Illustration of the duodenum (here, Cshaped and coloured red), with accompanying pancreas (yellow) and gall bladder (green). A main artery and vein are seen passing through this region. The duodenum is the first part of the small intestine, extend ing after the stomach to the jejunum. As a major secretory region of the gut, serving to further break down food that has entered the stomach, the duodenum also receives secretory products from other organs. Enzymes from the pancreas and bile from the gall bladder (including liver enzymes) pass into ducts which feed into the duodenum through the ampulla of Vater, a small opening. The duodenum is also a site of peptic ulcers.