The first part of the small intestine. At the junction of the stomach and the duodenum the alimentary canal is inflected. The duodenum first goes anteriorly for a short distance, turns dorsally, and eventually caudally, thus it is a U-shaped structure with two horizontal sections (a ventral and a dorsal one).

http://upload.wikimedia.org/wikipedia/commons/b/b3/Tractus_intestinalis_duodenum.svg

The fixed portion of the small intestine deeply lodged in the posterior wall of the abdomen and extending from the pylorus to the beginning of the jejunum. [Dorian_AF, Elsevier's_encyclopaedic_dictionary_of_medicine, Part_B:_Anatomy_(1988)_Amsterdam_etc.:_Elsevier][VHOG]

uberon

upper intestine, proximal intestine

duodenal

UBERON:0002114

http://purl.obolibrary.org/obo/uberon.owl, http://purl.obolibrary.org/obo/cl.owl

http://purl.obolibrary.org/obo/NCBITaxon_7955

In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine may be used instead of duodenum., In humans, the duodenum is a hollow jointed tube about 10-15 inches (25-38 centimetres) long connecting the stomach to the jejunum. It begins with the duodenal bulb and ends at the ligament of Treitz.

• pancreatic epithelial bud

• pyloric sphincter

• duodenal mucosa