anatomical structures of small intestine, duodenum, ileum and jejunum

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Characteristics and features

Ileum

Synonyms: Intestinum ileum

The ileum is the last of the three parts of the small intestine. The transition from the jejunum to the ileum is not sharply marked, while at the distal end, the ileum opens into the cecum. At the junction between the ileum and the cecum lies the ileocecal valve (ileal ostium), a functional sphincter formed by the circular muscle layers of both the ileum and cecum. It prevents a reflux of the bacteria-rich content from the large intestine into the small intestine.
The ileum makes up about 3/5 of the total length of the small intestine (2.5 to 3.5 meters). Compared to the jejunum, the parallel running circular folds in the mucosa (valves of Kerckring) are less prominent. In contrast it is rich in lymphoid follicles. Similar to the jejunum, the ileum is attached to the posterior wall of the abdomen by the mesentery and therefore lies flexibly in the abdominal cavity

The small intestine is composed of three distinct parts, the last one being the ileum. At the distal end, the ileum is separated from the large intestine, into which it opens, by the ileocecal valve. The ileum itself is very rich in lymphoid follicles and is attached to the abdominal wall by the mesentery. Its vascular supply is provided by the ileal arteries and its innervation via the coeliac and superior mesenteric plexi.
In terms of histology, the mucosa of the ileum consists of simple columnar epithelium comprising of enterocytes and goblet cells. A characteristic histological feature of the ileum are Peyer's patches.
This article will explain both the anatomy and histology of the ileum and provide you with a quick summary at the end to emphasize the important elements that you should remember for your next exam about the small intestine.
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