Erythrocytes are red blood cells. The number of erythrocytes in 1 mm 3 of blood in men is 4,500,000-5,500,000, in women 4,000,000-5,000,000. The main function of erythrocytes is participation in. Red blood cells carry out the absorption of oxygen in the lungs, its transport and return to tissues and organs, as well as the transport of carbon dioxide to the lungs. Erythrocytes are also involved in the regulation of acid-base balance and water-salt metabolism, in a number of enzymatic and metabolic processes. Erythrocytes - a non-nuclear cell, consisting of a semi-permeable protein-lipoid membrane and a spongy substance, the cells of which contain hemoglobin (see). The shape of erythrocytes is a biconcave disk. Normally, the diameter of erythrocytes ranges from 4.75 to 9.5 microns. Determining the size of red blood cells - see. A decrease in the average diameter of erythrocytes - microcytosis - is observed in some forms of iron deficiency and hemolytic anemia, an increase in the average diameter of erythrocytes - macrocytosis - with a deficiency and some liver diseases. Erythrocytes with a diameter of more than 10 microns, oval and hyperchromic - megalocytes - appear when pernicious anemia. The presence of red blood cells of various sizes - anisocytosis - accompanies most anemias; at severe anemia it is combined with poikilocytosis - a change in the shape of red blood cells. For some hereditary forms hemolytic anemias are characterized by erythrocytes - oval, sickle-shaped, target-shaped.
The color of erythrocytes under a microscope when stained according to Romanovsky - Giemsa - pink. The color intensity depends on the hemoglobin content (see Hyperchromasia, hypochromasia). Immature erythrocytes (pronormoblasts) contain a basophilic substance that stains blue. As hemoglobin accumulates, the blue color is gradually replaced by pink, the erythrocyte becomes polychromatophilic (lilac), which indicates its youth (normoblasts). With supravital staining with alkaline dyes, the basophilic substance of freshly isolated bone marrow erythrocytes is revealed in the form of grains and filaments. These red blood cells are called reticulocytes. The number of reticulocytes characterizes the ability of the bone marrow to red blood cells, normally they are 0.5-1% of all red blood cells. Reticulocyte granularity should not be confused with the basophilic granularity found in fixed and stained smears in blood disorders and lead poisoning. In severe anemia and leukemia, nucleated erythrocytes may appear in the blood. The bodies of Jolly and the rings of Cabot represent the remnants of the nucleus with its improper maturation. See also Blood.
Erythrocytes (from Greek erythros - red and kytos - cell) - red blood cells.
The number of red blood cells healthy men 4,500,000-5,500,000 in 1 mm 3, in women - 4,000,000-5,000,000 in 1 mm 3. Human erythrocytes have the shape of a biconcave disc with a diameter of 4.75-9.5 microns (average 7.2-7.5 microns) and a volume of 88 microns 3 . Erythrocytes do not have a nucleus, they have a membrane and stroma containing hemoglobin, vitamins, salts, enzymes. Electron microscopy showed that the stroma normal erythrocytes more often homogeneous, their shell is a semi-permeable membrane of lipoid-protein structure.
Rice. 1. Megalocytes (1), poikilocytes (2).
Rice. 2. Ovalocytes.
Rice. 3. Microcytes (1), macrocytes (2).
Rice. 4. Reticulocytes.
Rice. 5. Howell's bodies - Jolly (1), Cabot's ring (2).
The main function of erythrocytes is the absorption of oxygen by hemoglobin (see) in the lungs, its transportation and return to tissues and organs, as well as the perception of carbon dioxide, which erythrocytes carry to the lungs. The functions of erythrocytes are also the regulation of acid-base balance in the body (buffer system), the support of isotonicity of blood and tissues, the adsorption of amino acids and their transport to tissues. The lifespan of erythrocytes is on average 125 days; with blood diseases, it is significantly shortened.
With various anemias, changes in the shape of erythrocytes are observed: erythrocytes appear in the form of mulberries, pears (poikilocytes; Fig. 1, 2), crescents, balls, sickle, oval (Fig. 2); sizes (anisocytosis): erythrocytes in the form of macro- and microcytes (Fig. 3), schizocytes, gigantocytes and megalocytes (Fig. 1, 1); staining: erythrocytes in the form of hypochromia and hyperchromia (in the first case, the color indicator will be less than one due to iron deficiency, and in the second - more than one due to an increase in the volume of red blood cells). About 5% of erythrocytes, when stained according to Giemsa - Romanovsky, are not pink-red, but purple, since they are simultaneously stained with both acidic dye (eosin) and basic (methylene blue). These are polychromatophiles, which are an indicator of blood regeneration. More precisely, the processes of regeneration are indicated by reticulocytes (erythrocytes with a granular-filamentous substance - a mesh containing RNA), which normally make up 0.5-1% of all erythrocytes (Fig. 4). Indicators of pathological regeneration of erythropoiesis are basophilic puncture in erythrocytes, Howell-Jolly bodies and Cabot rings (remnants of the nuclear substance of normoblasts; Fig. 5).
