The first school lessons on the structure of the human body introduce the main “inhabitants of the blood: red cells - erythrocytes (Er, RBC), which determine the color due to the content they contain, and white (leukocytes), the presence of which is not visible to the eye, because they do not affect.

Human erythrocytes, unlike animals, do not have a nucleus, but before losing it, they must go from the erythroblast cell, where hemoglobin synthesis just begins, reach the last nuclear stage - accumulating hemoglobin, and turn into a mature nuclear-free cell, the main component of which is the red blood pigment.

What people didn’t do with erythrocytes, studying their properties: they tried to wrap them around the globe (it turned out 4 times), and put them in coin columns (52 thousand kilometers), and compare the area of ​​erythrocytes with the surface area of ​​the human body (erythrocytes exceeded all expectations , their area turned out to be 1.5 thousand times higher).

These unique cells...

Another important feature of erythrocytes is their biconcave shape, but if they were spherical, then their total surface area would be 20% less than the real one. However, the ability of erythrocytes lies not only in the size of their total area. Due to the biconcave disc shape:

1. Red blood cells are able to carry more oxygen and carbon dioxide;
2. Show plasticity and freely pass through narrow holes and curved capillary vessels, that is, there are practically no obstacles for young full-fledged cells in the bloodstream. The ability to penetrate into the most remote corners of the body is lost with the age of red blood cells, as well as in their pathological conditions, when their shape and size change. For example, spherocytes, sickle-shaped, weights and pears (poikilocytosis) do not have such high plasticity, macrocytes cannot crawl into narrow capillaries, and even more so, megalocytes (anisocytosis), therefore, the altered cells do not perform their tasks so flawlessly.

The chemical composition of Er is mainly represented by water (60%) and dry residue (40%), in which 90 - 95% is occupied by the red blood pigment -, and the remaining 5-10% are distributed between lipids (cholesterol, lecithin, cephalin), proteins, carbohydrates, salts (potassium, sodium, copper, iron, zinc) and, of course, enzymes (carbonic anhydrase, cholinesterase, glycolytic, etc.).

The cellular structures that we are used to marking in other cells (nucleus, chromosomes, vacuoles) are absent in Er as unnecessary. Red blood cells live up to 3 - 3.5 months, then grow old and with the help of erythropoietic factors that are released during cell destruction, they give the command that it is time to replace them with new ones - young and healthy.

The erythrocyte takes its beginning from the precursors, which, in turn, come from the stem cell. Red blood cells are reproduced, if everything is normal in the body, in the bone marrow of flat bones (skull, spine, sternum, ribs, pelvic bones). In cases where, for some reason, the bone marrow cannot produce them (tumor damage), erythrocytes “remember” that other organs (liver, thymus, spleen) were involved in intrauterine development and force the body to start erythropoiesis in forgotten places.

How many should be normal?

The total number of red blood cells contained in the body as a whole, and the concentration of red cells plying through the bloodstream are different concepts. The total number includes cells that have not yet left the bone marrow, went to the depot in case of unforeseen circumstances, or set sail to perform their immediate duties. The totality of all three populations of erythrocytes is called - erythron. Erythron contains from 25 x 10 12 /l (Tera / liter) to 30 x 10 12 /l red blood cells.

The rate of red blood cells in the blood of adults differs by gender, and in children, depending on age. Thus:

• The norm in women ranges from 3.8 - 4.5 x 10 12 / l, respectively, they also have less hemoglobin;
• What is a normal indicator for a woman is called mild anemia in men, since the lower and upper limits of the norm of red blood cells are noticeably higher: 4.4 x 5.0 x 10 12 / l (the same applies to hemoglobin);
• In children under one year old, the concentration of erythrocytes is constantly changing, therefore, for each month (in newborns - every day) there is its own norm. And if suddenly in the blood test the erythrocytes in a child of two weeks old are increased to 6.6 x 10 12 / l, then this cannot be regarded as a pathology, it’s just that newborns have such a norm (4.0 - 6.6 x 10 12 / l).
• Some fluctuations are observed after a year of life, but normal values ​​\u200b\u200bare not very different from those in adults. In adolescents 12-13 years old, the content of hemoglobin in erythrocytes and the level of erythrocytes themselves correspond to the norm of adults.

An increased number of red blood cells is called erythrocytosis, which can be absolute (true) and redistributive. Redistributive erythrocytosis is not a pathology and occurs when red blood cells are elevated under certain circumstances:

1. Stay in a mountainous area;
2. Active physical labor and sports;
3. Psycho-emotional arousal;
4. Dehydration (loss of body fluid through diarrhea, vomiting, etc.).

High levels of erythrocytes in the blood are a sign of pathology and true erythrocytosis if they are the result of increased formation of red blood cells caused by unlimited proliferation (reproduction) of the precursor cell and its differentiation into mature forms of erythrocytes ().

