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The ileum (/ ˈ ɪ l i əm /) is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish , the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum. [ 2 ]
The small intestine supports the body's immune system. [20] The presence of gut flora appears to contribute positively to the host's immune system. Peyer's patches, located within the ileum of the small intestine, are an important part of the digestive tract's local immune system. They are part of the lymphatic system, and provide a site for ...
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body.
Intestinal glands are found in the epithelia of the small intestine, namely the duodenum, jejunum, and ileum, and in the large intestine (colon), where they are sometimes called colonic crypts. Intestinal glands of the small intestine contain a base of replicating stem cells , Paneth cells of the innate immune system , and goblet cells , which ...
The histology of the ileocecal valve shows an abrupt change from a villous mucosa pattern of the ileum to a more colonic mucosa. A thickening of the muscularis mucosa, [citation needed] which is the smooth muscle tissue found beneath the mucosal layer of the digestive tract. A thickening of the muscularis externa is also noted. [1]
Unlike the gastric folds in the stomach, they are permanent, and are not obliterated when the intestine is distended.. The spaces between circular folds are smaller than the haustra of the colon, and, in contrast to haustra, circular folds reach around the whole circumference of the intestine.
The gastroileal reflex is stimulated by the presence of food in the stomach and gastric peristalsis. Initiation of the reflex causes peristalsis in the ileum and the opening of the ileocecal valve (which allows the emptying of the ileal contents into the large intestine, or colon). [1]
[3] [4] [5] They constitute an enteric endocrine system as a subset of the endocrine system just as the enteric nervous system is a subset of the nervous system. [6] In a sense they are known to act as chemoreceptors , initiating digestive actions and detecting harmful substances and initiating protective responses.