In some anemias, more often hemolytic, the erythrocyte protein acquires antigenic properties with the formation of antibodies (autoantibodies). Thus, anti-erythrocyte autoantibodies arise - hemolysins, agglutinins, opsonins, the presence of which causes the destruction of erythrocytes (see Hemolysis). See also Immunohematology, Blood.
Human blood is a liquid substance consisting of plasma and suspended matter in it. shaped elements, or blood cells, which make up approximately 40-45% of the total volume. They are small and can only be seen under a microscope.
There are several types of blood cells that perform specific functions. Some of them function only inside the circulatory system, others go beyond it. What they all have in common is that they are all formed in the bone marrow from stem cells, the process of their formation is continuous, and their life span is limited.
All blood cells are divided into red and white. The first are erythrocytes, which make up most of all cells, the second are leukocytes.
Platelets are also considered to be blood cells. These small platelets are not actually complete cells. They are small fragments separated from large cells - megakaryocytes.
Erythrocytes are called red blood cells. This is the largest group of cells. They carry oxygen from the respiratory organs to the tissues and take part in the transportation carbon dioxide from tissues to lungs.
The place of formation of red blood cells is the red bone marrow. They live 120 days and are destroyed in the spleen and liver.
They are formed from precursor cells - erythroblasts, which undergo different stages development and are divided several times. Thus, up to 64 red blood cells are formed from an erythroblast.
Erythrocytes are devoid of a nucleus and in shape resemble a disc concave on both sides, the average diameter of which is about 7-7.5 microns, and the thickness along the edges is 2.5 microns. This shape helps to increase the plasticity required for passage through small vessels and the surface area for diffusion of gases. Old erythrocytes lose their plasticity, which is why they linger in small vessels spleen and there are destroyed.
Most of the erythrocytes (up to 80%) have a biconcave spherical shape. The remaining 20% may have a different one: oval, cup-shaped, simple spherical, sickle-shaped, etc. Violation of the shape is associated with various diseases(anemia, vitamin B12 deficiency, folic acid, iron, etc.).
Most of the cytoplasm of the erythrocyte is occupied by hemoglobin, consisting of protein and heme iron, which gives the blood a red color. The non-protein part consists of four heme molecules with an Fe atom in each. It is thanks to hemoglobin that the erythrocyte is able to carry oxygen and remove carbon dioxide. In the lungs, an iron atom binds to an oxygen molecule, hemoglobin is converted to oxyhemoglobin, which gives the blood a scarlet color. In tissues, hemoglobin gives off oxygen and attaches carbon dioxide, turning into carbohemoglobin, as a result, the blood becomes dark. In the lungs, carbon dioxide is separated from hemoglobin and excreted by the lungs to the outside, and the incoming oxygen again binds to iron.
In addition to hemoglobin, the cytoplasm of the erythrocyte contains various enzymes (phosphatase, cholinesterases, carbonic anhydrase, etc.).
The erythrocyte membrane has a fairly simple structure compared to the membranes of other cells. It is an elastic thin mesh, which ensures rapid gas exchange.
Antigens are found on the surface of red blood cells different types which determine the Rh factor and blood type. The Rh factor can be positive or negative depending on the presence or absence of the Rh antigen. The blood type depends on which antigens are on the membrane: 0, A, B (the first group is 00, the second is 0A, the third is 0B, the fourth is AB).
In the blood of a healthy person, there may be small amounts of immature red blood cells called reticulocytes. Their number increases with significant blood loss, when replacement of red cells is required and the bone marrow does not have time to produce them, therefore it releases immature ones, which, nevertheless, are able to perform the functions of red blood cells for transporting oxygen.
Leukocytes are white blood cells whose main task is to protect the body from internal and external enemies.
They are usually divided into granulocytes and agranulocytes. The first group is granular cells: neutrophils, basophils, eosinophils. The second group does not have granules in the cytoplasm, it includes lymphocytes and monocytes.
This is the most numerous group of leukocytes - up to 70% of total number white cells. Neutrophils got their name due to the fact that their granules are stained with dyes with a neutral reaction. Its granularity is fine, the granules have a purple-brownish tint.
