Blood is very important for human beings as well as animals as it performs several functions. The most important function of blood are carrying oxygen to and away from the heart.
Secondly, blood helps in carrying wastes from the body to the excretory system. The human blood is made up of plasma and cells (red, white and platelets). 90% of the plasma is made up of water and salts. Blood contains 55% of plasma and 45% of cells.
However, there are also different types of proteins present in the blood known as antigens. Depending on the presence of antigens, blood can be classified into different types or groups.
What are Blood Groups?
Blood groups were first developed and put forth by an Austrian scientist known as Karl Landsteiner in 1901. He is also credited for the discovery of the Rh (Rhesus) factor present in the blood. Landsteiner classified blood into 4 types, viz., A, B, AB, and O.
The classification was made on the basis of presence of the respective antigen in blood. For e.g., if the blood contains an antigen A, the blood group of the person is A. Based on this rule, the blood type or group of all people in the world can be determined at the time of the birth.
Secondly, another factor, known as the Rh (Rhesus) factor is also important for determining the exact blood type of the person. Rh stands for Rhesus, which comes from the name of the Rhesus monkey as this protein was found in the monkey's body.
Presence of the Rhesus factor D determines whether the blood type of the person is positive or negative. Therefore, according to this theory, if a person's blood contains antigen A along with Rhesus factor D, his blood type becomes A+. On the other hand, if a person blood contains antigen A and does not contain Rhesus factor D, his blood type is A-.
Based on both the aforementioned theories, blood types or blood groups in the world can be categorized into 8 different types, viz., A+, A-, B+, B-, AB+, AB-, O+, and O-. It is very essential to know ones' blood types in order to undergo safe blood transfusion.
Secondly, in early times, the difference of Rh factors between parents' blood types used to cause life-threatening condition in babies. However, today there are medications available that help in preventing this.
Most Common Blood Group
Common blood types are the Rhesus factor positive types like A+, B+, AB+, and O+. When compared with their respective negative counterparts, the percentage of the positive blood types is more than that of the negative ones. That is, nearly 85% of the world population have Rhesus positive blood type, while only a mere 15% have Rhesus negative blood type.
Among the 8 types, O+ is the most common blood type. Nearly 35-40% people all over the world have O+ blood type. The second most common type is the A+ with 30-32% people belonging to it all over the world.
As O+ is a common blood type, people belonging to this group have no problems in receiving as well as donating blood. However, with the advancement of techniques in blood transfusions and availability of blood banks, there has been a decrease in the number of problems related to it.