Lymphoid organ, located in the left side of the abdomen behind the stomach. The spleen is the primary filtering element for the blood, and it is a storage site for red blood cells (erythrocytes) and platelets. It is one of four places where reticuloendothelial cells are found (see reticuloendothelial system). Two types of tissue, red pulp and white pulp, are intermixed. The white pulp is lymphoid tissue containing lymphocyte production centres. The red pulp is a network of channels filled with blood where most of the filtration occurs and is the major site of destruction of deteriorating erythrocytes and recycling of their hemoglobin. Both contain cells (see leukocyte) that remove foreign material and initiate an antibody-producing process. The spleen becomes enlarged in some infections. Its rupture in high-impact injuries may require surgical removal, which leaves the patient more susceptible to overwhelming infection.
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