Overview of the Liver
- 1. The Liver Anatomy Right (middle hepatic vein) Left lobe Right – caudate & quadrate lobes Overall, 8 subdivisions separated by R, middle & L hepatic veins Each section has portal pedicle – individual resection Blood flow: Hepatic/Portal Vein Portal Tracts Sinusoids Branches of Hepatic Veins (finally form 3) IVC Lymph – formed in the perisinusoidal space collected in lymphatics in portal tracts eventually draining into hepatic ducts Acinus – functional liver unit. Made of parenchyma supplied by portal tracts containing portal vein radicles, hepatic arterioles and bile ductules. Sinusoids – a small blood vessel without a continuous endothelium (fenestrated) or basement membrane and has Kupffer cells (phagocytic). They are separated by hepatocytes. Kupffer cells – secrete Ils, TNF, collagenase & lysosomal hydrolases Space of Disse – the subendothelial space between sinusoids and hepatocytes. It contains a basement membrane matrix and stellate cells. Stellate cells – contain desmin. Are activated to myofibroblasts which contract and regulate sinusoidal blood flow. Involved in fibrosis. Blood Supply: Hepatic Artery – from celiac axis (25% blood flow Portal Vein – drains most of GI tract and spleen (75% of blood flow) Enter via porta hepatis Caudate Lobe blood: Receives an independent supply via the portal vein and hepatic artery and drains directly into the IVC
- 2. Liver Function: Protein Metabolism Synthesis & Storage: Makes all circulating proteins (except y-globulins) by receiving amino acids from GI and muscles Plasma – 60-80g/L of protein – mainly in albumin, globulin and fibrinogen Albumin – ½ life of 16-24 days and 10-12g produced per day. Function is to 1. Maintain colloid osmotic pressure and 2. To transport water-insoluble substances e.g. bilirubin, hormones, fatty acids and drugs. Hypoalbuminaemia is seen in chronic liver disease, malnutrition, hypercatabolic states (trauma & sepsis) & where there is excessive loss (nephritic syndrome) Transport/carrier proteins are also formed : transferring, caeruloplasmin Also synthesises fibrinogen, factors 5,7,9,10 and 13, proteins C & S and antithrombin. Stores vitamin A, D & B12, and iron, haemosiderin and copper. Nitrogen Excretion: Amino acids ammonia urea Carbohydrate Metabolism Glucose homeostasis, by storing approx 80g of glycogen. Lipid Metabolism Fats are insoluble in water so transported as lipoproteins.
- 3. Formation of bile and bilirubin metabolism. Hormone and Drug Inactivation – catabolises insulin, glucagon, oestrogens, growth hormone, glucocorticoids and parathyroid hormones Immunological Function – bacteria and other antigens are phagocytosed and degraded by Kupffer cells. Investigations LFTS – serum albumin & bilirubin prothrombin time Liver Biochemistry – serum aspartate and alanine aminotransferases –show hepatocellular damage serum alkaline phosphatise, y-glutamyl transpeptidase - cholestasis total protein