Pancreas : Pancreas The pancreas is both an endocrine and an exocrine gland. It is a wedge-shaped elongated gland which lies in the abdominal cavity.
Structurally the pancreas can be divided into three regions: the head, which lies over the vena cava in the C-shaped curve of the duodenum; the body, which lies behind the duodenum; and the tail, which is situated under the spleen.
The pancreas is composed of two types of cell, exocrine and endocrine cells.
Slide 3: Exocrine Function
Pyramidal acinar cells are exocrine cells that compose the bulk of pancreatic tissue. Groups of acinar cells form an acinus, and groups of acini form grapelike lobules. The acini secrete the digestive enzymes of the pancreatic juice.
Pancreatic enzymes - these enzymes are released from the pancreatic acinar cells and are involved in the digestion of foodstuffs.
There are three main types of enzyme present in pancreatic juice:
Amylases, which break down carbohydrates into glucose and maltose.
Lipases, which are important in the early stages of fat breakdown.
Proteases, including trypsinogen, the precursor of proteolytic trypsin.
Slide 4: Endocrine Function
Endocrine cells, or the islets of Langerhan, make up 1% of the pancreatic cells. They are most numerous in the tail region of the pancreas. They consist of clusters of cells surrounded by pancreatic acini. The major endocrine cells of the pancreas are alpha, beta and delta cells, which secrete glucagons, insulin and somatostatin, respectively.
When the blood sugar level falls below normal levels, the alpha cells are stimulated to secrete glucagon, which accelerates the conversion of glycogen to glucose in the liver. When the blood sugar level is above normal, the beta cells secrete insulin, which promotes both the metabolism of glucose by tissue cells and the conversion of glucose to glycogen, which is then stored in the liver.
Insulin : Insulin Beta cells have channels in their plasma membrane that serve as glucose detectors. Beta cells secrete insulin in response to a rising level of circulating glucose ("blood sugar").
The actions of insulin on the global human metabolism level include:
Control of cellular intake of certain substances, most prominently glucose in muscle and adipose tissue (about ⅔ of body cells).
Increase of DNA replication and protein synthesis via control of amino acid uptake.
Modification of the activity of numerous enzymes.
Slide 6: The actions of insulin on cells include:
Increased glycogen synthesis
Increased fatty acid synthesis
Increased esterification of fatty acids
Increased amino acid uptake
Increased potassium uptake
Arterial muscle tone
Increase in the secretion of HCl by Parietal cells in the stomach
Role of the Insulin : Role of the Insulin