Decreased concentration of red blood cells is called erythropenia. It is observed with blood loss, inhibition of erythropoiesis, the breakdown of erythrocytes () under the influence of adverse factors. Low erythrocytes in the blood and reduced Hb content in erythrocytes is a sign.

What does the abbreviation mean?

Modern hematological analyzers, in addition to hemoglobin (HGB), low or high red blood cell count (RBC), (HCT) and other usual tests, can calculate other indicators that are indicated by the Latin abbreviation and are not at all clear to the reader:

In addition to all the listed advantages of erythrocytes, I would like to note one more thing:

Erythrocytes are considered a mirror reflecting the state of many organs. A kind of indicator that can "feel" problems or allows you to monitor the course of the pathological process is.

Big ship - big voyage

Why are red blood cells so important in the diagnosis of many pathological conditions? Their special role follows and is formed due to their unique capabilities, and so that the reader can imagine the true significance of erythrocytes, let's try to list their responsibilities in the body.

Truly, The functional tasks of red blood cells are wide and varied:

1. They transport oxygen to tissues (with the participation of hemoglobin).
2. They carry carbon dioxide (with the participation, in addition to hemoglobin, of the enzyme carbonic anhydrase and the ion exchanger Cl- / HCO 3).
3. They perform a protective function, as they are able to adsorb harmful substances and carry antibodies (immunoglobulins), components of the complementary system, formed immune complexes (At-Ag) on ​​their surface, as well as synthesize an antibacterial substance called erythrin.
4. Participate in the exchange and regulation of water-salt balance.
5. Provide nutrition to tissues (erythrocytes adsorb and carry amino acids).
6. They participate in maintaining informational links in the body due to the transfer of macromolecules that these links provide (creator function).
7. They contain thromboplastin, which leaves the cell when red blood cells are destroyed, which is a signal for the coagulation system to begin hypercoagulation and formation. In addition to thromboplastin, erythrocytes carry heparin, which prevents thrombosis. Thus, the active participation of erythrocytes in the process of blood coagulation is obvious.
8. Red blood cells are capable of suppressing high immunoreactivity (acting as suppressors), which can be used in the treatment of various tumor and autoimmune diseases.
9. They participate in the regulation of the production of new cells (erythropoiesis) by releasing erythropoietic factors from destroyed old erythrocytes.

Red blood cells are destroyed mainly in the liver and spleen with the formation of decay products (iron). By the way, if we consider each cell separately, then it will not be so red, rather, yellowish-red. Accumulating in huge millions of masses, they, thanks to the hemoglobin in them, become the way we used to see them - a rich red color.

Video: lesson on red blood cells and blood functions

Erythrocytes are one of the very important elements of the blood. Filling organs with oxygen (O 2) and removing carbon dioxide (CO 2) from them is the main function of the formed elements of the blood fluid.

Other properties of blood cells are also significant. Knowing what red blood cells are, how long they live, where other data are destroyed, allows a person to monitor health and correct it in time.

General definition of erythrocytes

If you look at blood under a scanning electron microscope, you can see what shape and size red blood cells have.

Human blood under a microscope

Healthy (intact) cells are small discs (7-8 microns), concave on both sides. They are also called red blood cells.

The number of erythrocytes in the blood fluid exceeds the level of leukocytes and platelets. One drop of human blood contains about 100 million of these cells.

A mature erythrocyte is covered with a membrane. It does not have a nucleus and organelles, except for the cytoskeleton. The inside of the cell is filled with a concentrated fluid (cytoplasm). It is rich in the pigment hemoglobin.

The chemical composition of the cell, in addition to hemoglobin, includes:

• Water;
• Lipids;
• Proteins;
• Carbohydrates;
• salt;
• Enzymes.

Hemoglobin is a protein made up of heme and globin. Heme contains iron atoms. Iron in hemoglobin, binding oxygen in the lungs, stains the blood in a light red color. It turns dark when oxygen is released into the tissues.

Blood cells have a large surface due to their shape. The increased plane of the cells improves the exchange of gases.

The red blood cell is elastic. The very small size of the erythrocyte and flexibility allow it to easily pass through the smallest vessels - capillaries (2-3 microns).

How long do erythrocytes live

The lifespan of erythrocytes is 120 days. During this time, they perform all their functions. Then they are destroyed. The place of death is the liver, spleen.

Red blood cells decompose faster if their shape changes. When bulges appear in them, echinocytes are formed, depressions - stomatocytes. Poikilocytosis (change in shape) leads to cell death. Disk shape pathology arises from damage to the cytoskeleton.

Video -blood functions. red blood cells

Where and how are they formed

The life path of erythrocytes begins in the red bone marrow of all human bones (up to the age of five).

