Spleen

From Wikipedia, the free encyclopedia

 This article needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (February 2008)
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 s_19/12750780

The spleen is an organ found in all vertebrate animals[1]. In humans, the spleen is located in the abdomen of the body, where it functions in the destruction of redundant red blood cells and holds a reservoir of blood. It is regarded as one of the centers of activity of the reticuloendothelial system (part of the immune system). It is increasingly recognized that its absence leads to a predisposition to certain infections.[2]

Contents

[edit] Anatomy

The human spleen is located in the upper left part of the abdomen, behind the stomach and just below the diaphragm. In normal individuals this organ measures about 125 × 75 × 50 mm (5 × 3 × 2 inches) in size, with an average weight of 150 grams (5 oz).

The spleen consists of masses of lymphoid tissue of granular appearance located around fine terminal branches of veins and arteries. These vessels are connected by modified capillaries called splenic sinuses.

Approximately 10% 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.

There are several peritoneal ligaments that support the spleen[3] (to understand their naming it helps to know that "lien" is an alternate root for "spleen")

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 in the next section. [4]

[edit] Function

Area Function Composition
red pulp Mechanical filtration. Removes unwanted materials from the blood, including old red blood cells.
white pulp Helps fight infections. Composed of nodules, called Malpighian corpuscles. These are composed of:

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

  • Creation of red blood cells. While the bone marrow is the primary site of hematopoeisis in the adult, up until the fifth month of gestation, the spleen has important hematopoietic functions. 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. This is only valid for certain mammals, such as dogs and horses[citation needed]. In horses roughly 50% of the red blood cells are stored there. The red blood cells can be released when needed [5] These animals also have large hearts in relation to their body size to accommodate the higher-viscosity blood that results. In humans, however, the spleen does not function as a depository of red blood cells, but instead it stores platelets in case of an emergency. Some athletes have tried doping themselves with their own stored red blood cells to try to achieve the same effect[citation needed], but the human heart is not equipped to handle the higher-viscosity blood.

[edit] Disorders

Main article: Splenic disease

Disorders include splenomegaly, where the spleen is enlarged by various reasons. On the other hand, a lack of normal spleen function is called asplenia.

[edit] Etymology and cultural views

The word spleen comes from the Greek splēn. In Latin its name is lien.

In French, spleen 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 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 German, the word "spleen", pronounced as in English, refers to a persisting somewhat eccentric (but not quite lunatic) idea or habit of a person; however the organ is called "Milz", (cognate with Old English milte).

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 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", "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".

In chiropractic (meric chart) problems with the spleen relate to T8 (eighth thorasic vertebrea), a subluxation at T8 is associated with low energy and/or low immune system function.

In infants it is not very common for the spleen to destroy red blood cells faster than the liver can conjugate the bilirubin. The effect of this would be more bilirubin in the blood plasma.

[edit] See also

[edit] 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 bloodvessels.

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

[edit] Footnotes

  1. ^ Entry for spleen, Internet Encyclopedia of Science
  2. ^ Brender, MD, Erin; Richard M. Glass, MD, editor (2005-11-23-30). "Spleen Patient Page" (PDF). Journal of the American Medical Association 294 (20): 2660. American Medical Association. 
  3. ^ Norman/Georgetown spleen
  4. ^ Histology at BU 07701loa
  5. ^ Carey, Bjorn. "Horse science: What makes a Derby winner - Spleen acts as 'natural blood doper,' scientist says", MSNBC.com, Microsoft, May 5, 2006. Retrieved on 2006-05-09. 

[edit] External links

Look up spleen in Wiktionary, the free dictionary.
v • d • e
Immune system: Lymphatic system (Lymph, Lymphocytes)
Primary
Secondary: Spleen (blood)
Secondary: Lymph nodes (extracellular fluid)
Secondary: MALT (mucosa)