|MadSci Network: Immunology|
The spleen, located in the left upper quadrant of the abdomen, generally weighs about 135 grams (4.8 ounces) in an average-sized adult. As you noted, it has several functions, including destruction of old blood cells (particularly red blood cells), participation in the immune response, and under certain circumstances, production of new blood cells (especially in the fetus and in certain disease states where the function of the bone marrow is impaired).
The average lifespan of a red blood cell is 60 days. At the end of its life, it generally gets engulfed and destroyed by macrophages. Under normal circumstances, this process of phagocytosis takes place for the most part in the spleen, which serves as an efficient filter to trap worn-out red blood cells and "present" them to macrophages. However, this process can also occur in the liver and bone marrow, and these sites can take over the entire job after splenectomy (removal of the spleen). It is interesting to note that the average lifespan of a red blood cell does not increase in splenectomized patients, suggesting that old red blood cells can still be culled efficiently from the circulation in the absence of the spleen.
Thanks for your question!
Stephen C. Lattanzi, M.D.
New London Cancer Center, Inc.
1. LaCelle PL. Destruction of erythrocytes. In: Williams WJ et al. Hematology. Edition 4. New York City: McGraw-Hill, 1990. pp. 398-407.
2. Tavassoli M. Structure and function of the spleen. Ibid. pp. 54-62.
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