Physiology and Pharmacology of the Liver Flashcards
What are the major metabolic functions of the liver?
Carbohydrate metabolism
Fat metabolism and synthesis of lipoproteins etc.
Protein metabolism
What gets degraded in the liver?
Insulin
Steroid hormones
Glucagon
ADH
What is stored in the liver?
Vit A and Vit B12
Copper and iron
Glycogen
How does the liver protect the body?
Liver phagocytes digest/destroy any cellular debris and invading bacteria
Liver detoxifies both endogenous and exogenous substances
Describe the secretion of bile
Bile is stored and concentrated in the gallbladder between meals.
During a meal, chyme in the duodenum stimulates smooth muscle to contract (CCK and vagal signals) - this allows bile to enter the duodenum and participate in the digestion and absorption of fats
What does bile contain?
Secretion of hepatocytes Secretion of bile duct cells Water and electrolytes Lipids and phospholipids Cholesterol IgA Bilirubin
Describe the role of drugs in the biliary system
Overall limited, but ursodeoxycholic acid may be suitable for an unimpaired gallbladder with small/medium stones and in severe biliary colic morphine/buprenorphine may be used
Describe the use of bile acid salt resins
Bile acid salt resins (colesevelam) bind to bile acids to prevent their reabsorption. Lowers plasma cholesterol indirectly
Describe the phases of drug metabolism in the liver
Phase I - involves oxidation, reduction and hydrolysis to make the drug more polar and adding a chemically reactive group to permit conjugation
Phase II - involves conjugation (endogenous compound added to drug to increase polarity)
What mediates the oxidative reactions in phase I?
Haem proteins found in the endoplasmic reticulum of hepatocytes
What is hepatic encephalopathy?
Ammonia not being toxified to urea, causing blood ammonia levels to rise resulting in a coma
How is hepatic encephalopathy treated?
Lactulose - converts ammonia to ammonium
Antibiotics (neomycin) - suppresses colonic flora to inhibit ammonia generation
