Blood

Blood is a liquid tissue that distributes substances to all the cells enabling contact between different parts of the body. Human blood (mammalian blood) consist of plasma and blood cells: erythrocytes (red blood cells), leukocytes (white blood cells) and thrombocytes (platelets). Red blood cells distribute oxygen, white blood cells are important element of the immune system and platelets take part in blood coagulation.

Proteins from the red blood cells’ surface states blood types. When mixing different blood types those proteins became antigens and cause immune response. For the main blood type (AB0) antibodies against antigens not found in own cells are present in everybody’s blood. For other blood types antibodies are produces only after exposure to the antigen.