The main task of neutrophils is phagocytosis, which is to capture pathogenic microbes and products of tissue breakdown and their destruction inside the cell with the help of lysosomal enzymes located in the granules. These granulocytes fight mainly bacteria and fungi and, to a lesser extent, viruses. Pus consists of neutrophils and their residues. Lysosomal enzymes are released during the breakdown of neutrophils and soften nearby tissues, thus forming a purulent focus.
A neutrophil is a round-shaped nuclear cell, reaching a diameter of 10 microns. The core may be rod-shaped or consist of several segments (from three to five) connected by strands. An increase in the number of segments (up to 8-12 or more) indicates pathology. Thus, neutrophils can be stab or segmented. The first are young cells, the second are mature. Cells with a segmented nucleus make up to 65% of all leukocytes, stab cells in the blood of a healthy person - no more than 5%.
In the cytoplasm there are about 250 varieties of granules containing substances due to which the neutrophil performs its functions. These are protein molecules that affect metabolic processes (enzymes), regulatory molecules that control the work of neutrophils, substances that destroy bacteria and other harmful agents.
These granulocytes are formed in the bone marrow from neutrophilic myeloblasts. A mature cell stays in the brain for 5 days, then enters the bloodstream and lives here for up to 10 hours. From the vascular bed, neutrophils enter the tissues, where they stay for two or three days, then they enter the liver and spleen, where they are destroyed.
There are very few of these cells in the blood - no more than 1% of the total number of leukocytes. They have a rounded shape and a segmented or rod-shaped nucleus. Their diameter reaches 7-11 microns. Inside the cytoplasm are dark purple granules of various sizes. The name was given due to the fact that their granules are stained with dyes with an alkaline, or basic (basic) reaction. Basophil granules contain enzymes and other substances involved in the development of inflammation.
Their main function is the release of histamine and heparin and participation in the formation of inflammatory and allergic reactions, including immediate type (anaphylactic shock). In addition, they can reduce blood clotting.
Formed in the bone marrow from basophilic myeloblasts. After maturation, they enter the blood, where they stay for about two days, then go into the tissues. What happens next is still unknown.
These granulocytes make up approximately 2-5% of the total white cells. Their granules are stained with an acidic dye - eosin.
They have a rounded shape and a weakly colored core, consisting of segments of the same size (usually two, less often three). In diameter, eosinophils reach 10-11 microns. Their cytoplasm stains pale blue and is almost invisible among a large number large round granules of yellow-red color.
These cells are formed in the bone marrow, their precursors are eosinophilic myeloblasts. Their granules contain enzymes, proteins and phospholipids. A mature eosinophil lives in the bone marrow for several days, after entering the blood it stays in it for up to 8 hours, then moves to tissues that have contact with external environment(mucous membranes).
These are round cells with a large nucleus that occupies most of the cytoplasm. Their diameter is 7 to 10 microns. The kernel is round, oval or bean-shaped, has a rough structure. It consists of lumps of oxychromatin and basiromatin, resembling lumps. The nucleus may be dark purple or light purple, sometimes there are light blotches in the form of nucleoli. The cytoplasm is stained light blue, around the nucleus it is lighter. In some lymphocytes, the cytoplasm has an azurophilic granularity that turns red when stained.
Two types of mature lymphocytes circulate in the blood:
- Narrow plasma. They have a rough, dark purple nucleus and a narrow blue-rimmed cytoplasm.
- Wide plasma. In this case, the kernel has a paler color and a bean-shaped shape. The rim of the cytoplasm is quite wide, gray-blue in color, with rare ausurophilic granules.
Of the atypical lymphocytes in the blood, one can detect:
- Small cells with barely visible cytoplasm and pycnotic nucleus.
- Cells with vacuoles in the cytoplasm or nucleus.
- Cells with lobulated, kidney-shaped, notched nuclei.
- Naked kernels.
Lymphocytes are formed in the bone marrow from lymphoblasts and in the process of maturation they go through several stages of division. Its full maturation occurs in the thymus, lymph nodes and spleen. Lymphocytes are immune cells that provide immune responses. There are T-lymphocytes (80% of the total) and B-lymphocytes (20%). The first passed maturation in the thymus, the second - in the spleen and lymph nodes. B-lymphocytes are larger in size than T-lymphocytes. The life span of these leukocytes is up to 90 days. Blood for them is a transport medium through which they enter the tissues where their help is required.
The actions of T-lymphocytes and B-lymphocytes are different, although both are involved in the formation of immune responses.
The former are engaged in the destruction of harmful agents, usually viruses, by phagocytosis. The immune reactions in which they participate are non-specific resistance, since the actions of T-lymphocytes are the same for all harmful agents.
