spleen

1. 1. A large, highly vascular lymphoid organ, lying in the human body to the left of the stomach below the diaphragm, serving to store blood, disintegrate old blood cells, filter foreign substances from the blood, and produce lymphocytes.
   2. A homologous organ or tissue in other vertebrates.
2. Obsolete. This organ conceived as the seat of emotions or passions.
3. Ill temper: vent one's spleen.
4. Archaic. Melancholy.
5. Obsolete. A whim; a caprice.

[Middle English splen, from Old French esplen, from Latin splēn, from Greek.]

An organ of the circulatory system present in most vertebrates, lying in the abdominal cavity usually in close proximity to the left border of the stomach.

In humans the spleen normally measures about 1 by 3 by 5 in. (2.5 × 7.5 × 12.5 cm) and weighs less than ½ lb (230 g). It is a firm organ with an oval shape and is indented on its inner surface to form the hilum, or stalk of attachment to the peritoneum. This mesentery fold also carries the splenic artery and vein to the organ.

The spleen is an important part of the blood-forming, or hematopoietic, system; it is also one of the largest lymphoid organs in the body and as such is involved in the defenses against disease attributed to the reticuloendothelial system. Although the chief functions of the spleen appear to be the production of lymphocytes, the probable formation of antibodies, and the destruction of worn-out red blood cells, other less well-understood activities are known. For example, in some animals it may act as a reservoir for red blood cells, contracting from time to time to return these cells to the bloodstream as they are needed. In the fetus and sometimes in later life, the spleen may be a primary center for the formation of red blood cells. Another function of the spleen is its role in biligenesis. Because the spleen destroys erythrocytes, it is one of the sites where extrahepatic bilirubin is formed. See also Bilirubin; Spleen disorders.

The spleen was linked in past centuries to a variety of emotions, characteristics, or behaviours — usually spitefulness, bad temper, or melancholy, but also sometimes to general liveliness and explosive wit. In the seventeenth century Shakespeare provided many a quote, including the tag ‘spleeny Lutheran’. In the eighteenth century we have Addison's ‘touchy testy pleasant fellow’ with ‘so much Wit and Mirth and Spleen’, whilst less positively a ‘touch of the spleen’ was what we would now call psychosomatic illness. In the late nineteenth century the concept still survived in such whimsies as Gilbert's in Patience: ‘… a sentimental passion of a vegetable fashion must excite your languid spleen’. And ‘venting one's spleen’ has traditionally described a vituperative outburst.

There seems no good reason why the spleen should have deserved these associations — unlike, say, the heart which manifests its link with love by an increase in beating rate with excitement. The spleen is physiologically and anatomically unobtrusive. It is in fact — unusually in the body for an unpaired organ — dispensible. We can live without it because its functions can be taken over elsewhere. It is a small spongy purple mass in a fibrous capsule, tucked under the left side of the diaphragm (smaller than the liver which is tucked under the right side).

The spleen is in a way a poor relation among organs in that it is rarely in the public eye — not even on the butcher's counter. It is not susceptible to dramatic televisual imaging and it does not invite transplantation. It does however sometimes need to be removed: it can suffer hidden injury, for example in crushing or road traffic accidents, when its rupture can cause internal bleeding; other causes for splenectomy include some blood diseases.

Although we can do without it if necessary, the spleen does normally have important functions. In fetal life it is the site of red blood cell formation, until this is taken over by the bone marrow. It contributes to the immune system, forming antibodies and producing and storing masses of lymphocytes. It contains extensive channels and spaces (sinuses) where the blood flows slowly and where senescent red blood cells break down and are removed from the circulation. It therefore becomes enlarged in some infective, parasitic, and blood diseases.

The spleen acts to some extent as a blood reservoir, although this mechanism for increasing circulating blood volume is relatively minor and unimportant in humans compared with some other animals. The smooth muscle in its capsule is activated by the autonomic nervous system in conditions of ‘fight or flight’ or after blood loss, squirting a little extra blood into the circulation — which is perhaps the nearest physiological equivalent to the metaphoric ‘venting’.

— Sheila Jennett

See lymphatic system. See also blood; humours; immune system.

Gland near the stomach with main function of destroying ‘worn-out’ red blood cells and recycling the iron. As a food it is called melts; A 150-g portion of calf spleen is a rich source of iron, vitamins B₂, niacin, and C; a good source of vitamin A; contains 6 g of fat; supplies 150 kcal (630 kJ).

