View source for Spleen

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{{Infobox Anatomy |
  Name         = Spleen |
  Latin        = splen, lien |
  GraySubject  = 278 |
  GrayPage     = 1282 |
  Image        = Illu spleen.jpg |
  Caption      = Spleen |
  Image2       = Horse_spleen_laparoscopic.jpg |
  Caption2     = [[Laparoscopic]] view of a horse's spleen (the purple and grey mottled organ) |
  Precursor    = [[Mesenchyme]] of [[dorsal mesogastrium]] |
  System       = |
  Artery       = [[Splenic artery]] |
  Vein         = [[Splenic vein]] |
  Nerve        = [[Splenic plexus]] |
  Lymph        = |
  MeshName     = Spleen |
  MeshNumber   = A10.549.700 |
  Dorlands = seven/000099557 |
  DorlandsID = Spleen

}}
The '''spleen''' (from [[Greek language|Greek]] "σπλήν" - ''splen''<ref>[http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dsplh%2Fn σπλήν],
Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus Digital Library</ref>) is an organ found in virtually all [[vertebrate]] animals with important roles in regard to [[red blood cells]] and the [[immune system]].<ref name="all-vert">[http://www.daviddarling.info/encyclopedia/S/spleen.html Spleen], [[Internet Encyclopedia of Science]]</ref> 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 [[Shock (circulatory)|hemorrhagic shock]] while also recycling [[Human iron metabolism|iron]].<ref name="Mebius">Mebius RE, Kraal G. (2005). Structure and function of the spleen. Nat Rev Immunol. 5(8):606-16. PMID 16056254</ref> 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 purple and gray.<ref name="Mebius"/><ref name="isbn9780071466339">{{cite book |author=Loscalzo, Joseph; Fauci, Anthony S.; Braunwald, Eugene; Dennis L. Kasper; Hauser, Stephen L; Longo, Dan L. |title=Harrison's principles of internal medicine |publisher=McGraw-Hill Medical |location= |year=2008 |pages= |isbn=9780071466339 |oclc= |doi= |accessdate=}}</ref> Recently, it has been found to contain in its reserve half of the body's [[monocyte]]s within the [[red pulp]]. These monocytes, upon moving to injured tissue (such as the heart), turn into [[dendritic cell]]s and [[macrophage]]s while promoting tissue healing.<ref name="Swirski">Swirski FK, Nahrendorf M, Etzrodt M, Wildgruber M, Cortez-Retamozo V, Panizzi P, Figueiredo J-L, Kohler RH, Chudnovskiy A, Waterman P, Aikawa E, Mempel TR, Libby P, Weissleder R, Pittet MJ. (2009). Identification of Splenic Reservoir Monocytes and Their Deployment to Inflammatory Sites. Science, 325: 612-616. {{DOI|10.1126/science.1175202}}</ref><ref name="Jia">Jia T, Pamer EG. (2009). Dispensable But Not Irrelevant. Science, 325:549-550. {{doi|10.1126/science.1178329}}</ref><ref>[http://www.nytimes.com/2009/08/04/science/04angier.html Finally, the Spleen Gets Some Respect] By NATALIE ANGIER, New York Times, August 3, 2009</ref> 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 [[infection]]s.<ref name="certain-infec">{{cite journal
  | last = Brender, MD
  | first = Erin
  | author = Erin Brender, MD
  | coauthors = Allison Burke, MA, illustrator, Richard M. Glass, MD, editor
  | title = Spleen Patient Page
  | journal = [[Journal of the American Medical Association]]
  | volume = 294
  | issue = 20
  | pages = 2660
  | publisher = [[American Medical Association]]
  | date = 2005-11-23
  | url = http://jama.ama-assn.org/cgi/reprint/294/20/2660.pdf
  | format = PDF
  | accessdate = 2008-03-20 }}</ref>

== Anatomy ==
<!--(Put anatomy here)-->

The spleen, in healthy adult humans, is approximately {{convert|11|cm}} in length. It usually weighs {{convert|200|g}} and lies beneath the 9th to the 12th thoracic ribs.<ref>{{cite journal | last=Spielmann | first=Audrey L. | coauthors=David M. DeLong, Mark A. Kliewer | title=Sonographic Evaluation of Spleen Size in Tall Healthy Athletes | journal=American Journal of Roentgenology | volume=2005 | issue=184 | pages=45–49 | publisher=American Roentgen Ray Society | url=http://www.ajronline.org/cgi/content/abstract/184/1/45 | accessdate=2008-09-09 | pmid=15615949 | date=1 January 2005}}</ref>

Like the [[thymus]], the spleen possesses only [[efferent lymphatic vessels]].

