Revision 42567 of "April 1, 2002" on enwiki

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|[[image:spleen1.png|thumb|The visceral surface of the spleen.]]
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|[[image:spleen2.png|thumb|Transverse section of the spleen, showing the trabecular tissue and the splenic vein and its tributaries.]]
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||[[image:spleen3.png|thumb|Transverse section of the human spleen, showing the distribution of the splenic artery and its branches.]]
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||[[image:spleen4.png|thumb|Section of the spleen, showing the termination of the small bloodvessels.]]
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The '''spleen''' is a [[Ductless gland|ductless]], [[vertebrata|vertebrate]] [[gland]] that is not necessary for life but is closely associated with the [[circulatory system]], where it functions in the destruction of old [[red blood cell]]s and removal of other debris from the  bloodstream, and also in holding a reservoir of blood.  It is regarded as one of the centres of activity of the [[reticuloendothelial system]]. Until recently, the purpose of the spleen was not known. It may be removed [[surgery|surgically]] (known as a [[splenectomy]]), and indeed often is.  The spleen is often removed, for example, following abdominal injuries with rupture and [[haemorrhage]] of the spleen, or in the treatment of certain [[blood diseases]] ([[haemorrhagic purpura]], [[familial jaundice]], hereditary [[spherocytosis]], etc.), or for the removal of splenic tumours or cysts. 

It is an  [[organ (anatomy)|organ]] derived from [[mesenchyme]] and lying in the [[mesentery]]. The organ consists of masses of [[lymphoid]] [[biological tissue|tissue]] of granular appearance located around fine terminal branches of [[vein]]s and [[artery|arteries]]. These vessels are connected through the splenic pulp by modified [[capillary|capillaries]] called splenic sinuses. Cross sections of the spleen reveal a red soft surface which is divided into red and white pulp. Red pulp corresponds to the sinuses which are usually filled with [[blood]]. The white pulp shows white nodules, called [[Malpighian corpuscle]]s. Under the microscope, these areas correspond to lymphoid follicles, rich in [[B cell|B-lymphocytes]], and the periarteriolar lymphoid sheaths, rich in [[T cell|T-lymphocytes]].    

The [[human]] spleen is located in the upper left part of the [[abdomen]], behind the [[stomach]] and just below the [[diaphragm (anatomy)|diaphragm]]. In a normal individual this organ measures about 125 × 75 × 50 mm (5 × 3 × 2 in) in size. In certain diseases it often increases in size, and it may even fill a large portion of the left side of the abdomen. Enlargement of the spleen, also known as [[splenomegaly]], occurs in many diseases and disorders, including [[malaria]], [[bacterial endocarditis]], [[leukaemia]], [[pernicious anaemia]], [[Hodgkin's disease]], [[Banti's disease]], [[tumour]]s and [[cyst]]s of the spleen, glandular fever ([[mononucleosis]]), and hereditary [[spherocytosis]].

Congenital abnormalities such as accessory spleens occur, and rarely the spleen has been found to be completely absent. [[Sickle cell anaemia|Sickle-cell disease]] can cause a functional [[asplenia]] by causing infarctions in the spleen during repeated sickle-cell crises.

In certain animals such as [[dog]]s and [[horse]]s, the spleen sequesters a large number of [[erythrocyte|erythrocytes]] (red blood cells), which can be dumped into the bloodstream during periods of physical exertion.  These animals also have large hearts in relation to their body size to accommodate the higher-viscosity blood that results.  Some athletes have tried [[doping (sport)|doping]] themselves with their own stored red blood cells to try to achieve the same effect, but the human [[heart]] is not equipped to handle the higher-viscosity blood.

== Origin ==
The word '''spleen''' comes from the [[Greek language|Greek]] ''splēn''.

In [[French_language|French]], spleen refers to a state of pensive sadness or [[melancholy]]. It has been popularized by the poet [[Charles-Pierre Baudelaire]] ([[1821]]-[[1867]]) but was already used before, in particular in the [[Romanticism|Romantic]] literature ([[18th century]]). The connection between ''spleen'' (the organ) and ''[[melancholy]]'' (the temperament) comes from the [[The four humours|humoral medicine]] of the ancient Greeks. One of the humours (body fluid) was the black [[Bile_(biology)|bile]], secreted by the spleen organ and associated with melancholy. In contrast, the [[Talmud]] (tractate Berachoth 61b) refers to the spleen as the organ of [[laughter]], possibly suggesting a link with the [[The four humours|humoral]] view of the organ.

In [[German language|German]], the word "spleen", pronounced as in English, refers to a persisting somewhat cranky (but not quite lunatic) idea or habit of a person; however the organ is called "Milz". In 19th century England women in bad humour were said to be afflicted by spleen, or the vapours of spleen.

{{lymphatic_system}}
[[Category:Hematology]]

[[da:Milt]]
[[de:Milz]]
[[es:Bazo]]
[[eo:Lieno]]
[[fr:Rate]]
[[ja:脾臓]]
[[pl:Śledziona]]
[[pt:Baço]]

[[Category:Lymphatic system]]
[[Category:Cardiovascular system]]