The most commonly injured organ within the abdomen. The spleen lies just below the 9th and 11th ribs, making it very susceptible to puncture by a fractured rib or a direct blow to the trunk. It can even be ruptured during a non-contact sport as a result of very strenuous activity, especially if it has become enlarged by a viral infection (in athletes, nearly 40 per cent of splenic ruptures are associated with glandular fever caused by a viral infection called infectious mononucleosis). This is one of several important reasons for resting during a fever.

The spleen has a number of functions, including removing worn out red blood cells and dealing with some types of foreign body. In order to carry out these functions, it is very well supplied with blood, making it quite soft and fragile. A rupture often results in torrential internal bleeding which is difficult to stop. If untreated, this can lead to a serious lowering of blood pressure and death. Sometimes bed rest is sufficient treatment, but often surgical removal is the only viable course of action. Abdominal injuries are often underestimated in sports, especially when young people with enormous reserves of enthusiasm are involved. Consequently, a ruptured spleen may go unnoticed and untreated until the injured person loses so much blood he or she suffers from potentially fatal shock. Abdominal injuries are very difficult to diagnose, but expert medical assistance should always be sought if a person is suffering from persistent abdominal discomfort after a blow or after extreme exertion.

noun

A tendency to become angry or irritable: irascibility, irascibleness, temper, temperament, tetchiness. Informal dander. Slang short fuse. Idioms: low boiling point. See feelings.

A soft, highly vascular, roughly ovoid organ situated between the stomach and the diaphragm in the left hypochondriac region of the body. It is considered part of the lymphatic system.

For more information on spleen, visit Britannica.com.

A large, highly vascularized organ situated beneath the stomach. It is part of the reticuloendothelial system producing white blood cells, and removing worn out red blood cells and some foreign bodies. It is the most commonly injured organ in the abdomen. Its position just below the ninth and eleventh ribs makes it very susceptible to puncture by a fractured rib or a direct blow to the trunk. It can even be ruptured during a non-contact sport as a result of very strenuous activity, especially if it has become enlarged during a viral infection. About 40% of sport-related splenic ruptures are associated with infectious mononucleosis, emphasizing the need to avoid strenuous activity during the febrile stage of an illness. A splenic rupture often results in massive internal bleeding, which can lead to a potentially fatal lowering of blood pressure. Usually, surgical removal of the spleen is the only viable course of action. Splenic ruptures can easily go unnoticed. Expert medical assistance should be sought whenever an athlete is suffering from persistent abdominal discomfort after a blow or extreme physical exertion.

An organ in the lymphatic system, in the upper left part of the abdomen, that filters out harmful substances from the blood. The spleen also produces white blood cells, removes worn-out red blood cells from circulation, and maintains a reserve blood supply for the body.

A large lymphoid organ usually situated in the cranial part of the abdominal cavity on the left of the stomach. The spleen contains the largest collection of reticuloendothelial cells in the body. In ruminants the spleen is located on the left lateral wall of the reticulum and under the last two ribs on the left side. Called also lien.

• accessory s. — a small mass of tissue, histologically and functionally identical with that composing the normal spleen but found elsewhere in the body.
• slaughter s. — see slaughter spleen.

For other uses, see Spleen (disambiguation).

Spleen
Spleen
Laparoscopic view of a horse's spleen (the purple and grey mottled organ)
Latin	splen, lien
Gray's	subject #278 1282
Artery	Splenic artery
Vein	Splenic vein
Nerve	Splenic plexus
Precursor	Mesenchyme of dorsal mesogastrium
MeSH	Spleen
Dorlands/Elsevier	Spleen

The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system^[1] In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells, holds a reserve in case of hemorrhagic shock, especially in animals like horses (not in humans) and recycles iron.^[2] It synthesizes antibodies in its white pulp, removes from the circulation antibody-coated bacteria and antibody-coated blood cells.^[2][3] Recently it has been found to contain in reserve half the body's monocytes in its red pulp that upon moving to injured tissue such as the heart turn into dendritic cells and macrophages and aid wound healing.^[4][5][6] It is one of the centers of activity of the reticuloendothelial system, and can be considered analogous to a large lymph node. Its absence leads to a predisposition to certain infections.^[7]

Contents 1 Anatomy 2 Function 3 Effect of removal 4 Disorders 5 Etymology and cultural views 6 Variation among vertebrates 7 See also 8 Additional images 9 Footnotes 10 External links

Anatomy

Spleens in healthy adult humans are approximately 11 centimetres (4.3 in) in length. It usually weighs 150 grams (5.3 oz) and lies beneath the 9th to the 12th rib.^[8]

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.^[9]

The spleen is unique with 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 ^[10]. 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.