In an adult, after 20 years, red blood cells are produced in:

• spine;
• Sternum;
• Ribs;
• Ilium.

Their formation takes place under the influence of erythropoietin, a renal hormone.

With age, erythropoiesis, that is, the process of formation of red blood cells, decreases.

The formation of a blood cell begins with a proerythroblast. As a result of repeated division, mature cells are created.

From the unit that forms the colony, the erythrocyte goes through the following stages:

1. Erythroblast.
2. Pronormocyte.
3. Normoblasts of different types.
4. Reticulocyte.
5. Normocyte.

The primordial cell has a nucleus, which first becomes smaller and then leaves the cell altogether. Its cytoplasm is gradually filled with hemoglobin.

If there are reticulocytes in the blood along with mature red blood cells, this is normal. Earlier types of red blood cells in the blood indicate pathology.

Functions of red blood cells

Red blood cells realize their main purpose in the body - they are carriers of respiratory gases - oxygen and carbon dioxide.

This process is carried out in a certain order:

In addition to gas exchange, shaped elements perform other functions:

Normally, each red blood cell in the bloodstream is a free cell in movement. With an increase in blood acidity pH and other negative factors, gluing of red blood cells occurs. Their bonding is called agglutination.

Such a reaction is possible and very dangerous when blood is transfused from one person to another. In this case, to prevent agglutination of red blood cells, you need to know the blood group of the patient and his donor.

The agglutination reaction served as the basis for dividing people's blood into four groups. They differ from each other by the combination of agglutinogens and agglutinins.

The following table will introduce the features of each blood group:

In determining the blood type, it is impossible to make mistakes in any case. Knowing the group affiliation of blood is especially important when it is transfused. Not everyone suits a certain person.

Extremely important! Before a blood transfusion, it is imperative to determine its compatibility. It is impossible to inject incompatible blood into a person. It's life-threatening.

With the introduction of incompatible blood, agglutination of red blood cells occurs. This occurs with this combination of agglutinogens and agglutinins: Aα, Bβ. In this case, the patient has signs of hemotransfusion shock.

They can be:

• Headache;
• Anxiety;
• Flushed face;
• low blood pressure;
• Rapid pulse;
• Chest tightness.

Agglutination ends with hemolysis, that is, the destruction of red blood cells occurs in the body.

A small amount of blood or red blood cells can be transfused as follows:

• Group I - into the blood II, III, IV;
• II group - in IV;
• Group III - in IV.

Important! If it becomes necessary to transfuse a large amount of fluid, only the blood of the same group is infused.

The number of red blood cells in the blood is determined during a laboratory analysis and counted in 1 mm 3 of blood.

Reference. For any disease, a clinical blood test is prescribed. It gives an idea of ​​the hemoglobin content, the level of erythrocytes and their sedimentation rate (ESR). Blood is given in the morning, on an empty stomach.

Normal hemoglobin value:

• In men - 130-160 units;
• In women - 120-140.

The presence of red pigment in excess of the norm may indicate:

1. Great physical activity;
2. Increased blood viscosity;
3. Loss of moisture.

The inhabitants of the highlands, lovers of frequent smoking, hemoglobin is also elevated. Low hemoglobin levels occur with anemia (anemia).

Number of non-core drives:

• In men (4.4 x 5.0 x 10 12 / l) - higher than in women;
• In women (3.8 - 4.5 x 10 12 / l.);
• Children have their own norms, which are determined by age.

A decrease in the number of red cells or its increase (erythrocytosis) show that disturbances are possible in the activity of the body.

So, with anemia, blood loss, a decrease in the rate of formation of red cells in the bone marrow, their rapid death, and an increased water content, the level of red blood cells decreases.

An increased number of red cells can be detected while taking certain medications, such as corticosteroids, diuretics. A consequence of insignificant erythrocytosis is a burn, diarrhea.

Erythrocytosis also occurs in conditions such as:

• Itsenko-Cushing syndrome (hypercorticism);
• Cancer formations;
• Polycystic kidney disease;
• Dropsy of the renal pelvis (hydronephrosis), etc.

Important! In pregnant women, normal blood cell counts change. This is most often associated with the birth of the fetus, the appearance of the child's own circulatory system, and not with the disease.

An indicator of a malfunction in the body is the erythrocyte sedimentation rate (ESR).

It is not recommended to make diagnoses on the basis of tests. Only a specialist after a thorough examination using various techniques can draw the right conclusions and prescribe an effective treatment.

Erythrocytes, or red blood cells, greatly outnumber white blood cells and blood platelets. In addition to the human body, they are present in all vertebrates and in some species of invertebrate living beings.

Where are cells grown?

Red blood cells are produced in the bones of the skull, bone marrow, spine, and ribs. In childhood, there is another place of synthesis - the ends of the long tubular bones of the legs and arms.

