K. Landsteiner classified human blood into four groups in 1902 AD. These groups are A, B, AB and O. Blood group O is called universal blood donor because blood of O group can be given to any of the other groups. Similarly blood group "AB" is called universal blood acceptor because it accepts blood from all blood groups.
Blood clotting or coagulation is a process which stops the flow of blood from some injury. An insoluble protein called fibrin is essential for blood clotting. The person suffering from "Haemophilia" has a problem in blood clotting. The flowing blood does not stop easily. The Ph value of the blood is 7-4 and it is basic in nature.
Rh factor is a blood antigen found in R.B.C. of J blood. The persons who have Rh factor in themselves are called RH+ and the persons do not have Rh factor in themselves are called RH.
A normal person has blood pressure of 80 mm of Hg. The heartbeat of a normal person is 70-72 per MINUTE.