The upper middle region of the abdomen, between the umbilical and hypochondriac regions.
Pancreatic tissue is present in all vertebrate species, but its precise form and arrangement varies widely. There may be up to three separate pancreases, two of which arise from ventral buds, and the other dorsally. In most species (including humans), these fuse in the adult, but there are several exceptions.
Even when a single pancreas is present, two or three pancreatic ducts may persist, each draining separately into the duodenum (or an equivalent part of the foregut). Birds, for example, typically have three such ducts.
In teleosts, and a few other species (such as rabbits), there is no discrete pancreas at all, with pancreatic tissue being distributed diffusely across the mesentery and even within other nearby organs, such as the liver or spleen.
The tail is the left end of the pancreas. It lies in contact with the spleen.
The superior pancreaticoduodenal artery from the gastroduodenal artery and the inferior pancreaticoduodenal artery from the superior mesenteric artery run in the groove between the pancreas and the duodenum and supply the head of pancreas.
The pancreatic branches of the splenic artery also supply the neck, body, and tail of the pancreas. The body and neck of the pancreas drain into the splenic vein; the head drains into the superior mesenteric and portal veins. Lymph is drained via the splenic, celiac, and superior mesenteric lymph nodes.