Transcript The Liver
The Liver WALT • The structure of the liver • The many functions of the liver • The blood supply to and from the liver Hepatocytes- liver cells • Hepatocytes are metabolic superachievers in the body. • They play critical roles in synthesizing molecules that are utilized elsewhere to support homeostasis, in converting molecules of one type to another, and in regulating energy balances. The liver plays a key role in glucose homeostasis: i) glycogenolysis: breakdown of glycogen ii)gluconeogenesis:converting proteins into glucose iii)glycogenesis: converting glucose into glycogen The Liver – is an organ for digestion and homeostasis Blood system associated with the liver Blood Supply to the liver Blood is drained into the liver by 2 vessels: the hepatic artery and the hepatic portal vein Blood is drained away from the liver by the hepatic vein Functions of The Liver The liver has about 500 individual functions. They are grouped as below: 1.Carbohydrate metabolism - action of insulin & glucagon 2.Lipid metabolism - lipids are broken down or transported to storage areas - excess carbohydrates lipid - regulate cholesterol level; atherosclerosis & gall stones 3. Protein metabolism deamination and transamination to synthesize non-essential amino acids 4. Synthesis of plasma proteins, e.g. clotting factors: prothrombin & fibrinogen 5.Production of bile: bilirubin + bile salts + NaCl + HCO36.Storage of vitamins, especially fat soluble vitamins A, D, E, K 7.Storage of minerals e.g. Fe, K, Cu & Zn 8. Formation & breakdown of RBCs foetal liver produces RBCs adult liver breaks down aged RBCs 9. Storage of blood about 1500 cm3 of blood can be stored 10.Hormone breakdown e.g. testosterone, insulin etc 11.Detoxification Kupffer cells ingest foreign materials Hepatocytes convert toxic chemicals into harmless forms 12. Production of heat when body temperature falls triggered by the hypothalamus Making Bile • Bilirubin is a useless and toxic breakdown product of hemoglobin, which also means that it is generated in large quantities. Jaundice • If excessive quantities of bilirubin accumulate in extracellular fluid, a yellow discoloration of the skin, sclera and mucous membranes is observed - this condition is called icterus or jaundice. Protein Metabolism • The human body cannot store proteins • Amino acids like many other digested foods reach the liver via the hepatic portal vein Protein Metabolism • The most critical aspects of protein metabolism that occur in the liver are: • Deamination and transamination of amino acids, followed by conversion of the nonnitrogenous part of those molecules to glucose or lipids. Protein Metabolism 2 • Removal of ammonia from the body by synthesis of urea. • Ammonia is very toxic and if not rapidly and efficiently removed from the circulation, will result in central nervous system disease.