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Encyclopedia > Peyer's patches

Peyer's patches are secondary lymphoid organs, 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 (ileum) in humans; as such, they differentiate the ileum from the duodenum and jejunum in that the number of Peyer's patches increase further down the intestine (ie. terminal ileum contains most Peyer's patches). (16th century - 17th century - 18th century - more centuries) As a means of recording the passage of time, the 17th century was that century which lasted from 1601-1700. ... Johann Conrad Peyer (December 26, 1653 - February 29, 1712) was a Swiss anatomist who was a native of Schaffhausen. ... In biology the small intestine is the part of the gastrointestinal tract (gut) between the stomach and the large intestine and includes the duodenum, jejunum, and ileum. ... In anatomy of the digestive system, the duodenum is a hollow jointed tube connecting the stomach to the jejunum. ... Diagram of the Human Intestine In anatomy of the digestive system, the jejunum is the central of the three divisions of the small intestine and lies between the duodenum and the ileum. ... Grays Fig. ...


Location and appearance

Peyer's patches are observable as elongated thickenings of the intestinal epithelium measuring a few centimeters in length. 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. Lymph nodes are components of the lymphatic system. ... Grays Fig. ...


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. Gut redirects here. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... The mucous membranes (or mucosa) are linings of ectodermic origin, covered in epithelium, that line various body cavities and internal organs. ...


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 gut-associated lymphoid tissue (GALT). An antigen or immunogen is a molecule that stimulates an immune response. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... T cells are a subset of lymphocytes that play a large role in the immune response. ... Overview About 70% of the bodys immune system is found in the digestive tract. ...


Peyer's patches contain specialized cells called 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. M cells (or Microfold cells) are cells found in the follicle-associated epithelium of the Peyers patch that have the unique ability to sample antigen from the lumen of the small intestine and deliver it via transcytosis to antigen presenting cells and lymphocytes located in a unique pocket-like... An antigen presenting cell (APC) is a cell that displays foreign antigen complexed with MHC on its surface. ... The abbreviation B comes from bursa of Fabricius that is an organ in birds in which avian B cells mature. ... An antigen or immunogen is a molecule that stimulates an immune response. ... In human anatomy, the thoracic duct is an important part of the lymphatic system — it is the largest lymphatic vessel in the body. ...


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. Bodybuilder Markus Rühl has marked hypertrophy of skeletal muscle. ... An intussusception is a situation in which a part of the intestine has prolapsed into another section of intestine, similar to the way in which the parts of a collapsible telescope slide into one another. ...


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


 
 

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