Editing Ileum (section)

==Function==
The main function of the ileum is to absorb [[vitamin B12|vitamin B<sub>12</sub>]], [[bile salts]], and whatever products of digestion were not absorbed by the jejunum.  The wall itself is made up of folds, each of which has many tiny finger-like projections known as [[Intestinal villus|villi]] on its surface. In turn, the epithelial cells that line these villi possess even larger numbers of [[microvilli]]. Therefore, the ileum has an extremely large surface area both for the [[adsorption]] (attachment) of [[enzyme]] molecules and for the [[Absorption (chemistry)|absorption]] of products of [[digestion]]. The DNES (diffuse neuroendocrine system) cells of the ileum secrete various hormones ([[gastrin]], [[secretin]], [[cholecystokinin]]) into the blood. Cells in the lining of the ileum secrete the [[protease]] and [[carbohydrase]] enzymes responsible for the final stages of [[protein]] and [[carbohydrate]] digestion into the [[Lumen (anatomy)|lumen]] of the intestine. These enzymes are present in the [[cytoplasm]] of the [[epithelial cells]].

The villi contain large numbers of capillaries that take the amino acids and glucose produced by digestion to the [[hepatic portal vein]] and the liver. [[Lacteals]] are small lymph vessels, and are present in villi. They absorb [[fatty acid]] and [[glycerol]], the products of fat digestion. Layers of circular and longitudinal [[smooth muscle]] enable the [[chyme]] (partly digested food and water) to be pushed along the ileum by waves of muscle contractions called [[peristalsis]]. The remaining chyme is passed to the [[Colon (anatomy)|colon]].