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 levels.
Erythrocyte: structure and function
The circulatory system of man and mammalian animals is characterized by the most perfect structure in comparison with other organisms. It consists of a four-chambered heart and a closed system of blood vessels, through which blood continuously circulates. This tissue consists of a liquid component - plasma, and a number of cells: erythrocytes, leukocytes and platelets. Every cell plays a role. The structure of human erythrocyte is due to the functions performed. This concerns the size, shape and quantity of these blood cells.
Features of the structure of erythrocytes
Erythrocytes have the form of a biconcave disk. They are not able to move independently in the bloodstream, like leukocytes. To tissues and internal organs they come through the work of the heart. Erythrocytes are prokaryotic cells. This means that they do not contain a formal kernel. Otherwise, they could not carry oxygen and carbon dioxide. This function is performed due to the presence inside the cells of a special substance - hemoglobin, which also determines the red color of the human blood.
Structure of hemoglobin
The structure and functions of red blood cells are largely due to the peculiarities of this particular substance. Two components make up hemoglobin. This is an iron-containing component called gem, and protein globin. The first time to decipher the spatial structure of this chemical compound was succeeded by the English biochemist Max Ferdinand Perutz. For this discovery in 1962 he was awarded the Nobel Prize. Hemoglobin is the representative of a group of chromoproteins. These include complex proteins, consisting of a simple biopolymer and prosthetic group. For hemoglobin this group is heme. This group also includes plant chlorophyll, which ensures the process of photosynthesis.
How is gas exchange
In humans and other chordates, 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 makes it possible to form unstable compounds with oxygen and carbon dioxide. Blood, saturated with oxygen, is called arterial. It is enriched with this gas in the lungs.
From the aorta, she goes to the arteries, and then - to the capillaries. These smallest vessels are suitable for every cell in the body. Here the red blood cells give off oxygen and attach the main product of respiration - carbon dioxide. With the flow of blood, which is already venous, they come back into the lungs. In these organs gas exchange occurs in the smallest vesicles - the alveoli. Here, hemoglobin disconnects carbon dioxide, which is removed from the body by exhalation, and the blood is again saturated with oxygen.
Such chemical reactions are due to the presence of ferrous iron in the heme. As a result of the compound and decomposition, oxy- and carbhemoglobin are successively formed. But a complex protein of red blood cells can form and persistent connections. For example, with incomplete combustion of fuel, carbon monoxide is released, which forms hemoglobin with carboxyhemoglobin. This process leads to the death of erythrocytes and poisoning of the body, which can lead to death.
What is anemia?
Shortness of breath, palpable weakness, noise in the ears, noticeable pallor of the skin and mucous membranes may indicate an insufficient amount of hemoglobin in the blood. The norm of its content varies depending on sex. In women, this figure is 120 - 140 g per 1000 ml of blood, and for men it reaches 180 g / l. The content of hemoglobin in the blood of newborns is greatest. It exceeds this figure in adults, reaching 210 g / l.
Lack of hemoglobin is a serious disease, which is called anemia or anemia. It can be caused by a lack of vitamins and iron salts in foods, an addiction to alcohol, the effect of radiation pollution and other negative environmental factors on the body.
Reducing the amount of hemoglobin can be due to natural factors. For example, in women, the cause of anemia may be a 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 an increased amount of red blood cells is also quite dangerous and undesirable for the body. It leads to an increase in the density of blood and the formation of blood clots. Often, this increase is observed in people living in high-altitude areas.
Normalize the hemoglobin level by eating foods containing iron. These include the liver, tongue, meat of cattle, rabbit, fish, black and red caviar. Vegetable products also contain the necessary trace element, but the iron found in them is much more difficult to digest. These include fruits of legumes, buckwheat, apples, molasses, red peppers and herbs.
Shape and size
The structure of blood erythrocytes is characterized primarily by their form, which is quite unusual. It really looks like a disk, concave from both sides. This form of red blood cells is not accidental. It increases the surface of erythrocytes and provides the most effective penetration of oxygen in them. Such an unusual form contributes to an increase in the number of these cells. So, in norm in 1 cubic mm of human blood contains about 5 million erythrocytes, which also contributes to the best gas exchange.
Structure of red blood cells of a frog
Scientists have long established that human red blood cells have structural features that provide the most effective gas exchange. This concerns both form, quantity, and internal content. This is especially obvious when comparing the structure of red blood cells of a human and a frog. In the latter, red blood cells have an oval shape and contain a nucleus. This significantly reduces the content of respiratory pigments. Erythrocytes of frogs are much larger than human, therefore their concentration is not so high. For comparison: if a person has more than 5 million in cubic mm, then this figure reaches 0.38 for amphibians.
Evolution of red blood cells
The structure of human and frog erythrocytes makes it possible to draw conclusions about the evolutionary transformations of such structures. Respiratory pigments are also found in the simplest infusoria. 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 have moved toward 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
Erythrocyte, whose structure has a number of characteristic features, retains viability for 120 days. Subsequently, their destruction in the liver and spleen. The main human blood-forming organ is the red bone marrow. It continuously generates new red blood cells from stem cells. Initially, they contain a nucleus that, as it ripens, is destroyed and replaced by hemoglobin.
Features of blood transfusion
In a person's life, situations often arise that require blood transfusions. For a long time such operations led to the death of patients, and the real reasons for this remained a mystery. Only at the beginning of the 20th century it was established that the fault was due to the erythrocyte. The structure of these cells determines the blood group of a person. There are four in total, but they are distinguished according to the ABO 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 proteins of agglutinin: alpha, betta, or both. The combination of these substances determines the compatibility of blood groups. This means that simultaneous presence in the blood of agglutinogen A and agglutinin alfa is impossible. In this case, the red blood cells stick together, which can lead to the death of the body.
What is the Rh factor
The structure of the human erythrocyte determines the performance of one more function - the determination of the Rhesus factor. This characteristic is also taken into account during blood transfusion. Rhesus-positive people have a special protein on the erythrocyte membrane. There are more than 80% of such people in the world. Rhesus - negative people have no such protein.
What is the danger of mixing blood with red blood cells of different types? During the pregnancy of the Rh-negative woman, fetal proteins can penetrate into her blood. In response, the mother's body will begin to develop protective antibodies that neutralize them. During this process, the red blood cells of the Rh-positive fetus are destroyed. Modern medicine has created special drugs that prevent this conflict.
Erythrocytes are red blood cells, the main function of which is the transfer of oxygen from the lungs to cells and tissues and carbon dioxide in the opposite direction. This role is possible thanks to biconcave form, small size, high concentration and the presence of hemoglobin in the cell.