Chapter 12 - Endocrine pancreas

Abstract

The pancreas is a soft, slender organ located in the upper abdomen directly behind the stomach and next to the small intestine. It is primarily an exocrine gland secreting a variety of digestive enzymes and pancreatic juice. It is also a very important endocrine gland secreting hormones, insulin and glucagon, which are essential in regulating blood glucose concentrations. The pancreatic exocrine function is carried out by acinar cells. Pancreatic juice rich in digestive enzymes is transported into the small intestine by the pancreatic duct. This chapter describes the location and the structure of the pancreas, and the histology and function of the pancreatic islets (islets of Langerhans). It differentiates the cells that synthesize insulin from other cells in the islets of Langerhans. Name the peptide that is released along with insulin. The steps involved in the synthesis of insulin are described, and the mechanism is explained by which insulin is released, including the stimuli for its release. The mechanism of action of insulin at its target cell is also explained. The cells that synthesize and release glucagon are named, and the trigger for the release of glucagon is explained. The chapter compares and contrasts the functions of insulin and glucagon in maintaining normal blood glucose concentration. Finally, it defines absorptive and postabsorptive (fasting) states, and explains the roles of glucagon and insulin in these states.