The pancreas has two main functions:
- To supply digestive enzymes for the three main food groups in the form of pancreatic juice
- To supply hormones for the regulation of blood glucose in the form of insulin and glucagon.
The functions of the exocrine and endocrine cells of the pancreas.
The ‘romance of the abdomen; the pancreas lying in the arms of the duodenum’.
There are two different types of glandular tissue exocrine and endocrine.
The pancreas are composed mostly of exocrine cells, with a compound acinar formation which means grape-like and branching, which empty into a duct. These ducts join and unite until they form the main Pancreatic Duct. This empties into the duodenum at the same point as the common bile duct – at the major duodenal papilla.
Acinar units secrete digestive enzymes found in pancreatic juice (e.g. trypsin and chymotrypsin, amylase and lipase)
Embedded between the exocrine units of the pancreas, like so many little islands, lie clusters of endocrine cells called pancreatic islets. Despite their being millions of them, they only make up around 2% of the pancreas. It is mainly Alpha cells (that produce glucagon) and Beta cells (that produce insulin) that make up these islets. (Also; Delta cells produce somatostatin and PP cells produce polypeptides) They are secreting cells but their secretion passes into the blood capillaries instead of into ducts and this is what sets them apart from the exocrine cells.
Endocrine Alpha cells produce glucagon – which opposed the effects of insulin
Endocrine Beta cells produce insulin which increases the uptake of glucose in cells and organs such as the liver.
Insulin operates in a negative feedback loop that prevents blood glucose concentration increasing too far above normal. The pancreas respond to high blood glucose levels by secreting insulin. Insulin promotes the uptake of glucose by all cells of the body, enabling them to catabolise and/or store it. Thus excess glucose is removed from the bloodstream.
Conversely if blood glucose levels fall too far below the set point, the hormone glucagon is secreted by the pancreas which promotes the release of glucose from storage for example in the liver into the blood stream and homeostasis is reestablished.