An organ that removes and destroys worn-out red blood cells and helps fight infection . The spleen is covered with a capsule from which many fibrous bands run inward to give the organ a sponge-like structure.
Blood is supplied to the spleen by a large artery that branches extensively within the organ.
One of the two main functions of the spleen is to control the quality of circulating red blood cells. It accomplishes this by removing and breaking down all worn-out red cells approximately 120 days after they have been produced in the bone marrow and by destroying other red cells that are misshapen or defective . The other role of the spleen is to help fight infection by producing some of the antibodies , phagocytes, and lymphocytes that destroy invading microorganisms . In the fetus , the spleen produces red blood cells. After birth, this function is taken over by the bone marrow.