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| − | {{Copyedited}}{{Approved}}{{Images OK}}{{Submitted}}{{Paid}}
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| − | {{Infobox Anatomy |
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| − | Name = {{PAGENAME}} |
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| − | Latin = splen, lien |
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| − | GraySubject = 278 |
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| − | GrayPage = 1282 |
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| − | Image = Illu spleen.jpg |
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| − | Caption = Spleen |
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| − | Image2 = Horse_spleen_laparoscopic.jpg |
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| − | Caption2 = [[Laparoscopic]] view of a horse's spleen. (The purple and gray mottled organ). |
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| − | Precursor = [[Mesenchyme]] of [[dorsal mesogastrium]] |
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| − | System = |
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| − | Artery = [[Splenic artery]] |
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| − | Vein = [[Splenic vein]] |
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| − | Nerve = [[Splenic plexus]] |
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| − | Lymph = |
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| − | MeshName = Spleen |
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| − | MeshNumber = A10.549.700 |
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| − | DorlandsPre = s_19 |
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| − | DorlandsSuf = 12750780 |
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| − | }}
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| − | The '''spleen''' is a vascular [[lymphatic system|lymphoid]] [[organ (anatomy)|organ]] found in most [[vertebrate]]s, normally close to the stomach in the abdominal cavity, and that functions in various activities related to the [[circulatory system]] and the [[immune system]]. The spleen is involved in filtering [[blood]] of foreign invaders and old [[red blood cell]]s (erythrocytes), destruction of old red blood cells and recycling [[hemoglobin]], storing blood and holding a reservoir of red blood cells, producing [[lymphocyte]]s, sometimes serving as a center for forming red blood cells, and possibly forming [[antibody|antibodies]]. It is regarded as one of the centers of activity of the [[reticuloendothelial system]] (part of the immune system).
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| − | As with other parts of the body ([[cell (biology)|cells]], [[tissue]]s, other organs, and organ systems), the spleen provides larger benefit to the body and likewise is dependent on other organs, as well as cells, tissues, and organ systems, for its own proper functioning. This principle whereby each body part provides some benefit to the whole and to other body parts, while also receiving benefit, underlies the complex coordination and harmony seen in organisms.
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| − | Until recently, the purpose of the spleen was not known. Historically, it was considered the seat of passion or emotion, and thus the phrase "vent one's spleen."
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| − | It is increasingly recognized that its absence leads to a predisposition to certain [[infection]]s.
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| − | == Human spleen: Anatomy and physiology==
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| − | The [[human being|human]] spleen is located in the upper left part of the [[abdomen]], behind the [[stomach]] and just below the [[diaphragm (anatomy)|diaphragm]]. In normal individuals, this organ measures about 125 by 75 by 50 millimeters (5 by 3 by 2 inches) in size, with an average weight of 150 grams.
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| − | The spleen is the largest [[organ (anatomy)|organ]] derived from [[mesenchyme]] and lying in the [[mesentery]]. It consists of masses of [[lymphatic system|lymphoid]] [[tissue]] of granular appearance located around fine terminal branches of [[vein]]s and [[artery|arteries]]. These vessels are connected by modified [[capillary|capillaries]] called splenic sinuses.
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| − | Approximately ten persent of people have one or more accessory spleens. They may form near the [[hilum]] of the main spleen, the junction at which the splenic vessels enter and leave the organ.
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| − | There are several [[peritoneal]] [[ligament]]s that support the spleen:
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| − | * gastrolienal ligament (gastrosplenic) - connects stomach to spleen.
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| − | * lienorenal ligament (splenorenal) - connects spleen to kidney.
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| − | * phrenicocolic ligament - connects left colic flexure to the thoracic diaphragm.
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| − | To understand this terminology, it helps to know that "lien" is an alternate root for "spleen."
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| − | Cross sections of the spleen reveal a red soft surface, which is divided into two types of pulp which correspond to the two most important functional roles of the spleen, summarized below:
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| − | {| class="wikitable"
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| − | | '''Area''' || '''Composition''' || '''Function'''
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| − | | Red pulp || Composed of:<BR>* "[[sinus]]es" (or "sinusoids"), which are filled with [[blood]]<BR>* "[[splenic cords]]" of [[reticular fiber]]s<BR>* "marginal zone" bordering on white pulp || Mechanical filtration. Removes unwanted materials from the blood, including senescent [[red blood cell]]s.
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| − | |-
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| − | | White pulp || Composed of nodules, called [[Malpighian corpuscle]]s. These are composed of:<BR>* "lymphoid follicles" (or "follicles"), rich in [[B cell|B-lymphocytes]]<BR>* "periarteriolar lymphoid sheaths" (PALS), rich in [[T cell|T-lymphocytes]] || Helps fight infections.
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| − | |}
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| − | Other functions of the spleen are less prominent, especially in the healthy adult:
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| − | * Production of [[opsonin]]s, [[properdin]], and [[tuftsin]].
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| − | * Creation of [[red blood cell]]s. While the [[bone|bone marrow]] is the primary site of hematopoeisis (formation of blood cells) in the adult, up until the fifth month of gestation, the spleen has important hematopoietic functions. After birth, no significant hematopoietic function is left in the spleen except in some hematologic disorders: e.g., [[myelodysplastic syndrome]], [[hemoglobinopathy|hemoglobinopathies]].