Function

Area	Function	Composition
red pulp	Mechanical filtration of red blood cells. Reserve of monocytes[4]	"sinuses" (or "sinusoids") which are filled with blood "splenic cords" of reticular fibers "marginal zone" bordering on white pulp
white pulp	Active immune response through humoral and cell-mediated pathways.	Composed of nodules, called Malpighian corpuscles. These are composed of: "lymphoid follicles" (or "follicles"), rich in B-lymphocytes "periarteriolar lymphoid sheaths" (PALS), rich in T-lymphocytes

Other functions of the spleen are less prominent, especially in the healthy adult:

• Production of opsonins, properdin, and tuftsin.

• Creation of red blood cells. While the bone marrow is the primary site of hematopoeisis in the adult, the spleen has important hematopoietic functions up until the fifth month of gestation. After birth, 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.^[11] In humans, it does not act as a reservoir of blood cells.^[12] It can also store platelets in case of an emergency.

• Storage of half the body's monocytes so that upon injury they can migrate to the injured tissue and transform into dendritic cells and macrophages and so assist wound healing.^[4]

Effect of removal

See also: Asplenia

Surgical removal causes:^[5]

• modest increases in circulating white blood cells and platelets,
• diminished responsiveness to some vaccines,
• increased susceptibility to infection by bacteria and protozoa

A 28 year follow up of 740 veterans of World War II found that those who had been splenectomised showed a significant excess mortality from pneumonia (6 from expected 1.3) and ischaemic heart-disease (41 from expected 30) but not other conditions.^[13]

Disorders

Main article: 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

The word spleen comes from the 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.^[14]

In 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 in the 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 humoral medicine of 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 humoral view of the organ. In 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 "splenetic" is used to describe a person in a foul mood.

In Chinese, 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," "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 mainly regarding digestion, which in some scholars' opinions corresponds to the function of the pancreas. Spleen is also the formal name for an elite social group with headquarters in South Georgia.

Variation among vertebrates

In 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 serosal lining of the intestine. In many amphibians, especially frogs, it takes on the more rounded form, and there is often a greater quantity of white pulp.^[15]

In reptiles, birds, and mammals, 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.^[15]

The only vertebrates to lack a spleen are the lampreys and hagfishes. 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 homologous with the spleen of higher vertebrates.^[15]

See also

• Marginal zone

Additional images

The celiac artery and its branches.	The celiac artery and its branches.	Horizontal disposition of the peritoneum in the upper part of the abdomen.	Transverse section through the middle of the first lumbar vertebra.
The duodenum and pancreas.	The visceral surface of the spleen.	Transverse section of the spleen, showing the trabecular tissue and the splenic vein and its tributaries.	Transverse section of the human spleen, showing the distribution of the splenic artery and its branches.
Section of the spleen, showing the termination of the small blood vessels.	Back of lumbar region, showing surface markings for kidneys, ureters, and spleen.	Side of thorax, showing surface markings for bones, lungs (purple), pleura (blue), and spleen (green).	Lymphatic system

