Peyer's patches, named in honor of Hans Conrad Peyer, a 17th century anatomist, are an important part of the gastrointestinal immune system. In function and rough appearance, they have much in common with lymph nodes, although they are defined as follicles rather than nodes. They most commonly appear as thickened patches of lymphatic tissue in the mucous membrane of the lowest portion of the small intestine. They harbor a heavy concentration of white blood cells in order to combat harmful bacteria in the intestinal tract.
Peyer's patches were first described in a 1677 publication by Johann Conrad Peyer. Interestingly, Peyer was practicing as a medical student and apprentice under famed cardiologist Raymon Vieussens when he made his discovery. They appear in the medical literature sporadically as sites of ulceration or disease until the early 20th century, when the role of the lymphatic system as part of the immune system began to be emphasized.
Appearance and Location
Peyer's patches appear as a thickening of the intestinal wall about 1 centimeter in diameter. The patches are composed of fibrous lymphatic tissue and are thickly clustered near the transition between the small intestine and the large intestine. Most healthy adults have between 30 and 40 patches, although they grow smaller and may even vanish with age. Peyer's patches are immediately discernible due to the lack of intestinal villi on their surfaces.
Like the lymph nodes, Peyer's patches are collections of lymphatic follicles which produce lymph, a clear liquid containing a high concentration of white blood cells. They thus aid in the production of antibodies and help keep the gastrointestinal system free of harmful pathogens. This is especially important in the lower reaches of the small intestine, which is exposed to a wide variety of potentially harmful bacteria from both the stomach and the large intestine.
Common Diseases and Disorders
Peyer's patches, like other components of the lymphatic system, can become inflamed or ulcerated when the tissue surrounding them becomes inflamed, rendering them permeable to toxins and foreign bacteria. Ulcerated lymphatic structures can act as a gateway for bacteria into the bloodstream, resulting in the spread of infection to other organs and tissues.
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