The destruction of aged red blood cells occurs in the liver and spleen. They live an average of 3 months. Any processes that disrupt the "production" or increase the destruction of red blood cells lead to disease.

Reticulocytes have fibrous structures inside

About 3% of reticulocytes are constantly present in the blood. These are precursor cells of maturing red blood cells. The presence of earlier "earlier" progenitors means pathology.

"Portrait" of a middle-aged erythrocyte

The size of the cells is determined by the diameter, it is 7.5 microns (micrometers). This is 6 times smaller than the thinnest human hair. The total surface of all erythrocytes is 1.5 thousand times greater than the covering of the human body. The change in size is called anisocytosis.

The shape of the cells is flat, with thickenings along the edges, forming a disc concave on both sides. The "design" of the cell is due to the optimal distance of each point of the surface to the center, this increases the possibilities in contact with the transported gas molecules. There is no nucleus inside the cell (fish, birds and amphibians have one), which is associated with an adaptation to bind more hemoglobin.

A disorder in the shape of blood cells is called poikilocytosis. Up to 15% of altered cells are allowed.

Erythrocytes do not synthesize their protein, 71% of the mass of the cell is water, 10% is the shell covered with a membrane. Cells economically feed on the energy received without oxygen.

In reticulocytes, the sizes are larger, inside there is a mesh formation containing amino acids and fats.

The plasma membrane is half composed of glycoproteins, it is able to pass through itself oxygen, carbon dioxide, electrolytes sodium and potassium, water. This suggests that a violation of the protein-lipid composition of the blood (cholesterol level) leads to premature wrinkling and destruction.

By weight, up to 90% is occupied by hemoglobin (a chemical compound of iron with protein).

Tasks and functions

The main functions of erythrocytes are related to:

• with the transfer of oxygen from the pulmonary lobules to the tissues, and carbon dioxide in the opposite direction;
• representation of the species antigenic specificity of human blood (the system for determining blood groups AB0 is based precisely on the properties of erythrocyte agglutinogens);
• with the support of the acid-base ratio (balance) and osmotic pressure necessary for the course of biological processes in the body;
• simultaneous transfer of fat-like organic acids into tissues.

RBCs carry oxygen molecules

What is considered normal

The total number of these cells in the body is determined by the number 25x10 12 . Laboratory calculation is carried out according to the content of cells in one cubic mm of blood.

According to the rules, the analysis is taken from capillary or venous blood in the morning after a quiet rest and before meals. The level of erythrocytes is influenced by external conditions, the nature of nutrition.

The norm changes throughout life. There is a dependence on the age of a person, gender and the climatic zone where people live.

In a child in the neonatal period, the maximum number of erythrocyte cells is observed (within 4.3 - 7.6 x 10¹² / l). The destruction of the mother's red blood cells immediately after birth and their replacement with their own causes yellowness of the skin. By the year, the amount decreases to 3.6 - 4.9 x 10¹² / l, and in adolescence it slightly increases to "adult" indicators (3.6 - 5.1 x 10¹² / l).

The level in women (3.7 - 4.7 x 10¹² /l) is lower than in men (4.0 - 5.1 x 10¹² /l). This is due to physiological blood loss during critical days. During pregnancy, a woman's body begins to increase the consumption of iron, and with it red blood cells. Mild anemia (anemia) indicates this feature.

A decrease in red blood cells is called anemia. The degree and form of the disease is influenced by different causes.

An increase in the number of red blood cells (erythrocytosis) is possible with significant dehydration or with blood pathology associated with increased synthesis of red blood cells, a violation of their utilization.

How does agglutination happen?

Agglutination of erythrocytes is a reaction of the interaction of agglutinogens (antigens) located on the surface of the cell membrane with specific plasma agglutinins. The result of the interaction can be seen when determining the blood type on a white plate - the formation of small sticky lumps.

In a healthy person, this process is reversible and is possible when the cells lose their electric charge. In pathological conditions, agglutination contributes to thrombosis. At the same time, the number of free red blood cells in the blood falls.

Below shows agglutination of red blood cells during slow blood flow.

How red blood cells are involved in respiration

Red blood cells are responsible for saturating the blood with oxygen and removing unnecessary accumulations of carbon dioxide. For this, most of the cell mass is occupied by hemoglobin (globin protein + 4 heme/iron molecules). It is called "blood pigment" because it is heme that provides the color of blood. Depending on the sequence of amino acids, different types of pigment are distinguished in globin.

The oxyhemoglobin complex is formed by combining with oxygen. It is created in the pulmonary capillaries, and in the tissues it breaks down again and gives free oxygen to the cells.

The appearance of methemoglobin or carboxyhemoglobin in the blood during poisoning and intoxication disrupts the process of oxygen transfer, leading to tissue hypoxia.

