Spleen

Spleen

The spleen (from Greek --?—spl?n[1]) is an organ found in virtually all vertebrate animals. Similar in structure to a large lymph node, the spleen acts primarily as a blood filter. As such, it is a non-vital organ, with life possible after removal. The spleen plays important roles in regard to red blood cells (also referred to as erythrocytes) and the immune system.[2] In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock while also recycling 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 subsequently shuttled to the liver for removal.[3] It synthesizes antibodies in its white pulp and removes antibody-coated bacteria along with antibody-coated blood cells by way of blood and lymph node circulation. The spleen is brownish in color.[3][4] A study published in 2009 using mice showed it has been found to contain in its reserve half of the body's monocytes within the red pulp.[5] These monocytes, upon moving to injured tissue (such as the heart), turn into dendritic cell

and macrophages while promoting tissue healing.[5][6][7] It is one of the centers of activity of the reticuloendothelial system and can be considered analogous to a large lymph node, as its absence leads to a predisposition toward certain infections. The spleen, in healthy adult humans, is approximately 11 centimetres (4.3 in) in length. It usually weighs between 150 grams (5.3 oz)[9] and 200 grams (7.1 oz).[10] 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. Like the thymus, the spleen possesses only efferent lymphatic vessels. The spleen is part of the lymphatic system. Both the short gastric arteries and the splenic artery supply it with blood.[11] The germinal centers are supplied by arterioles called penicilliary radicles.[12] The spleen is unique in respect to its development within the gut. While most of the gut viscera are endodermally derived (with the exception of the neural-crest derived suprarenal gland), the spleen is derived from mesenchymal tissue.[13] Specifically, the spleen forms within, and from, the dorsal mesentery. However, it still shares the same blood supply—the celiac trunk—as the foregut organs.