The spleen is part of the lymphatic system.

The [[germinal centers]] are supplied by arterioles called ''penicilliary radicles''.<ref>[http://medical-dictionary.thefreedictionary.com/penicilliary+radicles thefreedictionary.com - penicilliary radicles]</ref>

The spleen is unique in respect to its development within the [[Human gastrointestinal tract|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 [[Mesenchyme|mesenchymal tissue]].<ref>{{cite journal | last= Vellguth | first=Swantje | coauthors=Brita von Gaudecker, Hans-Konrad Müller-Hermelink | title=The development of the human spleen | journal=[[Cell and Tissue Research]] | volume=242 | issue=3 | pages=579–592 | publisher=Springer Berlin / Heidelberg | url=http://www.springerlink.com/content/q231303t1455j524/ | accessdate=2009-02-14 }}</ref> Specifically, the spleen forms within, and from, the [[dorsal mesentery]].  However, it still shares the same blood supply &mdash; the [[celiac trunk]] &mdash; as the [[foregut]] organs.

== Function ==
[[Image:Spleen hyaloserositis - low mag.jpg|thumb|right|[[Micrograph]] of splenic tissue showing the red pulp (red), white pulp (blue) and a [[hyaloserositis|thickened inflamed capusule]] (mostly pink - top of image). [[H&E stain]].]]
{| class="wikitable"
| '''Area''' || '''Function ''' || '''Composition'''
 |-
 | [[red pulp]] || Mechanical filtration of [[red blood cells]]. Reserve of [[monocyte]]s<ref name="Swirski"/> ||
* "[[Sinus (anatomy)|sinuses]]" (or "[[Sinusoid (blood vessel)|sinusoid]]s") which are filled with blood
* "[[splenic cords]]" of [[reticular fiber]]s
* "[[marginal zone]]" bordering on white pulp
 |-
 | [[white pulp]] || Active immune response through humoral and cell-mediated pathways. || Composed of nodules, called [[White pulp|Malpighian corpuscle]]s. These are composed of:<BR>
* "[[lymphoid follicles]]" (or "follicles"), rich in [[B cell|B-lymphocytes]]
* "[[periarteriolar lymphoid sheaths]]" (PALS), rich in [[T cell|T-lymphocytes]]
|}

Other functions of the spleen are less prominent, especially in the healthy adult:
* Production of [[opsonin]]s, [[properdin]], and [[tuftsin]].
* Creation of [[red blood cells]]. While the [[bone marrow]] is the primary site of [[hematopoiesis]] in the adult, the spleen has important hematopoietic functions up until the fifth month of gestation. After birth, [[Erythropoiesis|erythropoietic]] functions cease, except in some hematologic disorders.  As a major lymphoid organ and a central player in the reticuloendothelial system, the spleen retains the ability to produce lymphocytes and, as such, remains an hematopoietic organ.
* Storage of [[red blood cells]] and other formed elements.  In horses roughly 30% of the red blood cells are stored there. The red blood cells can be released when needed.<ref name="MSNBC2006-Carey">{{cite news | first=Bjorn | last=Carey | url=http://www.msnbc.msn.com/id/12648465/ | title=Horse science: What makes a Derby winner - Spleen acts as a 'natural blood doper,' scientist says | work= MSNBC.com | publisher=Microsoft | date=May 5, 2006  | accessdate=2006-05-09}}</ref> In humans, it does not act as a reservoir of blood cells.<ref>Tao Le. First Aid for the Basic Sciences: General Principles. Page 460.</ref>  It can also store [[platelets]] in case of an emergency.
*  Storage of half the body's [[monocyte]]s so that upon injury they can migrate to the injured tissue and transform into [[dendritic cell]]s and [[macrophage]]s and so assist [[wound healing]].<ref name="Swirski"/>

==Effect of removal==
{{See also|Asplenia}}
Surgical removal causes:<ref name="Jia"/>
* modest increases in circulating [[white blood cell]]s and [[platelet]]s,
*diminished responsiveness to some [[vaccine]]s,
* increased susceptibility to infection by [[bacteria]] and [[protozoa]]; in particular, there is an increased risk of sepsis from [[polysaccharide encapsulated bacteria]].

