What Is Blood and What Does It Do

Blood is a red “liquid tissue “ and makes up seven percent of our body weight. Blood has two functions: it brings oxygen and nutrients to all cells and receives carbon dioxide and waste substances from them. For 55 percent , blood is made up of plasma, a mixture of water and protein . In plasma there are mainly three types of cells: red blood cells, white blood cells and platelets . 

Blood under a microscope

Blood is not the same in all individuals : scientists have determined that there are 4 blood groups called A, B, AB and 0 (zero) . The blood of each of us belongs to one of these groups. Some groups are not compatible with each other and therefore, when a blood transfusion is necessary, one must know the group of the donor and that of the recipient, to avoid serious consequences 

What are the functions of blood?
• transport of substances in all areas of the body (except epidermis and its derivatives: hair, hair, nails, tooth enamel and cornea without blood vessels);
• defense against everything that enters our body and is not recognized as its own and is therefore foreign, including pathogenic microorganisms – viruses, bacteria, fungi;
• repair of damage and wounds to the blood vessels through blood coagulation to avoid bleeding;
• distribution of the heat generated mainly by muscle contraction through the control of peripheral circulation: if we are hot we become red because vasodilation occurs, if we are cold a vasoconstriction occurs.


Plasma can be separated from whole blood by removing red blood cells, white blood cells and platelets. This is accomplished by centrifuging the blood at high speed. The corpuscular parts rest on the bottom of the container and it is therefore possible to drain the plasma from the surface.

Most people know the donation of whole blood, a painless procedure that lasts only about ten minutes (in addition to the time required for preparation and recovery). But it is also possible to donate plasma, and only plasma, through a procedure called plasmapheresis. During plasmapheresis, blood is drawn, plasma is separated, while red blood cells and platelets are re-infused to the donor. Usually the process takes about 45 minutes and the plasma regenerates quickly.

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