The duodenum is the first and shortest section of the small intestine in most of higher vertebrates. It is a part of the gastrointestinal (GI) tract, connected with the pyloric sphincter of the stomach on its superior end and the jejunum of the small intestine on its inferior end. Duodenum can receive partially digested food (chyme) from the stomach and plays a critical role in the chemical digestion of chyme in preparation for absorption in the small intestine. Many chemical secretions from the pancreas, liver and gallbladder mix with the chyme in the duodenum to facilitate chemical digestion. The duodenum is the principal site for iron absorption in mammals. It is the most common site of inflammatory lesions of the gastro-intestinal tract that is also known as duodenitis mainly caused by bacterium Helicobacter pylori infection. Other diseases that may be associated with duodenitis include celiac disease, Crohn disease and Whipple disease. Duodenal cancer also can occur in duodenum. Currently, various target molecules expressed on duodenum tissue are used to some clinical diagnosis or targeted therapies.
