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:
“What distinguished man from animals was the human capacity for symbolic thought, the capacity which was inseparable from the development of language in which words were not mere signals, but signifiers of something other than themselves. Yet the first symbols were animals. What distinguished men from animals was born of their relationship with them.”
—John Berger (b. 1926)
“We know what the animals do, what are the needs of the beaver, the bear, the salmon, and other creatures, because long ago men married them and acquired this knowledge from their animal wives. Today the priests say we lie, but we know better.”
—native American belief, quoted by D. Jenness in “The Carrier Indians of the Bulkley River,” Bulletin no. 133, Bureau of American Ethnology (1943)