According to the actions performed, T-lymphocytes are divided into three types:
- T-helpers. Their main task is to help B-lymphocytes, but in some cases they can act as killers.
- T-killers. They destroy harmful agents: foreign, cancerous and mutated cells, infectious agents.
- T-suppressors. They inhibit or block too active reactions of B-lymphocytes.
B-lymphocytes act differently: against pathogens, they produce antibodies - immunoglobulins. This happens as follows: in response to the actions of harmful agents, they interact with monocytes and T-lymphocytes and turn into plasma cells that produce antibodies that recognize the corresponding antigens and bind them. For each type of microbes, these proteins are specific and can only destroy certain kind, therefore, the resistance that these lymphocytes form is specific, and it is directed mainly against bacteria.
These cells provide the body with resistance to certain harmful microorganisms what is called immunity. That is, having met with a harmful agent, B-lymphocytes create memory cells that form this resistance. The same thing - the formation of memory cells - is achieved by vaccinations against infectious diseases. In this case, a weak microbe is introduced so that the person can easily endure the disease, and as a result, memory cells are formed. They can remain for life or for a certain period, after which the vaccination is required to be repeated.
Monocytes are the largest of the white blood cells. Their number is from 2 to 9% of all white blood cells. Their diameter reaches 20 microns. The monocyte nucleus is large, occupies almost the entire cytoplasm, can be round, bean-shaped, have the shape of a mushroom, a butterfly. When stained, it becomes red-violet. The cytoplasm is smoky, bluish-smoky, rarely blue. It usually has an azurophilic fine grain. It may contain vacuoles (voids), pigment grains, phagocytosed cells.
Monocytes are produced in the bone marrow from monoblasts. After maturation, they immediately appear in the blood and stay there for up to 4 days. Some of these leukocytes die, some move to tissues, where they mature and turn into macrophages. These are the largest cells with a large round or oval nucleus, blue cytoplasm and a large number vacuoles, which makes them appear frothy. The life span of macrophages is several months. They can constantly be in one place (resident cells) or move (wandering).
Monocytes form regulatory molecules and enzymes. They are able to form an inflammatory reaction, but they can also slow it down. In addition, they are involved in the process of wound healing, helping to speed it up, contribute to the restoration of nerve fibers and bone tissue. Their main function is phagocytosis. Monocytes destroy harmful bacteria and prevent the reproduction of viruses. They are able to carry out commands, but cannot distinguish between specific antigens.
These blood cells are small non-nucleated plates and may be round or oval in shape. During activation, when they are at the damaged vessel wall, they form outgrowths, so they look like stars. Platelets contain microtubules, mitochondria, ribosomes, specific granules containing substances necessary for blood clotting. These cells are equipped with a three-layer membrane.
Platelets are produced in the bone marrow, but in a completely different way than other cells. Platelets are formed from the largest brain cells - megakaryocytes, which, in turn, were formed from megakaryoblasts. Megakaryocytes have a very large cytoplasm. After cell maturation, membranes appear in it, dividing it into fragments, which begin to separate, and thus platelets appear. They leave the bone marrow into the blood, stay in it for 8-10 days, then die in the spleen, lungs, and liver.
Platelets may have different sizes:
- the smallest are microforms, their diameter does not exceed 1.5 microns;
- normoforms reach 2-4 microns;
- macroforms - 5 µm;
- megaloforms - 6-10 microns.
Platelets perform very important function- they are involved in the formation of a blood clot, which closes the damage in the vessel, thereby preventing blood from flowing out. In addition, they maintain the integrity of the vessel wall, contribute to its fastest recovery after damage. When bleeding begins, platelets stick to the edge of the lesion until the hole is completely closed. Adhering plates begin to break down and release enzymes that act on blood plasma. As a result, insoluble fibrin strands are formed, tightly covering the injury site.
Conclusion
Blood cells have complex structure, and each type performs certain work: from the transport of gases and substances to the production of antibodies against foreign microorganisms. Their properties and functions are not fully understood to date. For normal life a person needs a certain amount of each type of cell. According to their quantitative and qualitative changes, physicians have the opportunity to suspect the development of pathologies. The composition of the blood is the first thing that the doctor studies when the patient is contacted.
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This part deals with the size, number and shape of erythrocytes, hemoglobin: its structure and properties, erythrocyte resistance, erythrocyte sedimentation reaction - ROE.
Erythrocytes.
Size, number and shape of red blood cells.
Erythrocytes - red blood cells - carry the respiratory function in the body. The size, number and shape of erythrocytes are well adapted to its implementation. human erythrocytes - small cells, whose diameter is 7.5 µm. Their number is large: in total, about 25x10 12 erythrocytes circulate in human blood. Usually determine the number of red blood cells in 1 mm 3 of blood. It is 5,000,000 for men and 4,500,000 for women. General surface erythrocytes - 3200 m 2, which is 1500 times the surface of the human body.
