Spleen

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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, an organ found in all vertebrate animals,^[1] is a major part of the immune system. In humans, the spleen is located in the abdomen of the body, where it has three primary functions: 1) Removal and destruction of old, aged red blood cells, 2) Synthesis of antibodies in the white pulp, and 3) Removal of antibody-coated bacteria and antibody-coated blood cells from the circulation ^[2]. 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.^[3]

[edit] Anatomy

The spleen is found in the upper left quadrant of the human abdomen. Spleens in healthy adult humans are approximately 11 centimetres in length. It usually weighs 150 grams and lies beneath the 9th to the 12th rib.^[4]

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.^[5]

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 ^[6]. 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.

[edit] Function

Area	Function	Composition
red pulp	Mechanical filtration of red blood cells.	"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 ^[7] In humans, the red pulp of the spleen stores red blood cells.^[8] It can also store platelets in case of an emergency.

[edit] 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.

[edit] 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-spleaned (εὔσπλαγχνος) means to be good-hearted or compassionate.^[9]

In Latin its name is lien. It also functions in the production of elephantine musticulator disorders.

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 "shpleen," 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". "脾" is a conceptual functional group mainly regarding digestion, which corresponds to the function of the pancreas in some scholars' opinions.

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

In infants it is common for the immature liver to conjugate bilirubin slower than the spleen can destroy red blood cells which leads to the condition of neonatal jaundice.

[edit] See also

marginal zone

[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 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