Anatomy and physiology of the pancreas
The pancreas secretes many hormones, such as amylin, somatostatin, and pancreatic polypeptide, the function of which is unknown. The main purpose is to discuss the physiological roles of insulin and glucagon and the pathophysiology of these diseases.
In addition to its digestive function, the pancreas also secretes two important hormones, insulin and glucagon, which determine the regulation of glucose, lipid, and protein metabolism. Although the pancreas secretes many other hormones, such as amylin, somatostatin, and pancreatic polypeptide, their function is unknown. The main aim is to discuss the physiological roles of insulin and glucagon and the pathophysiology of diseases, especially diabetes, due to abnormalities in the secretion or action of these hormones.
The pancreas is made up of two main types of tissues, as shown: (1) exocrine pancreas, which secretes digestive juices into the duodenum, and (2) Langerhans diuresis, which secretes insulin and glucagon directly into the bloodstream.
Figure. Anatomy and physiology of the islets of Langerhans
In humans, the pancreas has 1 to 2 million islets of Langerhans. Each islet about 0.3 mm in diameter is located around small capillaries. The cells secrete hormones into these capillaries. Islets contain three major cell types: alpha cells, beta cells, and delta cells that differ in morphology and staining characteristics.
Beta cells, which make up about 60% of the total number of cells in the islets, are located mainly in the middle of each islet and secrete insulin, amylin, a hormone normally secreted with insulin, although its function is unknown. Alpha cells, about 25% of the total, secrete glucagon, and delta cells makeup about 10%, secrete somatostatin. In addition, at least one other cell type, the PP cell, is present in small numbers in the islets of the pancreas and secretes a hormone of unknown function called a pancreatic polypeptide.
The close relationship between these cell types in the islets allows for cell-to-cell communication and direct control of hormone secretion by other hormones. For example, insulin inhibits glucagon secretion, amylin inhibits insulin secretion, and somatostatin inhibits both insulin and glucagon secretion.