Blood Groups and Blood Types

Once the clot forms, it consolidates (tightens) to pull the edges of the damaged vessel together.
Vitamin K is needed for normal clot formation although it is not directly involved. It is used in the synthesis of 4 clotting factors.
Small, unwanted clots are usually dissolved by plasmin (fibrinolysin).

Blood is characterized into different blood groups based on the presence or absence of glycoprotein and glycolipid antigens (agglutinogens) on the surface of red blood cells.
There are 24 blood groups and more than 100 antigens
Because these antigens are genetically controlled, blood types vary among different populations.
Classification is based on antigens labeled A, B or AB with O being the absence of the antigens.
An additional antigen, Rh, is present in 85% of humans.