- Pancreas (Digestive System)
The pancreas lies in the J-shaped loop between the stomach and the small intestine. It is elongated, about 15 cm long (6 inches), and weighs about 80 grams (3 ounces). Although it contains both exocrine and endocrine cells, it is primarily an exocrine organ.
- Exocrine cells produce large quantities of an alkaline enzyme-rich fluid that is secreted into the digestive tract in answer to a hormonal response from the duodenum. Among its components is the buffer sodium bicarbonate which regulates the pH level of the chyme. Another hormone, CCK (cholecystokinin), controls the production and secretion of pancreatic enzymes necessary for the digestion of lipids, proteins, sugars, and starches.
- Endocrine cells form clusters known as pancreatic islets (islets of Langerhans), which accounts for only about 1% of all pancreatic cells. Each islet contains several cell types with two of the most important being alpha cells (which produce the hormone glucagon) and beta cells (which secrete insulin). Glucagon raises blood glucose. Insulin lowers blood glucose and is vital for the absorption of glucose for all cells. A pancreatic polypeptide (somatostatin) is also released by delta cells of the islets of Langerhans to inhibit the release of glucagon and insulin.