Ileum

The ileum is the final section of the small intestine. It follows the duodenum and jejunum, and is separated from the cecum by the ileocecal valve (ICV). In humans, the ileum is about 2-4 m long. It is neutral or slightly alkaline with a pH between 7 and 8. It absorves any remaining nutrients from the breakdown of protein.

The main function of the ileum is to absorb vitamin B12 and 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 villi on its surface. In turn, the epithelial cells which line these villi possess even larger numbers of microvilli. Therefore the ileum has an extremely large surface area both for the attachment of enzyme molecules and for the absorption of products of digestion.