Erythrocyte sedimentation rate

Since erythrocytes have their own mass, the blood, when drawn into a graduated tube, is stratified due to cell settling. To prevent gluing of cellular elements, a special solution is added.

The result of the reaction is evaluated after an hour by the height of the transparent column.

The reaction in men is considered normal - from 12 to 32 mm / hour, in women - from 18 to 23. In pregnant women, the ESR rises to 60 - 70 mm / hour. The reaction is widely used in the diagnosis of diseases along with other tests.

RBC resistance

The ability to keep its shape and work steadily in the blood is called resistance. It is important to bear in mind that for this, the isotonic concentration of sodium chloride in the blood must be maintained.

1. With an increase in concentration (hypertonic solution), erythrocytes lose water, shrink, and are unable to carry oxygen.
2. In the case of blood thinning and hypotonic concentration, water tends to enter the blood cells, they swell, rupture, and hemoglobin passes into the plasma. Such blood is called "lacquer", and the process is called hemolysis.

In severe conditions, doctors watch for the need to add saline solutions or water to prevent disruption of tissue breathing.

The properties of erythrocytes provide the body with resistance to environmental conditions, compatibility with external influences. The analysis for erythrocytes is part of the blood formula and is necessarily checked for any violations of the patient's well-being.

And then they carry it (oxygen) through the body of the animal.

Encyclopedic YouTube

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  Red blood cells are highly specialized cells whose function is to transport oxygen from the lungs to body tissues and transport carbon dioxide (CO 2) in the opposite direction. In vertebrates, except for mammals, erythrocytes have a nucleus, in mammalian erythrocytes there is no nucleus.

  Mammalian erythrocytes are the most specialized, devoid of a nucleus and organelles in the mature state and having the shape of a biconcave disk, which causes a high area-to-volume ratio, which facilitates gas exchange. Features of the cytoskeleton and cell membrane allow erythrocytes to undergo significant deformations and restore their shape (human erythrocytes with a diameter of 8 microns pass through capillaries with a diameter of 2-3 microns).

  Oxygen transport is provided by hemoglobin (Hb), which accounts for ≈98% of the mass of erythrocyte cytoplasmic proteins (in the absence of other structural components). Hemoglobin is a tetramer in which each protein chain carries a heme - a complex of protoporphyrin IX with a 2-valent iron ion, oxygen is reversibly coordinated with the Fe 2+ ion of hemoglobin, forming oxyhemoglobin HbO 2:

  Hb + O 2 HbO 2

  A feature of oxygen binding by hemoglobin is its allosteric regulation - the stability of oxyhemoglobin decreases in the presence of 2,3-diphosphoglyceric acid, an intermediate product of glycolysis and, to a lesser extent, carbon dioxide, which contributes to the release of oxygen in tissues that need it.

  The transport of carbon dioxide by erythrocytes occurs with the participation of carbonic anhydrase 1 contained in their cytoplasm. This enzyme catalyzes the reversible formation of bicarbonate from water and carbon dioxide diffusing into red blood cells:

  H 2 O + CO 2 ⇌ (\displaystyle \rightleftharpoons ) H + + HCO 3 -

  As a result, hydrogen ions accumulate in the cytoplasm, but the decrease is insignificant due to the high buffer capacity of hemoglobin. Due to the accumulation of bicarbonate ions in the cytoplasm, a concentration gradient arises, however, bicarbonate ions can leave the cell only if the equilibrium distribution of charges between the internal and external environment, separated by the cytoplasmic membrane, is maintained, that is, the exit of the bicarbonate ion from the erythrocyte must be accompanied by either the exit of the cation or the entry of the anion. The erythrocyte membrane is practically impermeable to cations, but contains chloride ion channels, as a result, the release of bicarbonate from the erythrocyte is accompanied by the entry of a chloride anion into it (chloride shift).

  RBC formation

  The erythrocyte colony-forming unit (CFU-E) gives rise to erythroblast, which, through the formation of pronormoblasts, already gives rise to morphologically distinguishable normoblast descendant cells (successively passing stages):

