Blood is used by the body for transportation of oxygen, food, waste products, and other materials within the body. It is also used for regulation of body temperature, regulation of fluids, and acid-base equilibrium. Because blood is used for multiple functions within the body, tests on the blood or its components may give valuable clues in the diagnosis of a multitude of medical conditions.
Blood is made up of a fluid portion (plasma) and a cellular portion. Plasma contains various substances dissolved in the fluid. Serum is what remains when fibrinogen has been removed from the plasma (this is the fluid that remains after blood is allowed to clot in a test tube). The cellular portion consists primarily of red blood cells, but also includes white blood cells and platelets.
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