to these agglutinogens. Therefore, it is not recommended to repeatedly transfuse a patient with blood from the same donor.

To determine blood groups, you need to have standard sera containing known agglutinins, or anti-A and anti-B coliclones containing diagnostic monoclonal antibodies. If you mix a drop of blood of a person whose group needs to be determined with the serum of groups I, II, III or with anti-A and anti-B coliclones, then by the onset of agglutination, you can determine his group.

Despite the simplicity of the method, in 7-10% of cases, the blood group is determined incorrectly, and incompatible blood is administered to patients.

To avoid such a complication, before a blood transfusion, it is necessary to carry out:

1) determination of the blood group of the donor and recipient;

2) Rh-affiliation of the blood of the donor and recipient;

3) test for individual compatibility;

4) a biological test for compatibility during transfusion: first, 10-15 ml of donor blood is poured in and then the patient's condition is monitored for 3-5 minutes.

Transfused blood always acts in many ways. In clinical practice, there are:

1) replacement action - replacement of lost blood;

2) immunostimulating effect - in order to stimulate the protective forces;

3) hemostatic (hemostatic) action - in order to stop bleeding, especially internal;

4) neutralizing (detoxifying) action - in order to reduce intoxication;

5) nutritional action - the introduction of proteins, fats, carbohydrates in an easily digestible form.

in addition to the main agglutinogens A and B, there may be other additional ones in erythrocytes, in particular the so-called Rh agglutinogen (Rhesus factor). It was first found in 1940 by K. Landsteiner and I. Wiener in the blood of a rhesus monkey. 85% of people have the same Rh agglutinogen in their blood. Such blood is called Rh-positive. Blood that lacks Rh agglutinogen is called Rh negative (in 15% of people). The Rh system has more than 40 varieties of agglutinogens - O, C, E, of which O is the most active.

A feature of the Rh factor is that people do not have anti-Rh agglutinins. However, if a person with Rh-negative blood is re-transfused with Rh-positive blood, then under the influence of the injected Rh agglutinogen, specific anti-Rh agglutinins and hemolysins are produced in the blood. In this case, transfusion of Rh-positive blood to this person can cause agglutination and hemolysis of red blood cells - there will be a hemotransfusion shock.

The Rh factor is inherited and is of particular importance for the course of pregnancy. For example, if the mother does not have an Rh factor, and the father does (the probability of such a marriage is 50%), then the fetus can inherit the Rh factor from the father and turn out to be Rh-positive. The blood of the fetus enters the mother's body, causing the formation of anti-Rh agglutinins in her blood. If these antibodies pass through the placenta back into the fetal blood, agglutination will occur. With a high concentration of anti-Rh agglutinins, fetal death and miscarriage can occur. In mild forms of Rh incompatibility, the fetus is born alive, but with hemolytic jaundice.

Rhesus conflict occurs only with a high concentration of anti-Rh gglutinins. Most often, the first child is born normal, since the titer of these antibodies in the mother's blood increases relatively slowly (over several months). But at repeated pregnancy For an Rh-negative woman with an Rh-positive fetus, the threat of an Rh conflict increases due to the formation of new portions of anti-Rh agglutinins. Rh incompatibility during pregnancy is not very common: about one in 700 births.

To prevent Rh conflict, pregnant Rh-negative women are prescribed anti-Rh-gamma globulin, which neutralizes the Rh-positive antigens of the fetus.