  • Erythroblast. Its distinguishing features are as follows: a diameter of 20-25 microns, a large (more than 2/3 of the entire cell) nucleus with 1-4 clearly defined nucleoli, a bright basophilic cytoplasm with a purple tint. Around the nucleus there is an enlightenment of the cytoplasm (the so-called "perinuclear enlightenment"), and protrusions of the cytoplasm (the so-called "ears") can form on the periphery. The last 2 signs, although they are characteristic of etitroblasts, are not observed in all of them.
  • Pronormocyte. Distinctive features: diameter 10-20 microns, the nucleus is deprived of nucleoli, chromatin coarsens. The cytoplasm begins to lighten, perinuclear enlightenment increases in size.
  • Basophilic normoblast. Distinctive features: diameter 10-18 microns, devoid of nucleolus nucleus. Chromatin begins to segment, which leads to uneven perception of dyes, the formation of oxy- and basochromatin zones (the so-called "wheel-shaped nucleus").
  • Polychromatophilic normoblast. Distinguishing features: diameter 9-12 microns, pycnotic (destructive) changes begin in the nucleus, however, wheel-like shape is preserved. The cytoplasm becomes oxyphilic due to the high concentration of hemoglobin.
  • Oxyphilic normoblast. Distinctive features: diameter 7-10 microns, the nucleus is subject to pycnosis and is displaced to the cell periphery. The cytoplasm is clearly pink; fragments of chromatin (Joli bodies) are found in it near the nucleus.
  • Reticulocyte. Distinctive features: diameter 9-11 microns, with supravital coloring it has a yellow-green cytoplasm and a blue-violet reticulum. When stained according to Romanovsky-Giemsa, no distinguishing features are revealed in comparison with a mature erythrocyte. In the study of the usefulness, speed and adequacy of erythropoiesis, a special analysis of the number of reticulocytes is carried out.
  • Normocyte. Mature erythrocyte, with a diameter of 7-8 microns, without a nucleus (in the center - enlightenment), the cytoplasm is pink-red.

  Hemoglobin begins to accumulate already at the CFU-E stage, however, its concentration becomes high enough to change the color of the cell only at the level of a polychromatophilic normocyte. Extinction (and subsequently destruction) of the nucleus occurs in the same way - with CFU, but it is forced out only in the later stages. An important role in this process in humans is played by hemoglobin (its main type is Hb-A), which in high concentration is toxic to the cell itself.

  Structure and composition

  In most groups of vertebrates, erythrocytes have a nucleus and other organelles.

  In mammals, mature erythrocytes lack nuclei, internal membranes, and most organelles. Nuclei are ejected from progenitor cells during erythropoiesis. Typically, mammalian erythrocytes are shaped like a biconcave disc and contain mainly the respiratory pigment hemoglobin. In some animals (for example, camels), red blood cells are oval in shape.

  The content of the erythrocyte is represented mainly by the respiratory pigment hemoglobin, which determines the red color of the blood. However, in the early stages, the amount of hemoglobin in them is small, and at the stage of erythroblasts, the color of the cell is blue; later the cell becomes gray and, only when fully matured, acquires a red color.

  An important role in the erythrocyte is played by the cell (plasma) membrane, which allows gases (oxygen, carbon dioxide), ions ( , ) and water to pass through. The membrane is permeated by transmembrane proteins - glycophorins, which, due to the large number of residues of N-acetylneuraminic (sialic) acid, are responsible for approximately 60% of the negative charge on the surface of erythrocytes.

  On the surface of the lipoprotein membrane there are specific antigens of a glycoprotein nature - agglutinogens - factors of blood group systems (at the moment more than 15 blood group systems have been studied: AB0, Rh factor, antigen Duffy (English) Russian, antigen Kell , antigen Kidd (English) Russian), causing erythrocyte agglutination under the action of specific agglutinins.

  The efficiency of hemoglobin functioning depends on the size of the contact surface of the erythrocyte with the medium. The total surface of all red blood cells in the body is the larger, the smaller their size. In lower vertebrates, erythrocytes are large (for example, in a caudate amphibian amphium - 70 microns in diameter), erythrocytes of higher vertebrates are smaller (for example, in a goat - 4 microns in diameter). In humans, the diameter of an erythrocyte is 6.2-8.2 microns, thickness - 2 microns, volume - 76-110 microns³.

  • for men - 3.9-5.5⋅10 12 per liter (3.9-5.5 million in 1 mm³),
  • in women - 3.9-4.7⋅10 12 per liter (3.9-4.7 million in 1 mm³),
  • in newborns - up to 6.0⋅10 12 per liter (up to 6 million in 1 mm³),
  • in the elderly - 4.0⋅10 12 per liter (less than 4 million in 1 mm³).

  Blood transfusion

  The average lifespan of a human erythrocyte is 125 days (about 2.5 million erythrocytes are formed every second and the same number is destroyed), in dogs - 107 days, in domestic rabbits and cats - 68.

  Pathology

  With various diseases of the blood, it is possible to change the color of erythrocytes, their size, quantity, and shape; they may take, for example, crescent, oval, spherical or target-shaped.

  The change in the shape of red blood cells is called poikilocytosis. Spherocytosis (spherical shape of red blood cells) is observed in some forms of hereditary

  erythroblast

  The parent cell of the erythroid series is erythroblast. It originates from an erythropoietin-responsive cell that develops from a myelopoiesis progenitor cell.