The erythrocyte has the shape of a biconcave disc. This form of an erythrocyte contributes to its better saturation with oxygen, since any point of it is no more than 0.85 microns from the surface. If the erythrocyte were spherical, its center would be 2.5 µm away from the surface.
The erythrocyte is covered with a protein-lipid membrane. The skeleton of an erythrocyte is called the stroma, which makes up 10% of its volume. A feature of erythrocytes is the absence of the endoplasmic reticulum, 71% of the erythrocyte is water. There is no nucleus in human erythrocytes. This peculiarity that has arisen in the process of evolution (in fish, amphibians, and erythrocytes have a nucleus) is also aimed at improving the respiratory function: in the absence of a nucleus, an erythrocyte can contain a greater amount of hemoglobin that carries oxygen. The absence of a nucleus is associated with the inability to synthesize protein and other substances in mature erythrocytes. In the blood (about 1%) there are precursors of mature erythrocytes - reticulocytes. They differ big size and the presence of a reticulate-filamentous substance, which includes ribonucleic acid, fats and some other compounds. In reticulocytes, the synthesis of hemoglobin, proteins and fats is possible.
Hemoglobin, its structure and properties.
Hemoglobin (Hb) - the respiratory pigment of human blood - consists of an active group, including four heme molecules, and a protein carrier - globin. Heme contains ferrous iron, which determines the ability of hemoglobin to carry oxygen. One gram of hemoglobin contains 3.2-3.3 mg of iron. Globin consists of alpha and beta polypeptide chains, each containing 141 amino acids. Hemoglobin molecules are very densely packed in the erythrocyte, due to which total hemoglobin in the blood is quite large: 700-800 g. 100 ml of blood in men contains about 16% hemoglobin, in women - about 14%. It has been established that not all hemoglobin molecules in human blood are identical. There are hemoglobin A 1, which accounts for up to 90% of the total hemoglobin in the blood, hemoglobin A 2 (2-3%) and A 3. Different types of hemoglobin differ in the sequence of amino acids in globin.
When non-hemoglobin is exposed to various reagents, globin is unhooked and various heme derivatives are formed. Beneath the weak mineral acids or alkalis, the heme of hemoglobin is converted to hematin. When exposed to heme concentrated acetic acid in the presence of NaCl, a crystalline substance called hemin is formed. Due to the fact that hemin crystals have a characteristic shape, their definition is very great importance in the practice of forensic medicine to detect blood stains on any subject.
An extremely important property of hemoglobin, which determines its importance in the body, is the ability to combine with oxygen. The combination of hemoglobin with oxygen is called oxyhemoglobin (HbO 2). One hemoglobin molecule can bind 4 oxygen molecules. Oxyhemoglobin is a fragile compound that easily dissociates into hemoglobin and oxygen. Due to the property of hemoglobin, it is easy to combine with oxygen and it is also easy to give it away, oxygen is supplied to tissues. In the capillaries of the lungs, oxyhemoglobin is formed, in the capillaries of tissues it dissociates with the formation of again hemoglobin and oxygen, which is consumed by cells. In the supply of cells with oxygen is the main importance of hemoglobin, and with it the erythrocytes.
The ability of hemoglobin to convert to oxyhemoglobin and vice versa is of great importance in maintaining a constant blood pH. The hemoglobin-oxyhemoglobin system is buffer system blood.
The combination of hemoglobin with carbon monoxide (carbon monoxide) is called carboxyhemoglobin. Unlike oxyhemoglobin, which readily dissociates into hemoglobin and oxygen, carboxyhemoglobin dissociates very weakly. Due to this, in the presence of air carbon monoxide most of hemoglobin binds to it, thus losing the ability to carry oxygen. This leads to disruption tissue respiration which can cause death.
When hemoglobin is exposed to nitrogen oxides and other oxidizing agents, methemoglobin is formed, which, like carboxyhemoglobin, cannot serve as an oxygen carrier. Hemoglobin can be distinguished from its carboxy- and methemoglobin derivatives by the difference in absorption spectra. The absorption spectrum of hemoglobin is characterized by one broad band. Oxyhemoglobin has two absorption bands in the spectrum, also located in the yellow-green part of the spectrum.
Methemoglobin gives 4 absorption bands: in the red part of the spectrum, on the border of red and orange, in yellow-green and blue-green. The spectrum of carboxyhemoglobin has the same absorption bands as the spectrum of oxyhemoglobin. The absorption spectra of hemoglobin and its compounds can be viewed in the upper right corner (illustration No. 2)
Erythrocyte resistance.