The center of the circulatory system is the heart, which acts as two pumps. The right side of the heart (venous) promotes blood in the pulmonary circulation, the left (arterial) - in a large circle. The pulmonary circulation begins from the right ventricle of the heart, then venous blood enters the pulmonary trunk, which is divided into two pulmonary arteries, which are divided into smaller arteries that pass into the capillaries of the alveoli, in which gas exchange occurs (blood gives off carbon dioxide and is enriched with oxygen). Two veins emerge from each lung and empty into the left atrium. big circle blood circulation starts from the left ventricle of the heart. Arterial blood enriched with oxygen and nutrients enters all organs and tissues, where gas exchange and metabolism take place. Taking carbon dioxide and decay products from the tissues, venous blood collects in the veins and moves to the right atrium.
By circulatory system blood moves, which is arterial (saturated with oxygen) and venous (saturated with carbon dioxide).
There are three types of blood vessels in humans: arteries, veins, and capillaries. Arteries and veins differ from each other in the direction of blood flow in them. Thus, an artery is any vessel that carries blood from the heart to an organ, and a vein is a blood carrier from an organ to the heart, regardless of the composition of the blood (arterial or venous) in them. Capillaries are the thinnest vessels, they are 15 times thinner than a human hair. The walls of the capillaries are semi-permeable, through which substances dissolved in the blood plasma seep into the tissue fluid, from which they pass into the cells. The products of cell metabolism penetrate in the opposite direction from the tissue fluid into the blood.
Blood moves through the vessels from the heart under the influence of pressure created by the heart muscle at the time of its contraction. The return flow of blood through the veins is influenced by several factors:
- firstly, venous blood moves towards the heart under the action of skeletal muscle contractions, which, as it were, push blood out of the veins towards the heart, while the reverse movement of blood is excluded, since the valves in the veins pass blood in only one direction - to heart.
The mechanism of forced movement of venous blood to the heart with overcoming the forces of gravity under the influence of rhythmic contractions and relaxation of skeletal muscles is called a muscle pump.
Thus, during cyclic movements, skeletal muscles significantly help the heart to circulate blood in the vascular system;
- secondly, when inhaling, the chest expands and a reduced pressure is created in it, which ensures the suction of venous blood to the thoracic region;
- thirdly, at the moment of systole (contraction) of the heart muscle, when the atria relax, a suction effect also occurs in them, contributing to the movement of venous blood to the heart.
The heart is the central organ of the circulatory system. The heart is a hollow four-chambered muscular organ located in chest cavity, divided by a vertical partition into two halves - left and right, each of which consists of a ventricle and an atrium. The heart works automatically under the control of the central nervous system.
The wave of oscillations propagating along the elastic walls of the arteries as a result of the hydrodynamic impact of a portion of blood ejected into the aorta during the contraction of the left ventricle is called the heart rate (HR).
The heart rate of an adult male at rest is 65-75 beats / min., in women it is 8-10 beats more than in men. In trained athletes, heart rate at rest becomes less frequent due to an increase in the power of each heartbeat and can reach 40-50 beats / min.
The amount of blood pushed out by the ventricle of the heart into the vascular bed during one contraction is called the systolic (shock) blood volume. At rest, it is 60 ml for untrained people, and 80 ml for trained people. During physical exertion, in untrained people it increases to 100-130 ml, and in trained people up to 180-200 ml.
The amount of blood ejected from one ventricle of the heart in one minute is called the minute volume of blood. At rest, this figure is on average 4-6 liters. With physical exertion, it rises in untrained people to 18-20 liters, and in trained people up to 30-40 liters.
With each contraction of the heart, the blood entering the circulatory system creates pressure in it, which depends on the elasticity of the walls of the vessels. Its value at the time of cardiac contraction (systole) in young people is 115-125 mm Hg. Art. The minimum (diastolic) pressure at the moment of relaxation of the heart muscle is 60-80 mm Hg. Art. The difference between the maximum and minimum pressure is called pulse pressure. It is approximately 30-50 mm Hg. Art.
Under the influence of physical training, the size and mass of the heart increase due to the thickening of the walls of the heart muscle and an increase in its volume. The muscle of a trained heart is more densely permeated with blood vessels, which provides better nutrition. muscle tissue and its performance.

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

The composition of human blood plasma and its functions

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

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

Organic substances of blood plasma: what part are proteins

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

The main functions of blood plasma proteins:

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

Albumins, globulins and fibrinogen in blood plasma

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

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

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

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

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

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

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

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

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

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

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

Formed elements in blood plasma

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

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

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

Red blood cells in human blood: shape and composition

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

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

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

The structure and functions of erythrocytes in the human body

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

The main functions of erythrocytes in the blood:

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

The structure of the blood system: types of hemoglobin

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

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

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

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

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

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

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

Erythropoiesis - what is it?

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

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

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

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

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

How is erythropoiesis regulated and what stimulates it?

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

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

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

Erythrocytosis and its types

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

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

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

Types and composition of leukocytes in the blood

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

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

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

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

Details about each type of leukocytes and their functions - in next section articles.

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

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

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

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

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

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

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

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

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

Depending on the functions performed, they differ:

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

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

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

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

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

Leukocytosis and leukopenia of the blood

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

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

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

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

What is the function of platelets in the blood

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

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

The main functions of platelets in the blood:

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

Dysfunction of platelets in the blood

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

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

With a platelet disorder such as thrombocytopenia, there is a tendency to easy education bruises (hematomas) that occur with slight pressure or no reason at all; bleeding with minor injuries and operations (tooth extraction); in women - profuse blood loss during menstruation. If you notice at least one of these symptoms, you should consult a doctor and perform a blood test.

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

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

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

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 of 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.

Approximately 4 to 5 liters of blood circulate in the circulatory system of an adult. 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. Important role released 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, plasma contains hormones that are produced by endocrine glands, 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.

Red blood cells are produced in the 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. A person needs blood to maintain a constant body temperature, the norm of which is in a very narrow range - about 37 ° C.