The duodenum is an organ located just below the stomach and its functions include the continuation of the digestion process and the regulation of gastric emptying. The organ is a part of the small intestine, and it is found in most vertebrates, such as mammals, birds and reptiles.
Most of the chemical digestion of food takes place in the duodenum. Partially digested food from the stomach called "chyme" is emptied into the duodenum via the pylorus, which is a small valve that controls the amount of chyme that enters the duodenum.
The intestinal wall along the duodenum is lined with crypts from which the the enzymes and intestinal juices are secreted to help break down the chyme further. Bile from the liver and gall bladder, as well as pancreatic juice, also seep into the duodenum and these substances help in the digestion process.
The duodenum is the shortest part of the small intestines an it precedes the jejunum and the ileum. This c-shaped intestinal organ is divided into several sections: the first part or superior part, the second part or the descending part and the third part, also called the horizontal or inferior part.
Hunger signals are also triggered by the duodenum by releasing the hormones secretin and cholecystokinin via the duodenal epithelium. These two hormones stimulate the release of bile and pancreatic juices whenever excess stomach and fatty acids are present within the small intestines.