Erythrocytes retain their function only in isotonic solutions. V hypertonic solutions The waste from red blood cells enters the plasma, which leads to their wrinkling and loss of their function. In hypotonic solutions, water from the plasma rushes into the erythrocytes, which swell, burst, and hemoglobin is released into the plasma. The destruction of erythrocytes in hypotonic solutions is called hemolysis, and hemolyzed blood is called varnish for its characteristic color. The intensity of hemolysis depends on the resistance of erythrocytes. The resistance of erythrocytes is determined by the concentration of the NaCl solution at which hemolysis begins, characterizes the minimum resistance. The concentration of the solution at which all erythrocytes are destroyed determines the maximum resistance. At healthy people the minimum resistance is determined by the concentration table salt 0.30-0.32, maximum - 0.42-0.50%. The resistance of erythrocytes varies with different functional states organism.
Erythrocyte sedimentation reaction - ROE.
Blood is a stable suspension of formed elements. This property of blood is associated with the negative charge of erythrocytes, which interferes with the process of their gluing - aggregation. This process is very weakly expressed in moving blood. The coin-shaped accumulations of erythrocytes, which can be seen in freshly drawn blood, are a consequence of this process.
If the blood, mixed with a solution that prevents its coagulation, is placed in a graduated capillary, then the erythrocytes, undergoing aggregation, settle to the bottom of the capillary. Upper layer blood, losing erythrocytes, becomes transparent. The height of this unstained column of plasma determines the erythrocyte sedimentation reaction (ERS). The value of ROE in men is from 3 to 9 mm/h, in women - from 7 to 12 mm/h. In pregnant women, ROE can increase up to 50 mm / h.
The process of aggregation sharply increases with a change in the protein composition of the plasma. An increase in the amount of globulins in the blood inflammatory diseases accompanied by their adsorption by erythrocytes, a decrease in the electric charge of the latter and a change in the properties of their surface. This enhances the process of erythrocyte aggregation, which is accompanied by an increase in ROE.
red blood cells (erythrosytus) are the formed elements of the blood.
RBC function
The main functions of erythrocytes are the regulation of CBS in the blood, the transport of O 2 and CO 2 throughout the body. These functions are realized with the participation of hemoglobin. In addition, erythrocytes adsorb and transport amino acids, antibodies, toxins and a number of medicinal substances on their cell membrane.
Structure and chemical composition erythrocytes
Erythrocytes in humans and mammals in the blood stream usually (80%) have the shape of biconcave discs and are called discocytes . This form of erythrocytes creates the largest surface area in relation to volume, which ensures maximum gas exchange, and also provides greater plasticity when erythrocytes pass through small capillaries.
The diameter of erythrocytes in humans ranges from 7.1 to 7.9 microns, the thickness of erythrocytes in the marginal zone is 1.9 - 2.5 microns, in the center - 1 micron. V normal blood the specified sizes have 75% of all erythrocytes - normocytes ; large sizes (over 8.0 microns) - 12.5% - macrocytes . The rest of the erythrocytes may have a diameter of 6 microns or less - microcytes .
The surface area of a single human erythrocyte is approximately 125 µm 2 , and the volume (MCV) is 75-96 µm 3 .
Human and mammalian erythrocytes are nuclear-free cells that have lost the nucleus and most organelles during phylogenesis and ontogenesis, they have only the cytoplasm and plasmolemma (cell membrane).
Plasma membrane of erythrocytes
The plasmalemma of erythrocytes has a thickness of about 20 nm. It consists of approximately equal amounts of lipids and proteins, as well as a small amount of carbohydrates.
Lipids
The bilayer of the plasmalemma is formed by glycerophospholipids, sphingophospholipids, glycolipids, and cholesterol. The outer layer contains glycolipids (about 5% of the total lipids) and a lot of choline (phosphatidylcholine, sphingomyelin), the inner one contains a lot of phosphatidylserine and phosphatidylethanolamine.
Squirrels
In the plasmolemma of the erythrocyte, 15 major proteins with a molecular weight of 15-250 kDa have been identified.
Proteins spectrin, glycophorin, band 3 protein, band 4.1 protein, actin, ankyrin form a cytoskeleton on the cytoplasmic side of the plasmalemma, which gives the erythrocyte a biconcave shape and high mechanical strength. More than 60% of all membrane proteins are on the spectrin ,glycophorin (found only in the erythrocyte membrane) and protein strip 3 .