  Erythroblast reaches a diameter of 20-25 microns. Its core has an almost geometrically round shape, painted in red-violet color. Compared to undifferentiated blasts, a coarser structure and a brighter coloration of the nucleus can be noted, although the chromatin filaments are rather thin, their interweaving is uniform, delicately reticulated. The nucleus contains two to four nucleoli or more. The cytoplasm of a cell with a purple tint. Enlightenment is observed around the nucleus (perinuclear zone), sometimes with a pink tint. These morphological and tinctorial features make it easy to recognize the erctroblast.

  Pronormocyte

  Pronormocyte (pronormoblast) like erythroblast, it is characterized by a clearly defined round nucleus and pronounced basophilia of the cytoplasm. It is possible to distinguish a pronormocyte from an erythroblast by the coarser structure of the nucleus and the absence of nucleoli in it.

  Normocyte

  Normocyte (normoblast) in size it approaches mature non-nuclear erythrocytes (8-12 microns) with deviations in one direction or another (micro- and macroforms).

  Depending on the degree of hemoglobin saturation distinguish between basophilic, polychromatophilic and oxyphilic (orthochromic) normocytes. The accumulation of hemoglobin in the cytoplasm of normocytes occurs with the direct participation of the nucleus. This is also evidenced by its appearance at first around the nucleus, in the perinuclear zone. Gradually, the accumulation of hemoglobin in the cytoplasm is accompanied by polychromasia - the cytoplasm becomes polychromatophilic, that is, it perceives both acidic and basic dyes. When the cell is saturated with hemoglobin, the cytoplasm of the normocyte in stained preparations becomes pink.

  Simultaneously with the accumulation of hemoglobin in the cytoplasm, the nucleus undergoes regular changes, in which the processes of condensation of nuclear chromatin occur. As a result, the nucleoli disappear, the chromatin network becomes coarser, and the nucleus acquires a characteristic radial (wheel-shaped) structure, chromatin and parachromatin are clearly distinguishable in it. These changes are characteristic of a polychromatophilic normocyte.

  Polychromatophilic normocyte- the last cell of the red row, which is still capable of division. Subsequently, in the oxyphilic normocyte, the chromatin of the nucleus thickens, becomes coarse-pycnotic, the cell loses its nucleus and turns into an erythrocyte.

  Under normal conditions, mature red blood cells enter the bloodstream from the bone marrow. In conditions of pathology associated with a deficiency of cyanocobalamin - vitamin B 12 (its coenzyme methylcobalamin) or folic acid, megaloblastic forms of erythrokaryocytes appear in the bone marrow.

  Promegaloblast

  Promegaloblast- the youngest form of the megaloblastic series. It is not always possible to establish morphological differences between promegaloblast and proerythrokaryocyte. Usually, the promegaloblast is larger in diameter (25-35 µm), the structure of its nucleus is distinguished by a clear pattern of the chromatin network with a border between chromatin and parachromatin. The cytoplasm is usually wider than that of the pronormocyte, and the nucleus is often located eccentrically. Sometimes attention is drawn to the uneven (filamentous) intense staining of the basophilic cytoplasm.

  Megaloblast

  Along with large megaloblasts (giant blasts), small cells can be observed, corresponding in size to normocytes. From the latter, megaloblasts differ in the delicate structure of the nucleus. In a normocyte, the nucleus is coarsely looped, with radian striation; in a megaloblast, it retains a delicate reticulation, fine granularity of chromatin clumps, is located in the center or eccentrically, and has no nucleoli.

  Early saturation of the cytoplasm with hemoglobin is the second important feature that distinguishes a megaloblast from a normocyte. Like normocytes, according to the content of hemoglobin in the cytoplasm, megaloblasts are divided into basophilic, polychromatophilic and oxyphilic.

  Polychromatophilic megaloblasts characterized by metachromatic color of the cytoplasm, which can acquire grayish-green hues.

  Since the hemoglobinization of the cytoplasm is ahead of the differentiation of the nucleus, the cell remains nucleated for a long time and cannot turn into a megalocyte. Compaction of the nucleus occurs with a delay (after several mitoses). At the same time, the size of the nucleus decreases (in parallel with the decrease in cell size to 12–15 µm), but its chromatin never acquires the wheel-shaped structure characteristic of the normocyte nucleus. In the process of involution, the nucleus of the megaloblast takes on all sorts of forms. This leads to the formation of megaloblasts with the most diverse, bizarre forms of nuclei and their remnants, Jolly bodies, Cabot rings, Weidenreich nuclear dust particles.

  Megalocyte

  Freed from the nucleus, the megaloblast turns into a megalocyte, which differs from a mature erythrocyte in size (10-14 microns or more) and hemoglobin saturation. It is predominantly oval in shape, without enlightenment in the center.

  red blood cells

  Erythrocytes make up the bulk of the cellular elements of the blood. Under normal conditions, the blood contains from 4.5 to 5 T (10 12) in 1 liter of erythrocytes. The idea of ​​the total volume of erythrocytes gives the hematocrit number - the ratio of the volume of blood cells to the volume of plasma.

