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Peyer's patch

 
(′pī·ərz ′pach·əz)

(histology) Aggregates of lymph nodules beneath the epithelium of the ileum.


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American Heritage Stedman's Medical Dictionary:

aggregated lymphatic follicles

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pl.n.

Collections of many lymphoid follicles closely packed together, forming oblong elevations on the mucous membrane of the small intestine. Also called aggregate glands, agminate glands, Peyer's patches.


any of numerous subepithelial aggregates of lymphoid tissue found in the intestinal mucosa. The M cells that overlie them transmit bacterial and viral protein antigens, which induce proliferation of the lymphoid cells and the secretory immune response. [After Johann Peyer (1653 — 1712), Swiss anatomist.]

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Saunders Veterinary Dictionary:

Peyer's patches

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Oval, elevated patches of closely packed lymph follicles in mucous and submucous layers of the small intestine. Called also aggregated lymphatic nodules.

  • continuous p. p. — found in the terminal ileum in calves, lambs, piglets. Thought to be a primary site for B-cell generation; involute with age.
Wikipedia on Answers.com:

Peyer's patch

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aggregated lymphoid nodules
[[Image:
A cross section of ILEUM. Peyer's Patch is outlined in red
|250px|]]
Peyer's patches
Latin noduli lymphoidei aggregati
Code TH H3.04.03.0.00020

Peyer's patches (or aggregated lymphoid nodules) are organized lymphoid nodules, named after the 17th-century Swiss anatomist Johann Conrad Peyer. They are aggregations of lymphoid tissue that are usually found in the lowest portion of the small intestine, the ileum, in humans; as such, they differentiate the ileum from the duodenum and jejunum. The duodenum can be identified by Brunner's glands. The Jejunum has neither Brunner's glands nor Peyer's Patches.

Contents

Location and appearance

Peyer's patches are observable as elongated thickenings of the intestinal epithelium measuring a few centimeters in length. About 30 are found in humans. Microscopically, Peyer’s patches appear as oval or round lymphoid follicles (similar to lymph nodes) located in the lamina propria layer of the mucosa and extending into the submucosa of the ileum.

In adults, B lymphocytes are seen to predominate in the follicles' germinal centers. T lymphocytes are found in the zones between follicles.

Function

Because the lumen of the gastrointestinal tract is exposed to the external environment, much of it is populated with potentially pathogenic microorganisms. Peyer's patches thus establish their importance in the immune surveillance of the intestinal lumen and in facilitating the generation of the immune response within the mucosa.

Pathogenic microorganisms and other antigens entering the intestinal tract encounter macrophages, dendritic cells, B-lymphocytes, and T-lymphocytes found in Peyer's patches and other Mucosa Associated Lymphatic Tissue (MALT).

Peyer's patches are covered by a special epithelium that contains specialized cells called microfold cells (M cells) which sample antigen directly from the lumen and deliver it to antigen-presenting cells (located in a unique pocket-like structure on their basolateral side). B-cells and memory cells are stimulated upon encountering antigen in Peyer's patches. These cells then pass to the mesenteric lymph nodes where the immune response is amplified. Activated lymphocytes pass into the blood stream via the thoracic duct and travel to the gut where they carry out their final effector functions.

Pathology

Although important in the immune response, excessive growth of lymphoid tissue in Peyer's patches is pathologic, as hypertrophy of Peyer's patches has been closely associated with idiopathic intussusception.

The hypertrophy of Peyer's patches has also been associated with susceptibility to transmissible spongiform encephalopathies (commonly known as prion diseases).

Salmonella hadar and poliovirus also target this section of the intestine.[1]

References

  1. ^ Pascall, C R; Stearn, E J; Mosley, J G (1980-07-05), "Short Reports", British Medical Journal: 26, PMC 1713722, "Unlike S hadar peritonitis, S typhi peritonitis is due to perforation of Peyer's patches." 

 
 

 

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McGraw-Hill Science & Technology Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
American Heritage Stedman's Medical Dictionary. The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company Read more
 Oxford Dictionary of Biochemistry. Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved.  Read more
Saunders Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia on Answers.com. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Peyer's patch Read more

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