Gastrointestinal Flashcards
What are the functions of the liver?
1) storage (carbohydrates, triglycerides, all fat soluble vitamins, some water soluble vitamins, iron, copper)
2) Synthetic (bile, clotting factors, albumin)
3) Metabolic (carbonhydrates, fat, proteins, bilirubin, drugs and toxins)
4) endocrine (angiotensinogen production, IGF-1, T4 to T3 conversion)
5) Immune (Kupffer cells phagocytosis in hepatic reticuloendothelial system).
6) Acid- base balance (organic acid metabolism, CO2 production, ammonium, plasma protein produciton.
Describe the livers role in carbohydrate metabolism
Several processes of carbohydrate metabolism occur in the liver in order to maintain a normal plasma glucose concentration.
1) glycolysis- glycolysis, like all cells in the body, the hepatic cells produce energy via transforming glucose into pyruvate.
2) glycogenesis- after a meal, blood glucose concentration rises and insulin is released from the pancreas. Insulin stimulates the liver to polymerise excess glucose into its storage form- glycogen.
3) glycogenolysis- when blood glucose drops, insulin secretion decreases and the pancreas releases glucagon. The liver responds to glucagon by breaking down its glycogen store to release glucose.
4) gluconeogenesis- glucagon also stimulates the liver to synthesis glucose from non- carbohydrate precursors (amino acids, lactate and glycerol)
How does the liver effect fat metabolism?
1) lipid breakdown- hepatocyte mitochondria break down free fatty acids via Beta oxidation.
2) lipid synthesis- the liver synthesises triglyceride and cholesterol. Triglyceride is synthesised from excess glucose. Cholesterol is used as a structual component of cell membranes and a precursor module for hormones and bile salts.
3) lipid processing- Apolipoproteins are synthesises in the liver, these are involved in the packaging of cholesterol and triglyceride as LDL, VLDL and HDL.
