the pancreas and release of insulin

• the pancreas is a small organ lying below the stomach, it has both exocrine and endocrine functions.
• What are the two main secretions of the pancreas?


  Pancreatic juices that contain enzymes whic hare secreted into the small intestine.

  Hormones which are secreted from the islets of langerhans into the blood
• excocrine glands secrete substances into a duct.
• Most cells in the pancreas synthesize and release digestive enzymes. this is the exocrine function of the pancreas. the exocrine cells are small groups surrounding tiny tubules. each group of cells is called an acinus, or acini for plural.
• The acini of the pancreas are grouped into small lobules separated by connective tissue. The cells of the acini secrete the enzymes that they synthesize into the tubule at the centre of the group. The tubules from the acini join together to form intralobular ducts that eventually combine to make up the pancreatic duct. the pancreatic duct carries the fluid containing the enzymes into the first part of the small intestine - the duodenum.
• the fluid from the pancreatic duct contains the following enzymes:

  Pancreatic amylase- a carbohydrase which digests amylose into maltose

  Pancreatic prypsinogen, an inactive protease which will be converted into the active form trypsin when it enters the duodenum

  Lipase- an enzyme which digests lipid molecules.

  
  

  the fluid also contains sodium hydrogencarbonate, this makes the fluid alkaline. This helps to neutralise the contents of the digestive system that have just left the acidic environment of the stomach.
• the islets of langerhans contain the alpha and beta cells which make the endocrine tissue of the pancreas.
• Alpha cells of islets of langerhans secrete glucagon
• Beta cells of islets of langerhans secrete insulin
• when insulin is secreted from the beta cells in the islets of Langerhans, it brings about effects that reduce blood glucose concentration. if the concentration is too high, then it is important that insulin is released from the beta cells. but if the concentration is too low, then secretion needs to stop.