Blood is divided into groups based onpresence in it of certain antigens and antibodies to them. There are four main groups: 0 (I), A (II), B (III), and also AB (IV). Each of them corresponds to a number, and the letter indicates the absence or presence of specific antigens. This is also an indicator of compatibility.
The most common blood type is the first. For transfusion, it is the most suitable, because it does not contain antigens. The second is only suitable for people of the same and the fourth group because of the presence of antigens A. The third is suitable only for the owners of the third and fourth, and the last of them can be transfused only to people with the same blood group.
However, the importance is not only the presence of eitherabsence of antigens, but also Rh factor. It is determined by the presence of protein on the surface of erythrocytes. If it is, the Rh factor is positive, and if it is absent, it is negative. About 85% of the world's population have a positive Rh factor. For example, the third negative blood group is much less common than the positive one. The same goes for the rest.
Group and Rhesus should be considered duringplanning of pregnancy. If the fetus inherits the parameters of the father, which will be incompatible with the blood of the mother, then during pregnancy problems are possible. However, modern medicine is quite capable of preventing them.
The composition of the blood was formed many thousands of years andis associated with the formation of the immune and digestive systems. Blood group 1 was positive in ancient times for all mankind. The digestive tract was then most suitable for digesting meat protein foods.
For example, blood-holders with a gene A aremore adapted to life in the modern world. This gene in its time became a guarantee of survival of people during the terrible epidemics of plague and cholera. People with this blood composition are less aggressive and have more contact, which helps them feel good in society.</ p>