Why are there four types of human blood?
people did not always have different types of blood, but rather evolved to have them in response to disease over time. The reason why individual people have different types of blood is that they inherit the feature of their blood, who have certain antigens on the outside of the blood cells from their parents. Antigens are molecules that cause an immune response. In fact, there are more than four types of blood - International Blood Transfusion Society (ISBT) recognizes 29 different blood groups systems that include more than 600 different antigens. However, the most famous and medically useful system of blood groups, called ABO, distinguishes four types of blood.
Not all types of human blood have always existed. In fact, they developed over time due to genetic changes and mutations. It is assumed that type A is the oldest type of blood, which then mutated 3.5 million years ago to type B. About a million years later, the type of the type developed. Some people also have a type of AB blood that has antigens A and B. The reason why blood has changed is considered to be consideredThe response to the sick-type O is to be more resistant to malaria and many people in the areas susceptible to malaria have o o.
ABO types of blood are important because the blood of a different type than its own can cause a fatal immune response if it is introduced into the body. Along with the antigens on red blood cells, the body carries an antibody in the immune system that recognizes and fights antigens in foreign blood. The ABO system deals with the presence or absence of two specific antigens called A and B.
red blood cells may have antigens A or B or both antigens A and B, or neither. Blood only with antigens is classified as type A, while blood with only b antigens is type B. Blood with antigens A and B is classified as AB type and blood with no antigen type O.
The immune system has antibodies that protect against antigens that are not present in their own blood. Those whoThey have blood type A, have anti-B antibodies; Blood B has anti-A antibodies; AB blood has no one of these antibodies and people with blood types have both. Patients cannot receive blood transfusions from donors whose blood contains antigen, which does not have their own blood, because their antibodies begin defense against it. Ideally, the donor and the recipient in the blood transfusion should have the same blood type. However, if this is not possible, other combinations are safe.
type O Blood is known as a "universal donor". Since it carries neither antigens nor B, it may exist in the presence of anti-A and anti B antibodies and is therefore compatible with any recipient's blood type. On the contrary, people type O can only receive blood from another type.
type AB Blood is also called "a vicile of universal income."Em. Blood types A and B are mutually incompatible for blood transfusions, but both can donate type or receive blood or receive blood.
The ABO Blood Group is often complemented by a system of Rhesus blood groups. Although this system deals with five specific antigens, according to the presence or absence of antigen D: RHD negative and RHD positive. Those with blood types in the ABO system are sometimes considered to be positive or negative, as with "negative type", because negative recipients of RHD are not compatible with RHD positive donors.