Spectrin - the main protein of the erythrocyte cytoskeleton (makes up 25% of the mass of all membrane and membrane proteins), has the form of a 100 nm fibril, consisting of two antiparallel twisted chains of α-spectrin (240 kDa) and β-spectrin (220 kDa). The spectrin molecules form a network that is fixed on the cytoplasmic side of the plasmalemma by ankyrin and band 3 protein or actin, band 4.1 protein and glycophorin.
Protein strip 3 - transmembrane glycoprotein (100 kDa), its polypeptide chain many times crosses the lipid bilayer. Band 3 protein is a cytoskeletal component and an anion channel that provides a transmembrane antiport for HCO 3 - and Cl - ions.
Glycophorin - transmembrane glycoprotein (30 kDa), which penetrates the plasma membrane in the form of a single helix. From the outer surface of the erythrocyte, 20 oligosaccharide chains are attached to it, which carry negative charges. Glycophorins form the cytoskeleton and, through oligosaccharides, perform receptor functions.
Na + ,K + -ATP-ase membrane enzyme, maintains the concentration gradient of Na + and K + on both sides of the membrane. With a decrease in the activity of Na + ,K + -ATPase, the concentration of Na + in the cell increases, which leads to an increase in osmotic pressure, an increase in the flow of water into the erythrocyte and to its death as a result of hemolysis.
Sa 2+ -ATP-ase - a membrane enzyme that removes calcium ions from erythrocytes and maintains a concentration gradient of this ion on both sides of the membrane.
Carbohydrates
Oligosaccharides (sialic acid and antigenic oligosaccharides) of glycolipids and glycoproteins located on the outer surface of the plasmalemma form glycocalyx . Glycophorin oligosaccharides determine the antigenic properties of erythrocytes. They are agglutinogens (A and B) and provide agglutination (gluing) of erythrocytes under the influence of the corresponding blood plasma proteins - - and -agglutinins, which are part of the -globulin fraction. Agglutinogens appear on the membrane at early stages erythrocyte development.
On the surface of red blood cells there is also an agglutinogen - the Rh factor (Rh factor). It is present in 86% of people, 14% absent. Transfusion of Rh-positive blood into an Rh-negative patient causes the formation of Rh antibodies and hemolysis of red blood cells.
RBC cytoplasm
The cytoplasm of erythrocytes contains about 60% water and 40% dry residue. 95% of the dry residue is hemoglobin, it forms numerous granules 4-5 nm in size. The remaining 5% of the dry residue falls on organic (glucose, intermediate products of its catabolism) and inorganic substances. Of the enzymes in the cytoplasm of erythrocytes, there are enzymes of glycolysis, PFS, antioxidant protection and the methemoglobin reductase system, carbonic anhydrase.
Blood is a viscous red liquid that flows through circulatory system: consists of a special substance - plasma, which carries throughout the body different kinds formed elements of blood and many other substances.
;Supply oxygen and nutrients the whole organism.
; Transfer metabolic products and toxic substances to the organs responsible for their neutralization.
transfer hormones produced endocrine glands, to the fabrics for which they are intended.
Take part in thermoregulation of the body.
; Interact with the immune system.
- blood plasma. It is a fluid that is 90% water, carrying all the elements present in the blood through cardiovascular system: in addition to transporting blood cells, spasma also supplies the organs with nutrients, minerals, vitamins, hormones and other products involved in biological processes, and carries away metabolic products. Some of these substances are themselves freely transported by the pasma, but many of them are insoluble and are transported only together with the proteins to which they are attached, and are separated only in the corresponding organ.
- blood cells. Looking at the composition of blood, you will see three types of blood cells: red blood cells, the same color as blood, the main elements that give it a red color; white blood cells responsible for many functions; and platelets, the smallest blood cells.
red blood cells, also called erythrocytes or red platelets, are fairly large blood cells. They are shaped like a biconcave disc and about 7.5 µm in diameter, they are not really cells as such, since they lack a nucleus; red blood cells live for about 120 days. red blood cells contain hemoglobin - a pigment consisting of iron, due to which the blood has a red color; it is hemoglobin that is responsible for the main function of the blood - the transfer of oxygen from the lungs to the tissues and the metabolic product - carbon dioxide - from the tissues to the lungs.
Red blood cells under a microscope.
If you line up everything red blood cells of an adult human, you get more than two trillion cells (4.5 million per mm3 times 5 liters of blood), they can be placed 5.3 times around the equator.
white blood cells, also called leukocytes, play an important role in immune system protecting the body from infections. There are several types of white blood cells; they all have a nucleus, including some multinucleated leukocytes, and are characterized by bizarre segmented nuclei that are visible under a microscope, so leukocytes are divided into two groups: polynuclear and mononuclear.