Surgical removal is a fairly non-invasive procedure and, in emergency circumstances, can be removed without anesthetic. A 28-year follow-up of 740 veterans of World War II who had their spleen removed on the battlefield found that those who had been [[splenectomy|splenectomise]]d showed a significant excess of mortality from [[pneumonia]] (6 from an expected 1.3) and a significant excess of mortality from [[ischaemic heart disease]] (4.1 from an expected 3) but not from other conditions.<ref>Robinette CD, Fraumeni JF Jr. (1977). Splenectomy and subsequent mortality in veterans of the 1939-45 war. Lancet. Jul 16;2(8029):127-9. PMID 69206 {{doi|10.1016/S0140-6736(77)90132-5}}</ref>

== Disorders ==
{{Main|Splenic disease}}
Disorders include [[splenomegaly]], where the spleen is enlarged for various reasons, and [[asplenia]], where the spleen is not present or functions abnormally.

== Etymology and cultural views==<!-- This section is linked from [[Gabriel Fauré]] -->
The word '''spleen''' comes from the [[Greek language|Greek]] σπλήν, and is the idiomatic equivalent of the heart in English, i.e. to be good-spleened (εὔσπλαγχνος) means to be good-hearted or compassionate.<ref>Robertson's Word Pictures of the New Testament, commentary on 1 Peter 3:8</ref>

In English the word ''spleen'' was customary during the period of the 18th century. Authors like [[Richard Blackmore]] or [[George Cheyne]] employed it to characterize the hypocondriacal and hysterical affections.<ref>[[George Cheyne|Cheyne, George]]: ''The English Malady; or, A Treatise of Nervous Diseases of All Kinds, as Spleen, Vapours, Lowness of Spirits, Hypochondriacal and Hysterical Distempers with the Author's own Case at large'', Dublin, 1733. Facsimile ed., ed. Eric T. Carlson, M.D., 1976, Scholars' Facsimiles & Reprints, ISBN 9780820112817;</ref><ref>[[Richard Blackmore|Blackmore, Richard]]: ''Treatise of the spleen and vapors''. London, 1725</ref>

In [[French language|French]], "splénétique" refers to a state of pensive sadness or [[melancholy]]. It has been popularized by the poet [[Charles Baudelaire]] (1821–1867) but was already used before in particular to the [[Romanticism|Romantic]] literature (18th century). The word for the organ is "la rate."

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]] while possibly suggesting a link with the [[Humourism|humoral]] view of the organ. In the eighteenth- and nineteenth-century England, women in bad humour were said to be afflicted by the spleen, or the vapours of the 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. Similarly, the English term "[[wikt:splenetic|splenetic]]" is used to describe a person in a foul mood.

In [[Chinese language|Chinese]], the spleen '[[wikt:脾|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", "發脾氣" 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". "脾" is a conceptual functional group that mainly has regards to digestion which, in some scholars' opinions, corresponds to the function of the pancreas.

==Variation among vertebrates==
In [[cartilaginous fish|cartilagenous]] and [[ray-finned fish]] the spleen is normally a somewhat elongated organ, consisting primarily of red pulp, with only a small amount of white pulp. In [[lungfish]], the spleen is not a distinct organ as it actually lies inside the [[serosa]]l lining of the [[intestine]]. In many [[amphibian]]s, especially [[frog]]s, it takes on the more rounded form and there is often a greater quantity of white pulp.<ref name=VB>{{cite book |author=Romer, Alfred Sherwood|author2=Parsons, Thomas S.|year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia, Pennsylvania|pages= 410–411|isbn= 0-03-910284-X}}</ref>

In [[reptile]]s, birds, and [[mammal]]s, white pulp is always relatively plentiful, and in the latter two groups, the spleen is typically rounded, although it adjusts its shape somewhat to the arrangement of the surrounding organs.  In the great majority of vertebrates, the spleen continues to produce red blood cells throughout life; it is only in mammals that this function is lost in the adult. Many mammals possess tiny spleen-like structures known as '''haemal nodes''' throughout the body, which presumably have the same function as the spleen proper.<ref name=VB/> The spleens of aquatic mammals are in some ways dissimilar to those of fully land dwelling mammals. In general the spleens of aquatic mammals are bluish in colour.  In cetaceans and manatees it tends to be quite small, but in deep diving pinnipeds it can be quite massive, owing to its function of storing red blood cells.

