Spleen

The spleen is a ductless, vertebrateglandthat is not necessary for life but is closely associated with the circulatory system, where it functions in the destruction of old red blood cellsand 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 is increasingly recognised that its absence predisposes to certain infections.

Anatomy

It is an organderived from mesenchymeand lying in the mesentery. The organ consists of masses of lymphoidtissueof granular appearance located around fine terminal branches of veinsand arteries. These vessels are connected through the splenic pulp by modified capillariescalled 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 corpuscles. Under the microscope, these areas correspond to lymphoid follicles, rich in B-lymphocytes, and the periarteriolar lymphoid sheaths, rich in T-lymphocytes.

The humanspleen is located in the upper left part of the abdomen, behind the stomachand just below the diaphragm. In a normal individual this organ measures about 125 × 75 × 50 mm (5 × 3 × 2 in) in size.

In certain animals such as dogsand horses, the spleen sequesters a large number of 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 dopingthemselves with their own stored red blood cells to try to achieve the same effect, but the human heartis not equipped to handle the higher-viscosity blood.

Approximately 10% of people have one or more accessory spleens. They may form near the hilumof the main spleen, the junction at which the splenic vessels enter and leave the organ.

Disorders

Enlargement of the spleen is known as splenomegaly. It may be caused by malaria, bacterial endocarditis, leukaemia, pernicious anaemia, leishmaniasis, Hodgkin's disease, Banti's disease, hereditary spherocytosis, cysts, glandular fever (mononucleosis), and tumours. Primary tumours of the spleen include hemangiomasand hemangiosarcomas. Marked splenomegaly may result in the spleen occupying large portion of the left side of the abdomen.

Absence

The absence of a spleen predisposes to some septicaemiainfections. Vaccination and antibiotic measures are discussed under asplenia.

• Some people congenitallycompletely lack a spleen, although this is rare.

• Sickle-cell diseasecan cause a functional asplenia(or autosplenectomy) by causing infarctionsof the spleen during repeated sickle-cell crises.

• It may be removed surgically(known as a splenectomy), and indeed often is. For example, it may be removed following abdominal injuries with rupture and hemorrhageof the spleen, or in the treatment of certain blood diseases(Idiopathic thrombocytopenic purpura, familial jaundice, hereditary spherocytosis, etc.), certain forms of lymphomaor for the removal of splenic tumours or cysts.

Etymology and cultural views

The word spleen comes from the Greeksplēn.

In 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 Romanticliterature (18th century). The connection between spleen (the organ) and melancholy (the temperament) comes from the humoral medicineof the ancient Greeks. One of the humours (body fluid) was the black 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 humoralview of the organ.

In 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", (cognate with Old Englishmilte). In 19th century England women in bad humour were said to be afflicted by spleen, or the vapours of spleen. In modern English "to vent one's spleen" means to vent one's anger, e.g. by shouting, and can be applied to both males and females.

In China, the spleen '? (pi2)' counts as the seat of one's temperament. Analogous to "venting one's spleen", "???" is used as an expression.

de:Milz es:Bazo eo:Lieno fr:Rate it:Milza he:???? lt:Blu?nis nl:Milt ja:?? pl:?ledziona pt:Baço ru:????????? scn:Meusa fi:Perna vi:Lách zh:??

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It uses material from the http://en.wikipedia.org/wiki/Spleen Wikipedia article Spleen.