Question

explain the function of pancreatic and biliary secretion in digestion

Answer 1

When food enters the duodenum,the gall bladder contracts and the sphincter of Oddi relaxes.Relaxation of the sphincter of Oddi allows the bile to enter the intestine.This response is mediated by secretion of the hormone cholecystokinin-pancreozymin from the intestinal wall.Bile is composed of water and electrolytes along with significant amounts o lecithin,fattyacids,cholesterol,bilirubin and bile salts.The bile salts ,together with cholesterol,assist in emulsification of fats in the distal ileum.They are then reabsorbed into the portal blood for return to the liver,after which they are once again excreted into the bile.This pathway from hepatocytes to bile to intestine and back to the hpatocytes is called the enterohepatic circulation.Because of the enterohepatic circultion,only a small fraction of the bile salts that enter the intestine are excreted in the faeces.

The endocrine and exocrine functions of the pancreas are interrelated.The major exocrine function is tio facilitate digestion through secretion of enzymes into the proximal duodenum.Secretin and CCK-PZ are hormones from the gastrointestinal tract that aid in the digestion of food substances by controllingthe secretions of the pancreas.Neural factors also influence pancreatic enzyme secretion.Considerable dysfunction of the pancreas may occur before enzyme secretion decreases and protein and fat digestion becomes impaired.Pancreatic enzyme secretion is normally 1500 to 2500ml/day.