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    anatomy and physiology of liver

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    1 : ANATOMY & PHYSIOLOGY OF LIVER A. SUBRAHMANYAM 9th semester
    2 : ANATOMY OF LIVER Liver is a large, solid, wedge shaped gland which occupies whole of right hypochondrium, the greater part of the epigastrium and part of the left hypochondrium upto the left lateral plane. It is the largest gland of the body and contributes about 2% of the total body weight. Weighs 1600gm in male and 1300gm in female
    3 : It has five surfaces: Anterior Posterior Superior Inferior and Right It is divided into right and left lobe by falciform ligament anteriorly and superiorly, by the fissure of ligamentum teres inferiorly and by the fissure for ligamentum venosum posterioly. Right lobe is much larger than the left lobe and forms five sixth of the liver , and also presents the caudate and quadrate lobe.
    4 : Porta hepatis is a deep , transverse fissure situated on the inferior surface of the right lobe. Portal vein , the hepatic artery and the hepatic plexus of nerves enter the liver through the porta hepatis while right and left hepatic ducts and few lymphatics leave it.
    5 : Hepatic segments. On the basis of intrahepatic distribution of hepatic artery, portal vein and biliary ducts, liver is divided into right and left hemilivers. Further divided into a total of eight segments. Each segments have their own hepatic artery branch and biliary tree.
    6 :
    7 : Blood supply 80% of blood supply is derived from portal vein. 20% is derived from hepatic artery. Before entering the liver both hepatic artery and portal vein divide into right and left branches. Within the liver they redivide into segmental vessels, which further divide to form interlobular vessels which run in portal canals.
    8 : Lymphatic drainage Superficial lymphatics terminate in: Caval Hepatic Paracardial and Coeliac lymph node. Deep lymphatics terminate in: Supra diaphragmatic and Hepatic lymph node. Nerve supply Liver receives its nerve supply from hepatic plexus which contains both sympathetic and parasympathetic or vagal plexus.
    9 : Histology of liver
    10 : Each segment is made up of multiple smaller units known as hepatic lobule. Each lobule appears to be made up of cords of liver cells that are separated by sinusoids. Along the periphery of each lobule there are portal canals. Each canal contains: a) A branch of the portal vein b) A branch of the hepatic artery c) An interlobular bile duct. These three structures collectively form a portal triad.
    11 : Blood from the branch of the portal vein, and from the branch of the hepatic artery, enters the sinusoids at the periphery of the lobule and passes towards its centre. Here the sinusoids open into a central vein that occupies the centre of the lobule . In contrast the flow of bile is in opposite direction along the biliary canaliculi into terminal bile ductules and subsequently into interlobular bile ducts located in the portal tracts.
    12 : The sinusoids are lined by an endothelium in which there are numerous pores. Interspersed amongst the endothelial cells there are hepatic macrophages i.e kupffer cells.
    13 : The surface of the liver cell is separated from the endothelial lining of the sinusoid by a narrow perisinusoidal space of disse, which contains stellate cells. These stellate cells play a role in the storage and metabolism of vitamin A and are transformed into collagen producing myofibroblasts when there is inflammation of the liver.
    14 : Liver physiology Liver performs many different functions which can be summarized as: 1. Synthesis of bile salts These are the salts of bile acids. Primary bile acids is cholic and chenodeoxycholic acid. Secondary is deoxycholic and lithocholic acid. These bile acids conjugate with amino acid taurine or glycine and the form salts of Na or K. These bile salts undergo enterohepatic circulation.
    15 : 2. Synthesis of proteins: Albumin Blood coagulation factors I,II,V,VII,IX,X and also fibrinolytic agents. Transport proteins like Ceruloplasmin and Transferrin. Angiotensinogen
    16 : 3. Fat metabolism Oxidation of fatty acids to supply energy for other body functions. Synthesis of large quantities of cholesterol, phospholipids and most lipoproteins. Synthesis of fat from proteins and carbohydrates
    17 : 4. Carbohydrate metabolism Storage of large amounts of glycogen. Conversion of galactose and fructose to glucose. Gluconeogenesis Formation of many chemical compounds from intermediate products of carbohydrate metabolism.
    18 : 5. Vitamin metabolism 25 hydroxylation of vitamin D3 6. Formation of urea 7. Responsible for inactivation of many drugs 8. Detoxification of many toxic substances. 9. Metabolism of ethanol. 10. De-activation of various hormones. 11. Excretion of bile pigments, cholesterol and some metals. 12. Stores iron as ferritin and also vitamins A, D and B12.
    19 : Thank you

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