TCM 115 Digestive System Handout (Part 3) PDF

**[TCM 115 -- Basic Anatomy and Physiology]** **[DIGESTIVE (ALIMENTARY) SYSTEM -- HANDOUT (part 3)]** **Pancreas** - Pancreas is a combination of endocrine (ductless) and exocrine (ducted) gland - Endocrine pancreas releases insulin and glucagon -- hormones that regulate levels of bl...

**[TCM 115 -- Basic Anatomy and Physiology]** **[DIGESTIVE (ALIMENTARY) SYSTEM -- HANDOUT (part 3)]** **Pancreas** - Pancreas is a combination of endocrine (ductless) and exocrine (ducted) gland - Endocrine pancreas releases insulin and glucagon -- hormones that regulate levels of blood sugar. - Exocrine pancreas produces pancreatic enzymes and glandular alkaline secretion which is released directly into duodenum. Pancreas is composed of the following parts: a. Head (directly in contact with duodenum) b. Uncinate process c. Neck d. Body e. Tail (extending all the way to the upper left abdominal quadrant) - Pancreas is situated retroperitoneally and it comes into contact with different structures of abdominal cavity. **Drainage of the exocrine pancreas:** There are two ducts that allow pancreatic juice to reach the lumen of duodenum: the main pancreatic duct (duct of Wirsung) and the minor (accessory) duct, which is also known as the duct of Santorini. Main pancreatic duct unites with the common bile duct and they form the hepatopancreatic ampulla. The hepatopancreatic ampulla opens into duodenum at the major duodenal papilla. Major duodenal papilla opens and closes periodically and it is controlled by the sphincter of Odii. Physiology of pancreas ====================== - 99% of the pancreas functions as an exocrine gland -- cells are arranged in clusters called acini. They secrete pancreatic juice - 1% of pancreatic tissue is endocrine pancreas -- cells are arranged in the form of pancreatic islets (of Langerhans) -- secrete glucagon and insulin - Pancreas secretion is between 1200-1500 ml per day. Water, salts, bicarbonate ions and enzymes are included in pancreatic juice. pH value is between 7.1-8.2 so that it buffers acidic content coming from stomach. Alkalinity of pancreatic juice stops the action of pepsin. - Enzymes of the pancreatic juice: - - - - - Inactivated forms of enzymes are produced by pancreas such as trypsinogen in order to prevent self-digestion. These enzymes are activated only when released into GI tract. Enterokinase activates trypsinogen and converts it into trypsin. **Regulation of pancreatic secretion** - Regulated by neuronal and hormonal mechanisms - Cephalic and gastric phase (see Handout \#2 -- Stimulation of gastric secretion by vagus nerve). Vagus also stimulates the pancreas to secrete pancreatic juice. - When chyme that is rich in fats and proteins enters duodenum, the duodenum releases secretin and CCK. Secretin increases production of pancreatic juice rich in bicarbonates, while CCK stimulates release of pancreatic enzymes **Liver** Liver is the largest abdominal organ, located in upper right and upper left abdominal quadrants. Liver produces and secretes bile into duodenum (bile is essential for absorption of lipids). Liver is a major chemical lab of the body. aThe portal venous system collects the venous blood from digestive tube and feeds it into the liver. (See the Vena porta system at the end of this handout). - Liver is mostly intraperitoneal organ (covered with visceral peritoneum) Anatomically, this large organ exhibits two different surfaces, the diaphragmatic (convex, smooth, conforming to the diaphragmatic curvature) and visceral (inferior surface). They are sharply demarcated by the anterior border. The diaphragmatic surface is almost entirely covered with visceral peritoneum. It is divided into left and right lobes by the falciform ligament. The falciform ligament suspends the large and heavy liver to the underside of the diaphragm. Visceral hepatic surface also shows partition of liver's tissue into lobes. There are two main lobes: left and right, but on the visceral surface, it appears that liver possesses two additional, smaller lobes: the caudal and the quadrate lobe. Both caudate and quadrate lobes functionally and structurally belong to the left lobe. **Hepatic blood supply:** Portal vein brings close to 70% of blood delivered into liver (this is liver's functional blood supply). Remaining 30% is brought by the hepatic artery which provides structural supply to liver. Hepatic veins drain the blood into. **Organization of liver tissue** Functional cells that form liver tissue are called hepatocytes. Their principal arrangement is into hexagonally shaped hepatic lobules. Each lobulus receives blood from hepatic artery's and portal vein's branches. Blood passes through the sinusoid capillaries of the lobule and runs towards the center where it is collected by the central vein of a lobule. Peripherally, around the lobule, one will find biliary canaliculi, that together with arterial and venous branches compose the interlobar triad. Biliary canaliculi merge and form larger biliary ducts, which ultimately give rise to left and right hepatic ducts.