Besides beta cells, PI are composed of alpha, delta, epsilon, and
PP cells secreting glucagon, somatostatin (SST), ghrelin, and pancreatic polypeptide (PPY), respectively [4].
Islets have a central core of insulin-secreting (Beta) cells and a surrounding mantle of a, d and
PP cells. The beta cells are differnt in pattern amongst species but they are always clumped together with an adjacent mix of non-beta cells.