In humans, the blood is an essential component that functions in the transportation of vital substances to and from the body, regulation of internal mechanisms and defense against foreign particles that invade the body. The primary constituents of blood include plasma, red blood cells, white blood cells and platelets.
In 1901, the Austrian scientist Karl Landsteiner identified the ABO blood group. This discovery vastly improved the success of medical blood transfusions. The ABO blood group comprises four blood types: A, B, AB and O. Each blood type is determined by the presence or absence of antigens and antibodies. Antibodies are found in the blood plasma while antigens are attached to the surface of the red blood cells. When different blood types are combined, the antigens from one type bind to the antibodies of the other type, which results to clumping or agglutination. The clumped blood may constrict the blood vessels and prevent the proper circulation of blood. Agglutination may also trigger the red blood cells to rupture and spill their hemoglobin content, which becomes poisonous once outside the cell and may even cause the death of the individual.Learn more about Blood