  The erythrocyte has a plasmalemma and a stroma. The plasmalemma is selectively permeable to a number of substances, mainly gases, in addition, it contains various antigens. The stroma also contains blood antigens, as a result of which it determines to a certain extent the grouping of the blood. In addition, the stroma of erythrocytes contains the respiratory pigment hemoglobin, which provides oxygen fixation and its delivery to tissues. This is due to the ability of hemoglobin to form an unstable compound oxyhemoglobin with oxygen, from which oxygen is easily split off, diffusing into the tissue, and oxyhemoglobin is again converted into reduced hemoglobin. Erythrocytes are actively involved in the regulation of the acid-base state of the body, the adsorption of toxins and antibodies, as well as in a number of enzymatic processes.

  Fresh, non-fixed erythrocytes have the appearance of biconcave discs, round or oval, stained pink according to Romanovsky. The biconcave surface of erythrocytes contributes to the fact that a larger surface is involved in oxygen exchange than with spherical cells. Due to the concavity of the middle part of the erythrocyte under the microscope, its peripheral section appears darker than the central one.

  Reticulocytes

  With supravital staining, granuloretnculofilamentous substance (reticulum) is detected in newly formed erythrocytes that have entered the bloodstream from the bone marrow. Red blood cells with this substance are called reticulocytes..

  Normal blood contains 0.1 to 1% reticulocytes. It is now believed that all young RBCs go through the reticulocyte stage. and the transformation of a reticulocyte into a mature erythrocyte occurs in a short period of time (29 h Finch). During this time, they finally lose their reticulum and turn into red blood cells.

  Meaning peripheral reticulocytosis as an indicator of the functional state of the bone marrow due to the fact that the increased intake of young erythrocytes into the peripheral blood (increased physiological regeneration of erythrocytes) is combined with increased hematopoietic activity of the bone marrow. Thus, the effectiveness of erythrocytopoiesis can be judged by the number of reticulocytes.

  In some cases, an increased content of reticulocytes is of diagnostic value, indicating the source of bone marrow irritation. For example, a reticulocyte reaction in jaundice indicates the hemolytic nature of the disease; pronounced reticulocytosis helps to detect hidden bleeding.

  By the number of reticulocytes, one can also judge the effectiveness of treatment (for bleeding, hemolytic anemia, etc.). This is the practical significance of the study of reticulocytes.

  A sign of normal bone marrow regeneration can also be the detection in peripheral blood polychromatophilic erythrocytes. They are immature bone marrow reticulocytes, which are richer in RNA compared to peripheral blood reticulocytes. With the help of radioactive iron, it has been proved that some of the reticulocytes are formed from polychromatophilic normocytes without cell division. Such reticulocytes, formed under conditions of impaired erythrocytopoiesis, are larger in size and have a shortened lifespan compared to normal reticulocytes.

  Bone marrow reticulocytes linger in the stroma of the bone marrow for 2-4 days, and then enter the peripheral blood. In cases of hypoxia (blood loss, hemolysis), bone marrow reticulocytes appear in the peripheral blood at an earlier date. In severe anemia, bone marrow reticulocytes can also form from basophilic normocytes. In peripheral blood, they look like basophilic erythrocytes.

  Polychromatophilia of erythrocytes(bone marrow reticulocytes) is due to the mixing of two highly dispersed colloidal phases, one of which (acid reaction) is a basophilic substance, and the other (weakly alkaline reaction) is hemoglobin. Due to the mixing of both colloidal phases, an immature erythrocyte, when stained according to Romanovsky, perceives both acidic and alkaline dyes, acquiring a grayish-pinkish color (stained polychromatophilically).

  The basophilic substance of polychromatophiles with supravital staining with a 1% solution of brilliant-cresyl blue (in a humid chamber) is detected in the form of a more pronounced reticulum.

  To determine the degree of erythrocyte regeneration, it was proposed to use a thick drop stained according to Romanovsky without fixation. At the same time, mature erythrocytes are leached and are not detected, and reticulocytes remain in the form of a basophilic (bluish-violet) colored mesh - polychromasia. An increase to three and four pluses indicates an increased regeneration of erythroid cells.

  Unlike normocytes, which are characterized by intensive synthesis of DNA, RNA, and lipids, only lipid synthesis continues in reticulocytes and RNA is present. It has also been established that hemoglobin synthesis continues in reticulocytes.

  The average normocyte diameter is about 7.2 μm, volume - 88 fl (μm 3), thickness - 2 μm, sphericity index - 3.6.