What Is the Function of Blood Cells?


Blood cells are vital to the human body. There are three types of blood cells; red blood cells, white blood cells and platelets. These microscopic cells are responsible for many things. The three basic functions of blood cells are to transport oxygen throughout the body, fight infection and to stop bleeding.

Red Blood Cells

Red blood cells, also known as erythrocytes, are the main transporters of oxygen throughout the body. These cells contain no nucleus and only live about 120 days. They are small, doughnut-shaped cells that contain the pigment hemoglobin, which gives the cells their reddish color and assists the cells in carrying oxygen and carbon dioxide. The erythrocytes circulate throughout the body, bringing oxygen to the tissues and picking up carbon dioxide, the waste product formed in the cells.

White Blood Cells

White blood cells or leukocytes are larger than erythrocytes. The main function of leukocytes is to fight against injury and disease, making them a major part of the body’s immune system. There are five types of leukocytes: neutrophils, eosinophils, basophils, lymphocytes and monocytes. Leukocytes destroy bacteria in the body by engulfing and digesting them during phagocytosis. They also work to wall off infected areas of the body and to dispose of remnants from inflammation sites. White blood cells increase in number when there is an allergic reaction or infection in the body.


Platelets, also known as thrombocytes, are the smallest of the blood cells. They are really just fragments of cells, not complete cells. The main job of thrombocytes is to start the blood-clotting process. These cells react to a wound by stimulating the damaged vessel to produce sticky structures that the platelets can attach to, creating a platelet plug to stop bleeding. The thrombocytes also secret a chemical that causes the blood vessel to constrict until a clot can form.


Normal blood cells perform these functions with no difficulty. However, it is possible for there to be abnormalities in the cells that can cause physical difficulties. Sickle cell anemia causes red cells to form in a crescent shape, which decreases their oxygen-carrying ability. Polycythemia is a condition where too many red cells are formed, causing a thickening of the blood. Thrombocytopenia is a condition where there is a decrease in platelets, which doesn't allow blood to clot.


Blood tests can be run for a variety of different diseases. The number of blood cells present in a sample of blood can speak volumes. Different types of anemia maybe diagnosed based on the number or shape of erythrocytes. The amount of certain types of leukocytes can show allergic reactions, infection, inflammation or injury. The amount of platelets found in a sample can be indicative of how well a person will clot after a cut or wound, especially useful to know prior to surgery.

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  • Body Structures & Functions; Ann Senisi Scott; 2004
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