Duodenum, pancreas, spleen and gall bladder. Illustration of the region of the small intestine where the pancreas (centre) and gall bladder (green, upper left) discharge digestive fluids. The pancreas lies behind the stomach (not shown). Cells in the pancreas (yellow) secrete digestive juices and the hormones insulin and glucagon, which regulate blood sugar levels. The digestive juices collect in a central duct (green) that joins with the common bile duct that brings bile from the gall bladder. These digestive juices are discharged into the duodenum, the beginning of the small intestine that receives food from the stomach. The discharge point is known as the ampulla of Vater (or the hepatopancreatic duct). The spleen is shown at top right. Major blood vessels (arteries, red; and veins, blue) are also shown.