In Animals
Pancreatic tissue is present in all vertebrate species, but its precise form and arrangement vary 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 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. In a few teleost species, the endocrine tissue has fused to form a distinct gland within the abdominal cavity, but otherwise it is distributed among the exocrine components. The most primitive arrangement, however, appears to be that of lampreys and lungfish, in which pancreatic tissue is found as a number of discrete nodules within the wall of the gut itself, with the exocrine portions being little different from other glandular structures of the intestine.
Read more about this topic: Pancreatic Hormones
Famous quotes containing the word animals:
“There is nothing worse than an idle hour, with no occupation offering. People who have many such hours are simply animals waiting docilely for death. We all come to that state soon or late. It is the curse of senility.”
—H.L. (Henry Lewis)
“who cooked rotten animals lung heart feet tailborscht & tortillas
dreaming of the pure vegetable kingdom,”
—Allen Ginsberg (b. 1926)