The erythrocyte, the structure and functions of which we consider in our article, is the most important component of blood. It is these cells that carry out gas exchange, providing respiration at the cellular and tissue level.
Erythrocyte: structure and function
The circulatory system of humans and mammals is characterized by the most perfect structure in comparison with other organisms. It consists of a four-chamber heart and a closed system of vessels through which blood continuously circulates. This tissue consists of a liquid component - plasma, and a number of cells: erythrocytes, leukocytes and platelets. Each cell plays its role. The structure of the human erythrocyte due to the functions performed. This concerns the size, shape, and number of these blood cells.
Features of the structure of red blood cells
Red blood cells have the shape of a biconcave disc. They are not able to move independently in the bloodstream, like leukocytes. To the tissues and internal organs, they come through the work of the heart. Red blood cells - prokaryotic cells. This means that they do not contain a decorated core. Otherwise they could not carry oxygen and carbon dioxide. This function is performed due to the presence of a special substance inside the cells - hemoglobin, which also determines the red color of human blood.
The structure and function of red blood cells is largely due to the peculiarities of this particular substance. Hemoglobin consists of two components. It is an iron component called heme, and globin protein. For the first time, the English biochemist Max Ferdinand Perut was able to decipher the spatial structure of this chemical compound. For this discovery in 1962, he was awarded the Nobel Prize. Hemoglobin is a member of the chromoprotein group. These include complex proteins consisting of a simple biopolymer and a prosthetic group. For hemoglobin, this group is heme. This group also includes chlorophyll plants, which ensures the photosynthesis process.
How does gas exchange occur?
In humans and other chordate animals, hemoglobin is located inside the erythrocytes, and in invertebrates it is dissolved directly in the blood plasma. In any case, the chemical composition of this complex protein allows the formation of unstable compounds with oxygen and carbon dioxide. Blood that is saturated with oxygen is called arterial. It is enriched with this gas in the lungs.
From the aorta, it goes to the arteries, and then to the capillaries. These smallest vessels fit every cell of the body. Here, erythrocytes donate oxygen and attach the main product of respiration - carbon dioxide. With the flow of blood, which is already venous, they enter the lungs again. In these organs, gas exchange occurs in the smallest vesicles - the alveoli. Here, hemoglobin removes carbon dioxide, which is removed from the body through exhalation, and the blood is again saturated with oxygen.
Such chemical reactions are due to the presence of bivalent iron in heme. As a result of the compound and decomposition, hydroxy- and carbhemoglobin are sequentially formed. But the complex protein of erythrocytes can also form persistent compounds. For example, in case of incomplete combustion of fuel, carbon monoxide is released, which forms carboxyhemoglobin with hemoglobin. This process leads to the death of red blood cells and poisoning of the body, which can be fatal.
What is anemia
Shortness of breath, palpable weakness, tinnitus, noticeable pallor of the skin and mucous membranes may indicate an insufficient amount of hemoglobin. The rate of its content varies depending on gender. For women, this figure is 120 - 140 g per 1000 ml of blood, and for men it reaches 180 g / l. The hemoglobin content in the blood of newborns is the largest. It exceeds this figure in adults, reaching 210 g / l.
Hemoglobin deficiency is a serious condition called anemia or anemia. It can be caused by a lack of vitamins and iron salts in food products, a predilection for alcohol consumption, the effect of radiation pollution on the body and other negative environmental factors.
The decrease in hemoglobin can be due to natural factors. For example, in women, the cause of anemia can be the menstrual cycle or pregnancy. Subsequently, the amount of hemoglobin is normalized. A temporary decrease in this indicator is also observed in active donors, who often donate blood. But the increased number of red blood cells is also quite dangerous and undesirable for the body. It leads to an increase in blood density and the formation of blood clots. Often an increase in this indicator is observed in people living in highland areas.
Normalize hemoglobin levels, possibly by eating foods that contain iron. These include liver, tongue, cattle meat, rabbit, fish, black and red caviar. Products of plant origin also contain the necessary trace element, but the iron in them is absorbed much more difficult. These include legumes, buckwheat, apples, molasses, red peppers and greens.
Shape and size
The structure of red blood cells is characterized primarily by their form, which is quite unusual. It really resembles a disk, concave on both sides. This form of red blood cells is not accidental. It increases the surface of red blood cells and provides the most effective penetration of oxygen into them. This unusual form also contributes to an increase in the number of these cells. Thus, in normal 1 cubic mm of human blood contains about 5 million red blood cells, which also contributes to the best gas exchange.
The structure of the red blood cell frog
Scientists have long established that human red blood cells have structural features that ensure the most efficient gas exchange. This applies to the form, quantity, and internal content. This is especially obvious when comparing the structure of red blood cells of a person and a frog. In the latter, red blood cells are oval and contain a nucleus. This significantly reduces the content of respiratory pigments. Red blood cells of a frog are much larger than human ones, therefore their concentration is not so high. For comparison: if a person has more than 5 million of them in cubic mm, then in amphibians this figure reaches 0.38.
The structure of human erythrocytes and frogs allows to draw conclusions about the evolutionary transformations of such structures. Respiratory pigments are also found in the simplest ciliates. In the blood of invertebrates, they are contained directly in the plasma. But this greatly increases the density of blood, which can lead to the formation of blood clots inside the vessels. Therefore, over time, evolutionary transformations went in the direction of the emergence of specialized cells, the formation of their biconcave form, the disappearance of the nucleus, a decrease in their size and an increase in concentration.
Ontogenesis of red blood cells
The erythrocyte, the structure of which has a number of characteristic features, retains its viability for 120 days. Further their destruction in a liver and a spleen follows. The main blood-forming organ of the person is the red bone marrow. The formation of new erythrocytes from stem cells continuously takes place in it. Initially, they contain a nucleus, which, as it matures, is destroyed and replaced by hemoglobin.
Features of blood transfusion
In a person’s life, there are often situations in which a blood transfusion is required. For a long time, such operations led to the death of the sick, but the real reasons for this remained a mystery. Only at the beginning of the 20th century it was established that the erythrocyte was to blame for everything. The structure of these cells determines the human blood group. There are only four of them, and they are distinguished by the AB0 system.
Each of them is distinguished by a special type of protein substances contained in red blood cells. They are called agglutinogens. People with the first blood group are absent. With the second - have agglutinogens A, with the third - B, with the fourth - AB. At the same time, the blood plasma contains agglutinin proteins: alpha, betta, or both. The combination of these substances determines the compatibility of blood groups. This means that the simultaneous presence in the blood of agglutinogen A and agglutinin alpha is impossible. In this case, the red blood cells stick together, which can lead to the death of the organism.
What is the Rh factor
The structure of the human erythrocyte determines the execution of another function - the definition of the Rh factor. This feature is also necessarily taken into account during blood transfusion. In Rh-positive people on the erythrocyte membrane is a special protein. Most of these people in the world - more than 80%. In Rh - negative people do not have such a protein.
What is the danger of mixing blood with red blood cells of different types? During pregnancy, an Rh-negative woman can get fetal proteins in her blood. In response, the mother's body will begin to produce protective antibodies that neutralize them. During this process, the erythrocytes of the Rh-positive fetus are destroyed. Modern medicine has created special drugs to prevent this conflict.
Red blood cells are red blood cells, the main function of which is to transport oxygen from the lungs to cells and tissues and carbon dioxide in the opposite direction. This role is possible due to the biconcave form, small size, high concentration and the presence of hemoglobin in the cell.