Ileum

The ileum is the final section of the small intestine in humans and other mammals. It is located between the jejunum and the cecum of the large intestine. The ileum is approximately 3 meters (10 feet) long and is a critical part of the digestive system. Its primary function is to absorb the final products of digestion such as vitamins, minerals, and other nutrients. The mucosal surface of the ileum is highly specialized to facilitate nutrient absorption. It contains villi, which are finger-like projections that increase the surface area of the mucosal wall. These villi are covered with tiny microvilli, which further increase the absorptive area. The ileum also contains Peyer’s patches, which are clusters of lymphoid tissue. These patches serve as part of the immune system and help protect the body from invading bacteria and other pathogens. The ileum also contains cells that secrete hormones that regulate digestion, such as cholecystokinin, secretin, and gastrin. In addition to its role in digestion, the ileum is also involved in the absorption of bile salts from the large intestine. Bile salts are necessary for the digestion and absorption of fats.