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| − | In certain [[mammal]]s, not humans, there is another function of the spleen:
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| − | * Storage of red blood cells and other formed elements. This is only valid for some mammals, such as [[dog]]s and [[horse]]s. In horses, roughly 50 percent of the red blood cells are stored there. The red blood cells can be released when needed. In humans, however, the spleen does not function as a deposit of red blood cells, but instead it stores platelets in case of an emergency (Carey 2006). 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 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.
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| − | == Disorders ==
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| − | Enlargement of the spleen is known as ''splenomegaly''. It may be caused by [[malaria]], [[sarcoidosis]], infectious mononucleosis, bacterial endocarditis, [[leukemia]], [[pernicious anemia]], Gaucher's disease, leishmaniasis, or Hodgkin's disease]]. Splenomegaly diagnosis involves a complete blood count with differential, platelet count, and reticulocyte and atypical [[lymphocyte]] counts to exclude hemolytic anemia and leukemia. Assessment of [[Antibody#IgM|IgM]] [[antibody|antibodies]] to viral capsid [[antigen]] (a rising titer) is indicated to confirm Epstein-Barr virus or cytomegalovirus. Other infections should be excluded if these tests are negative.
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| − | The absence of a spleen predisposes to some septicemia infections.
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| − | * Some people congenitally completely lack a spleen, although this is rare.
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| − | * [[Sickle-cell disease]] can cause a functional [[asplenia]] (lack of normal spleen function) or autosplenectomy (when a disease causes lack of normal spleen function, as if removed surgically) by causing infarctions of the spleen during repeated sickle-cell crises.
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| − | * The spleen may be removed [[surgery|surgically]] (known as a splenectomy), and indeed often is. For example, it may be removed following abdominal injuries with rupture and [[hemorrhage]] of the spleen, or in the treatment of certain blood diseases (Idiopathic thrombocytopenic purpura, hereditary spherocytosis, etc.), certain forms of [[lymphoma]] or for the removal of splenic tumors or cysts.
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| − | == Etymology and cultural views==
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| − | The word '''spleen''' comes from the [[Greek language|Greek]] ''splēn''.
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| − | 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 [[Romanticism|Romantic]] literature (eighteenth century). The connection between ''spleen'' (the organ) and ''melancholy'' (the temperament) comes from the humoral medicine of the ancient Greeks. One of the humors (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 humoral view of the organ.
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| − | 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 English milte). In nineteenth-century England, women in bad humor were said to be afflicted by spleen, or the vapors 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.
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| − | In [[China]], the spleen 脾 (pí) counts as the seat of one's temperament and is thought to influence the individual's willpower. Analogous to "venting one's spleen" (发脾气) is used as an expression for getting angry, although in the view of traditional Chinese medicine, the view of "脾" does not correspond to the anatomical "spleen."
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| − | ==Additional images==
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| − | <gallery>
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| − | Image:Gray532.png|The celiac artery and its branches.
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| − | Image:Gray533.png|The celiac artery and its branches.
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| − | Image:Gray1039.png|Horizontal disposition of the peritoneum in the upper part of the abdomen.
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| − | Image:Gray1097.png|Transverse section through the middle of the first lumbar vertebra.
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| − | Image:Gray1098.png|The duodenum and pancreas.
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| − | image:Gray1188.png|The visceral surface of the spleen.
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| − | image:Gray1189.png|Transverse section of the spleen, showing the trabecular tissue and the splenic vein and its tributaries.
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| − | image:Gray1190.png|Transverse section of the human spleen, showing the distribution of the splenic artery and its branches.
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| − | image:Gray1192.png|Section of the spleen, showing the termination of the small bloodvessels.
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| − | image:Gray1226.png|Back of lumbar region, showing surface markings for kidneys, ureters, and spleen.
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| − | image:Gray1217.png|Side of thorax, showing surface markings for bones, lungs (purple), pleura (blue), and spleen (green).
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| − | Image:Illu lymphatic system.jpg|The lymphatic system.
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| − | </gallery>
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| − | ==Reference==
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| − | * Barcroft, J., H. A. Harris, D. Orahovats, and R. Weiss. 1925. “A Contribution to the Physiology of the Dpleen. ''J Physiol.'' 60(5-6): 443–456.
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| − | * Barcroft, J., and J. G. Stephens. 1927. “Observations Upon the Size of the Spleen.” ''J Physiol.'' 64(1): 1–22.
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| − | * Carey, B. 2006. [http://www.msnbc.msn.com/id/12648465/ “Horse Science: What Makes a Derby Winner.”] MSNBC.com (May 5, 2006). Retrieved September 11, 2007.
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| − | * McCance, R. A., and E. M. Widdowson. 1955. “The Size and Function of the Spleen in Young Puppies. ''J Physiol.'' 129(3): 636–638.
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| − | {{lymphatic_system}}
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| − | {{credit|129600245}}
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| − | [[Category:Life sciences]]
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| − | [[Category:Anatomy and physiology]]
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