Jejunum

Thursday, January 8, 2009

The Jejunum is the central part of the small intestine between the the duodenum and the ileum. The change from the duodenum to the jejunum is usually defined as the ligament of Treitz. The adult small intestine is about 6 meter long, and the jejunum forms a little less than half of the small intestine. The jejunum and the ileum are suspended by an extensive mesentery giving the bowel great mobility within the abdomen.

The inner surface of the jejunum, its mucous membrane, is covered in projections called villi, which increase the surface area of tissue available to absorb nutrients from the gut contents. The epithelial cells which line these villi possess even larger numbers of microvilli. The transport of nutrients across epithelial cells through the jejunum and ileum includes the passive transport of sugar fructose and the active transport of amino acids, small peptides, vitamins, and most glucose. The villi in the jejunum are much longer than in the duodenum or ileum.