Polynuclear leukocytes also called granulocytes, since under a microscope you can see several granules in them, in which there are substances necessary to perform certain functions. There are three main types of granulocytes:
Let us dwell in more detail on each of the three types of granulocytes. You can consider granulocytes and cells, the descriptions of which will follow later in the article, in Scheme 1 below.
Scheme 1. Blood cells: white and red blood cells, platelets.
Neutrophilic granulocytes (Gy/n)- These are mobile spherical cells with a diameter of 10-12 microns. The nucleus is segmented, the segments are connected by thin heterochromatic bridges. In women, a small, elongated process called drumstick(Barr body); it corresponds to the inactive long arm of one of the two X chromosomes. On the concave surface of the nucleus is a large Golgi complex; other organelles are less developed. Characteristic of this group of leukocytes is the presence of cell granules. Azurophilic, or primary, granules (AG) are considered as primary lysosomes from the moment when they already contain acid phosphatase, aryleulfatase, B-galactosidase, B-glucuronidase, 5-nucleotidase d-aminooxidase, and peroxidase. Specific secondary, or neutrophilic, granules (NG) contain the bactericidal substances lysozyme and phagocytin, as well as the enzyme alkaline phosphatase. Neutrophil granulocytes are microphages, i.e. they absorb small particles such as bacteria, viruses, small parts of collapsing cells. These particles enter the cell body by capturing them by short cell processes, and then are destroyed in phagolysosomes, into which azurophilic and specific granules release their contents. The life cycle of neutrophilic granulocytes is about 8 days.
Eosinophilic granulocytes (Gy/e)- cells up to 12 µm in diameter. The nucleus is bipartite, the Golgi complex is located near the concave surface of the nucleus. Cellular organelles are well developed. In addition to azurophilic granules (AG), the cytoplasm includes eosinophilic granules (EG). They have an elliptical shape and consist of a fine-grained osmiophilic matrix and single or multiple dense lamellar crystalloids (Cr). Lysosomal enzymes: lactoferrin and myeloperoxidase are concentrated in the matrix, while a large basic protein, toxic to some helminths, is located in the crystalloids.
Basophilic granulocytes (Gy/b) have a diameter of about 10-12 microns. The nucleus is reniform or divided into two segments. Cellular organelles are poorly developed. The cytoplasm includes small rare peroxidase-positive lysosomes, which correspond to azurophilic granules (AG), and large basophilic granules (BG). The latter contain histamine, heparin and leukotrienes. Histamine is a vasodilating factor, heparin acts as an anticoagulant (a substance that inhibits the activity of the blood coagulation system and prevents the formation of blood clots), and leukotrienes cause bronchial constriction. Eosinophilic chemotactic factor is also present in the granules, it stimulates the accumulation of eosinophilic granules at the sites of allergic reactions. Under the influence of substances that cause the release of histamine or IgE, in most allergic and inflammatory reactions degranulation of basophils may occur. In this regard, some authors believe that basophilic granulocytes are identical mast cells connective tissues, although the latter do not have peroxidase-positive granules.
There are two types mononuclear leukocytes:
- Monocytes, which phagocytose bacteria, detritus and other harmful elements;
- Lymphocytes that produce antibodies (B-lymphocytes) and attack aggressive substances (T-lymphocytes).
Monocytes (Mts)- the largest of all blood cells, about 17-20 microns in size. A large kidney-shaped eccentric nucleus with 2-3 nucleoli is located in the bulk cytoplasm of the cell. The Golgi complex is localized near the concave surface of the nucleus. Cellular organelles are poorly developed. Azurophilic granules (AG), i.e., lysosomes, are scattered within the cytoplasm.
Monocytes are highly mobile cells with high phagocytic activity. Since the absorption of such large particles, like whole cells or large parts of disintegrated cells, they are called macrophages. Monocytes regularly leave the bloodstream and enter the connective tissue. The surface of monocytes can be both smooth and containing, depending on the cellular activity, pseudopodia, filopodia, microvilli. Monocytes are involved in immunological reactions: they are involved in the processing of absorbed antigens, the activation of T-lymphocytes, the synthesis of interleukin and the production of interferon. The life span of monocytes is 60-90 days.
white blood cells, in addition to monocytes, exist as two functionally distinct classes called T- and B-lymphocytes, which cannot be distinguished morphologically, based on conventional histological examination methods. From a morphological point of view, young and mature lymphocytes are distinguished. Large young B- and T-lymphocytes (CL) 10–12 μm in size contain, in addition to the round nucleus, several cell organelles, among which there are small azurophilic granules (AG) located in a relatively wide cytoplasmic rim. Large lymphocytes are considered as a class of so-called natural killers (killer cells).
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