The only vertebrates lacking a spleen are the [[lamprey]]s and [[hagfish]]es. Even in these animals, there is a diffuse layer of haematopoeitic tissue within the gut wall, which has a similar structure to red pulp, and is presumably [[homology (biology)|homologous]] with the spleen of higher vertebrates.<ref name=VB/>

==See also==
* [[Marginal zone]]

==Additional images==
<gallery>
 Image:Gray532.png|The celiac artery and its branches.
 Image:Gray533.png|The celiac artery and its branches.
 Image:Gray1039.png|Horizontal disposition of the peritoneum in the upper part of the abdomen.
 Image:Gray1097.png|Transverse section through the middle of the first lumbar vertebra. 
 Image:Gray1098.png|The duodenum and pancreas.
 image:Gray1188.png|The visceral surface of the spleen.
 image:Gray1189.png|Transverse section of the spleen, showing the trabecular tissue and the splenic vein and its tributaries.
 image:Gray1190.png|Transverse section of the human spleen, showing the distribution of the splenic artery and its branches.
 image:Gray1192.png|Section of the spleen, showing the termination of the small blood vessels.
 image:Gray1226.png|Back of lumbar region, showing surface markings for kidneys, ureters, and spleen. 
 image:Gray1217.png|Side of thorax, showing surface markings for bones, lungs (purple), pleura (blue), and spleen (green).
 Image:Illu lymphatic system.jpg|Lymphatic system
</gallery>

==References==
{{Reflist}}

==External links==
{{Wiktionary|spleen}}
* {{SUNYAnatomyFigs|38|03|01}} - "The visceral surface of the spleen."
* {{SUNYAnatomyImage|7|8|81}}
* [http://www.britannica.com/eb/article-9069185/spleen "spleen"] from ''[[Encyclopædia Britannica Online]]''
* [http://www.kidshealth.org/PageManager.jsp?dn=familydoctor&lic=44&cat_id=20091&article_set=20543&ps=104 Spleen and Lymphatic System], Kidshealth.org ([[American Academy of Family Physicians]])
* [http://www.nlm.nih.gov/medlineplus/spleendiseases.html Spleen Diseases] from [[MedlinePlus]]
* [http://www.nytimes.com/2009/08/04/science/04angier.html?hpw "Finally, the Spleen Gets Some Respect"] ''New York Times'' piece on the spleen
{{Anatomy}}
{{lymphatic_system}}

[[Category:Glands]]
[[Category:Abdomen]]
[[Category:Lymphatic system]]
[[Category:Cardiovascular system]]
[[Category:Hematology]]
[[Category:Horse anatomy]]
[[Category:Greek loanwords]]

[[ar:طحال]]
[[an:Mielsa]]
[[arc:ܛܚܠܐ]]
[[az:Dalaq]]
[[bn:প্লীহা]]
[[bs:Slezena]]
[[br:Felc'h]]
[[bg:Слезка]]
[[ca:Melsa]]
[[cv:Сула]]
[[cs:Slezina]]
[[da:Milt]]
[[de:Milz]]
[[dv:ހުންކޮށި]]
[[et:Põrn]]
[[el:Σπλήνας]]
[[es:Bazo]]
[[eo:Lieno]]
[[eu:Bare (organoa)]]
[[fa:طحال]]
[[fr:Rate]]
[[ko:지라]]
[[hi:तिल्ली]]
[[hr:Slezena]]
[[id:Limpa]]
[[is:Milta]]
[[it:Milza]]
[[he:טחול]]
[[pam:Lape]]
[[ka:ელენთა]]
[[la:Lien]]
[[lv:Liesa]]
[[lt:Blužnis]]
[[hu:Lép]]
[[mk:Слезенка]]
[[ml:പ്ലീഹ]]
[[ms:Limpa]]
[[nl:Milt]]
[[ja:脾臓]]
[[no:Milt]]
[[nn:Milt]]
[[pag:Pali]]
[[pl:Śledziona]]
[[pt:Baço]]
[[ro:Splină]]
[[qu:K'ayrapin]]
[[ru:Селезёнка]]
[[scn:Mèusa]]
[[simple:Spleen]]
[[sk:Slezina]]
[[sl:Vranica]]
[[sr:Слезина]]
[[sh:Slezina]]
[[su:Kawaya]]
[[fi:Perna]]
[[sv:Mjälte]]
[[tl:Pali (glandula)]]
[[ta:மண்ணீரல்]]
[[te:ప్లీహము]]
[[th:ม้าม]]
[[tr:Dalak]]
[[uk:Селезінка]]
[[ur:تلی]]
[[ug:تلا]]
[[vi:Lách]]
[[fiu-vro:Põrn]]
[[zh-yue:脾]]
[[zh:脾脏]]
[[Category:2Fix]]