About 5 liters of blood circulate continuously in the body of an adult. From the heart, it is carried throughout the body by a fairly extensive vascular network. The heart needs about a minute, or 70 beats, to let all the blood flow through, which supplies all parts of the body with vital elements.
How does the circulatory system work?
It delivers the oxygen received by the lungs and the nutrients produced in the digestive tract to where they are needed. Blood also transports hormones to the destination and stimulates the removal of decay products from the body. In the lungs it is enriched with oxygen, and carbon dioxide leaves it into the air when a person exhales. It transfers the decay products of cells to the organs of excretion. In addition, the blood ensures that the body always remains uniformly warm. If a person has cold legs or arms, it means that he has insufficient blood supply.
Red blood cells and white blood cells
These are cells with their own special qualities and "tasks." Red blood cells (red blood cells) form in the bone marrow and are constantly updated. There are 5 million red blood cells in 1 mm 3 of blood. Their task is to deliver oxygen to different cells of the whole body. White blood cells - white blood cells (6-8 thousand in 1 mm 3 ). They inhibit the causative agents of diseases that have entered the body. When white bodies themselves are affected by the disease, the body loses its protective functions, and a person can die even from a disease such as flu, which can be quickly dealt with with a normal defense system. The white blood cells of an AIDS patient are affected by the virus - the body can no longer resist disease itself. Each cell, white blood cell or erythrocyte is a living system, and all processes occurring in the body are displayed on its vital functions.
What does blood type mean?
The composition of the blood is different in people, like the appearance, color of hair and skin. How many blood types are there? There are four of them: O (I), A (II), B (III) and AB (IV). The blood group contained in red blood cells and plasma is affected by the type of blood group.
Protein antigens in red blood cells are called agglutinogens. Plasma proteins are called agglutinins. Agglutinogens exist of two types: A and B, agglutinins are also subdivided - a and c.
This is what happens. Take 4 people, for example, Andrei, Alla, Alexei and Olga. Andrei has blood type A with agglutinogens A in the cells and agglutinins in the plasma. Alla has group B: agglutinogens B and agglutinins a. Alexey has an AB group: the peculiarities of 4 blood groups are that agglutinogens A and B are present in it, but there are no agglutinins at all. Olga has a group O - she does not have agglutinogens at all, but agglutinins a and b are in the plasma. Each organism behaves with other agglutinogens as a foreign aggressor.
Compatibility
If Andrei with group A is transfused with the blood of group B, her agglutinins will not accept a foreign substance. These cells will not be able to move freely throughout the body. This means that they will not be able to deliver oxygen to organs such as the brain, and this is life threatening. The same thing happens if you connect A and B groups. Substances B are repelled by substances A, and for O (I) groups both A and B are not suitable. To prevent errors, patients are pre-tested for blood type before transfusion. People who have blood type I are considered the best donors - it will suit anyone. How many blood groups exist - all of them positively perceive blood of group O, it does not contain agglutinogens in red blood cells that might not be liked by the rest. Such people (as in our case Olga) are universal donors. Group AB contains both A- and B-proteins, it can combine with the rest. Therefore, a patient with 4 blood groups (AB), with the necessary transfusion, can safely receive any other. That is why people like Alexey are called universal consumers.
Nowadays, when trying to transfuse a patient, they try to use exactly the blood group that the patient has, and only in urgent cases can the universal first be used. In any case, they must first be checked for compatibility so as not to harm the patient.
What is a Rhesus factor?
The red bodies of some people contain a protein called the Rh factor, so they have a positive Rh factor. About those who do not have such a protein, they say that they have a negative Rh factor, and they are allowed to transfuse only exactly the same blood. Otherwise, their immune system will reject it after the first transfusion.
It is very important to determine the Rh factor during pregnancy. If the mother has a second negative group, and the father has a positive one, the child can inherit the Rh factor of the father. In this case, antibodies accumulate in the mother’s blood, which can lead to the destruction of red blood cells. The second positive group of the fetus creates a Rhesus conflict, which is dangerous for the life and health of the child.
Genetic transmission of the group
Just like a shade of hair, a person will inherit blood from his parents. But this does not mean at all that the child will have the same composition as that of both or any of the parents. Sometimes this question of ignorance becomes the cause of family quarrels. In fact, blood inheritance obeys certain laws of genetics. To understand which and how many blood groups exist when a new life is formed, the table below will help.
For example, if the mother has blood of 4 groups, and the father has the first, the child will not have the same blood as the mother. According to the table, he can have both the second and the third group.
Inheritance of a blood type by a child:
| Maternal blood type | Blood type father |
I | II | III | IV |
I | I | I, II | I, III | II, III |
II | I, II | I, II | I, II, III, IV | II, III, IV |
III | I, III | I, II, III, IV | I, III | II, III, IV |
IV | II, III | II, III, IV | II, III, IV | II, III, IV |
| Possible genetic options in a child |
The Rh factor is also inherited. If, for example, both or one of the parents has a second positive group, then the baby can be born with both positive and negative Rhesus. If each of the parents has a negative Rhesus, then the laws of heredity work. A child may have a first or second negative group.
Dependence on the origin of man
How many blood groups exist, what is their ratio among different nations, depends on the place of their origin. In the world, so many people pass the blood group test, which made it possible for researchers to track how the frequency of one or another varies depending on geographic location. In the United States, 41% of Caucasians have blood of group A, compared with 27% of African Americans. Almost all Indians in Peru have group I, and in Central Asia, group III is the most common. Why these differences exist is not completely understood.
Susceptibility to certain diseases
But scientists noticed some interesting relationships between blood cells and some diseases. Holders of blood type I, for example, are more at risk for ulcer disease. And people who have the second group are at risk of developing stomach cancer. This is very strange, but the proteins that determine the composition of the blood are very similar to the proteins located on the surface of individual pathogenic bacteria and viruses. If a person becomes infected with a virus with surface proteins similar to his own, the immune system can perceive them as his own and allow them to multiply freely.
For example, the surface proteins of microorganisms that cause bubonic plague are very similar to proteins of the first blood group. Scientific researchers suspect that such people may be especially susceptible to this infection. Scientists believe that the disease arose in Southeast Asia and spread to the west. When it reached Europe, it destroyed a quarter of its population in the XIV century: then the disease was called "black death." In Central Asia, the smallest population with blood type I lives. Consequently, it was precisely such a group that was a “flaw” in areas where the plague was especially rampant, and people with other groups were more likely to survive. Scientists believe that there is a dependence of diseases on the composition of the blood. Studying this version will help in the future to decipher the genesis of ailments and reveal the secrets of the survival of mankind.