Tags: Anatomical Structure.
The duodenal cap or duodenal ampulla is the very first part of the duodenum which is slightly dilated.It is the part which is intraperitoneal and is about 2 cm long.It is mobile and has a mesentery. It is also smooth walled.It is the most common location of duodenal ulcers as it is where the acidic chyme meets the duodenal mucosa before mixing with the alkaline secretions of the duodenum.