BIOS 256 AP 4 Exam Elaborations

Week 2: Chapter 24: The Digestive System part two Basic GI Functions • Primary function: movement of nutrient molecules from the external environment to the internal environment. (Absorption of nutrients) Food-Digestion-motility and absorption Pancreas • Gland in the retroperitoneal space behind the stomach • Produces enzymes that digest carbs, proteins, fats, and nucleic acids • Produces the sodium bicarbonate buffer • Empties the contents into duodenum Relationship of the Pancreas to the Liver, Gallbladder, and Duodenum Know: Hepatopancreatic ampulla (ampulla of vater) and Sphincter of Oddi • Sphincter of Oddi regulates the passage of bile and pancreatic juices through the ampulla of vater into the duodenum of the small intestines. Activation of Pancreatic Proteolytic Enzymes Pancreas • Exocrine portion secretes pancreatic juices. o Made up of acini (99% of pancreas) o Pancreatic juice is made up of  Amylase to digest starch  Trypsin, Chymotrypsin, carboxypeptidase, and elastase to digest protein.  Lipase digests triglyceride  Ribonuclease  Deoxyribose o Protein Digesting enzymes secreted in inactive form o NaCO3 buffers acidic gastric juice to allow digestion to begin in small intestines • Endocrine portion secretes hormones like insulin, glucagon o Made up of pancreatic islet cells Liver Split into right and left lobes, separated by the falciform ligament. Right lobe is larger than the left. Histology of the Liver • Hepatocytes o Functional cell of the liver o Produce and secrete bile • Bile canaliculi o Small ducts between hepatocytes that collect bile produced by hepatocytes o Bile canaliculi- bile ductules-bile ducts-right and left hepatic ducts-common hepatic duct-cystic duct=common bile duct • Hepatic sinusoids o Blood capillaries between hepatocytes Right and left hepatic ducts merge to form the common bile duct. Blood Supply of the Liver Oxygenated blood from hepatic artery and Nutrient rich deoxygenated blood from hepatic portal vein go to hepatic sinusoids. Then to central vein. Then hepatic vein. The inferior vena cava. And finally right atrium of the heart Functions of the Liver and Gallbladder • Carbohydrate, lipid, and protein metabolism • Processing of drugs and hormones (detoxifies) • Bilirubin excretion (derived from Heme and metabolized in small intestine by bacteria and eliminated feces. ) • Bile salt synthesis • Storage of vitamins • Phagocytosis of aged RBCs and WBCs and some bacteria • Vitamin D activation Liver and Gallbladder