: the last division of the small intestine that constitutes the part between the jejunum and large intestine and in humans forms the last three fifths of the part of the small intestine beyond the end of the duodenum and that is smaller and thinner-walled than the jejunum with fewer circular folds but more numerous Peyer's patches
Illustration of ILEUM
Final and longest segment of the small intestine. It is the site of absorption of vitamin B (seevitamin B complex) and reabsorption of about 90% of conjugated bile salts. It extends about 13 ft (4 m), from the jejunum (middle section of the small intestine) to the ileocecal valve, where it joins the large intestine. Disorders produce vitamin B deficiency and extensive diarrhea (since bile salts in the large intestine interfere with water absorption).