Footnotes

1. ^ Spleen, Internet Encyclopedia of Science
2. ^ ^{a b} Mebius RE, Kraal G. (2005). Structure and function of the spleen. Nat Rev Immunol. 5(8):606-16. PMID 16056254
3. ^ Loscalzo, Joseph; Fauci, Anthony S.; Braunwald, Eugene; Dennis L. Kasper; Hauser, Stephen L; Longo, Dan L. (2008). Harrison's principles of internal medicine. McGraw-Hill Medical. ISBN 9780071466339. 
4. ^ ^{a b c} 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
5. ^ ^{a b} Jia T, Pamer EG. (2009). Dispensable But Not Irrelevant. Science, 325:549-550. doi:10.1126/science.1178329
6. ^ Finally, the Spleen Gets Some Respect By NATALIE ANGIER, New York Times, August 3, 2009
7. ^ Brender, MD, Erin; Allison Burke, MA, illustrator, Richard M. Glass, MD, editor (2005-11-23). "Spleen Patient Page" (PDF). Journal of the American Medical Association (American Medical Association) 294 (20): 2660. http://jama.ama-assn.org/cgi/reprint/294/20/2660.pdf. Retrieved 2008-03-20. 
8. ^ Spielmann, Audrey L.; David M. DeLong, Mark A. Kliewer (01 Jan 2005). "Sonographic Evaluation of Spleen Size in Tall Healthy Athletes". American Journal of Roentgenology (American Roentgen Ray Society) 2005 (184): 45–49. PMID 15615949. http://www.ajronline.org/cgi/content/abstract/184/1/45. Retrieved 2008-09-09. 
9. ^ thefreedictionary.com - penicilliary radicles
10. ^ Vellguth, Swantje; Brita von Gaudecker, Hans-Konrad Müller-Hermelink. "The development of the human spleen". Cell and Tissue Research (Springer Berlin / Heidelberg) 242 (3): 579–592. http://www.springerlink.com/content/q231303t1455j524/. Retrieved 2009-02-14. 
11. ^ Carey, Bjorn (May 5, 2006). "Horse science: What makes a Derby winner - Spleen acts as a 'natural blood doper,' scientist says". MSNBC.com (Microsoft). http://www.msnbc.msn.com/id/12648465/. Retrieved 2006-05-09. 
12. ^ Tao Le. First Aid for the Basic Sciences: General Principles. Page 460.
13. ^ 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
14. ^ Robertson's Word Pictures of the New Testament, commentary on 1 Peter 3:8
15. ^ ^{a b c} Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 410-411. ISBN 0-03-910284-X. 

External links

Look up spleen in Wiktionary, the free dictionary.

• SUNY Figs 38:03-01 - "The visceral surface of the spleen."
• SUNY Anatomy Image 7881
• "spleen" from Encyclopedia Britannica Online
• Spleen and Lymphatic System, Kidshealth.org (American Academy of Family Physicians)
• Spleen Diseases from MedlinePlus
• Finally, the Spleen Gets Some Respect New Times piece upon the spleen

v • d • e Immune system: Lymphatic system (Lymph, Lymphocytes, Lymph vessels) (TA A13.1-2, GA 8) Primary Bone marrow · Thymus (Hassall's corpuscles) Secondary Spleen (process blood) structural: Hilum · Trabeculae Red pulp (Cords of Billroth, Marginal zone) White pulp (Periarteriolar lymphoid sheaths, Germinal center) blood flow: Trabecular arteries · Trabecular veins Lymph nodes (process extracellular fluid) lymph flow: Afferent lymph vessels · Cortical sinuses · Medullary sinuses · Efferent lymph vessels T cells: High endothelial venules B cells: Primary follicle/Germinal center · Mantle zone · Marginal zone layers: Capsule/Trabeculae · Subcapsular sinus · Cortex · Paracortex · Medulla (Medullary cord) · Hilum MALT (process mucosa) GALT · Peyer's patches · Germinal center lymphatic organ navs: anat, physio, lymphatic disease/splenic disease/thymus disorders/thymus neoplasia/vascular tumors, proc

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Dansk (Danish)
n. - milt, tungsind, dårligt humør, spleen, livslede

Nederlands (Dutch)
milt, boosheid

Français (French)
n. - (Anat) rate, (fig) mauvaise humeur, spleen

Deutsch (German)
n. - Milz, Zorn

Ελληνική (Greek)
n. - (ανατ.) σπλήνα, (μτφ.) μελαγχολία, κακοκεφιά, οργή

Italiano (Italian)
milza

Português (Portuguese)
n. - baço (m), mau humor (fig.)

Русский (Russian)
селезенка, злоба, недоброжелательство, раздражительность

Español (Spanish)
n. - bazo

Svenska (Swedish)
n. - mjälte, dåligt humör, svårmod, mjältsjuka

中文（简体）(Chinese (Simplified))
脾脏, 怨恨, 坏脾气

中文（繁體）(Chinese (Traditional))
n. - 脾臟, 怨恨, 壞脾氣

한국어 (Korean)
n. - 비장, 악의 , 낙담

日本語 (Japanese)
n. - 脾臓, 腹立ち

العربيه (Arabic)
‏(الاسم) الطحال, حنق, غضب شديد‏

עברית (Hebrew)
n. - ‮טחול, דכדוך, כעס, זעם‬

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