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The spleen (from Greek —''splḗn''〔) is an organ found in virtually all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The spleen plays important roles in regard to red blood cells (also referred to as erythrocytes) and the immune system.〔(Spleen ), Internet Encyclopedia of Science〕 It removes old red blood cells and holds a reserve of blood, which can be valuable in case of hemorrhagic shock, and also recycles iron. As a part of the mononuclear phagocyte system, it metabolizes hemoglobin removed from senescent erythrocytes. The globin portion of hemoglobin is degraded to its constitutive amino acids, and the heme portion is metabolized to bilirubin, which is removed in the liver. The spleen synthesizes antibodies in its white pulp and removes antibody-coated bacteria and antibody-coated blood cells by way of blood and lymph node circulation. A study published in 2009 using mice found that the spleen contains, in its reserve, half of the body's monocytes within the red pulp. These monocytes, upon moving to injured tissue (such as the heart), turn into dendritic cells and macrophages while promoting tissue healing.〔〔(Finally, the Spleen Gets Some Respect ) By NATALIE ANGIER, The New York Times, August 3, 2009〕 The spleen is a center of activity of the mononuclear phagocyte system and can be considered analogous to a large lymph node, as its absence causes a predisposition to certain infections. In humans, the spleen is brownish in color and is located in the left upper quadrant of the abdomen.〔 ==Structure== The spleen, in healthy adult humans, is approximately to in length. It usually weighs between 〔(eMedicine > Splenomegaly ) Author: David J Draper. Coauthor(s): Ronald A Sacher, Emmanuel N Dessypris, Lewis J Kaplan. Updated: Oct 4, 2009〕 and . An easy way to remember the anatomy of the spleen is the 1×3×5×7×9×11 rule. The spleen is 1" by 3" by 5", weighs approximately 7 oz, and lies between the 9th and 11th ribs on the left hand side. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spleen」の詳細全文を読む スポンサード リンク
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