Unit Thirteen: Metabolism and Temperature Regulation

1. Unit Thirteen: Metabolism and Temperature Regulation Chapter 70: The Liver as an Organ Guyton and Hall, Textbook of Medical Physiology, 12th edition

2. Basic Properties • Physiologic Anatomy of the Liver • Largest organ of the body, contributes about 2% of the • total body weight • Functional unit is the liver lobule; liver contains • 50,000-100,000 individual lobules

3. Basic Properties • Physiologic Anatomy of the Liver Fig. 70.1 Basic structure of a liver lobule

4. Basic Properties • Hepatic Vascular and Lymph Systems • Blood flows through the liver from the portal vein • and hepatic artery • Liver has high blood flow and little vascular • resistance • Liver functions as a blood reservoir • Liver has high lymph flow

5. Basic Properties • Regulation of Liver Mass-Regeneration • The liver can restore itself after significant hepatic • tissue loss • Control mechanisms are largely unknown but may • be regulated by hepatocyte growth factor (HGF) • Once the liver has returned to its normal size, • growth is inhibited, possibly by cytokines • (i.e. transformng growth factor-beta)

6. Basic Properties • Hepatic Macrophage System Serves a Blood • Cleansing Function • Kupffer cells- large phagocytic macrophages that • line the hepatic venous sinuses • Removes approximately 99% of the bacteria • entering the portal blood from the intestinal • tract

7. Basic Properties • Metabolic Functions of the Liver • Carbohydrate metabolism • 1) storage of large amounts of glycogen • 2) conversion of galactose and fructose to glucose • 3) gluconeogenesis • 4) formation of many chemical compounds from • intermediate products of cbh metabolism • 5) important for maintaining a normal blood • glucose concentration

8. Basic Properties • Metabolic Functions of the Liver • Fat metabolism • 1) oxidation of fatty acids to supply energy • for other body functions • 2) synthesis of large quantities of cholesterol, • phopholipids, and most lipoproteins • 3) synthesis of fat from proteins and cbhs

9. Basic Properties • Metabolic Functions of the Liver • c. Protein metabolism • 1) deamination of amino acids • 2) formation of urea for removal of ammonia • from the body fluids • 3) formation of plasma proteins • 4) Interconversions of the various amino acids • and synthesis of other compounds from • amino acids

10. Basic Properties • Metabolic Functions of the Liver • d. Other metabolic functions • 1) storage site for vitamins • 2) stores iron as ferritin • 3) forms the blood substances used in coagulation • 4) removes or excretes drugs, hormones, and • other substances