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BIOL 2P93 (93)

Liver Histology

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Jenny Janke

Liver and Gall Bladder Histology I. Introduction a. Largest gland in body (~3.5 lbs in adult) b. Composed of 4 incompletely separated lobes; lies in RUQ c. Has thin connective tissue capsule (glisson’s capsule) II. Blood Flow a. Inflow i. Portal Vein—carries venous blood from GI (nutrient rich, O2 poor); supplies 75% afferent blood volume 1. formed from superior & inferior mesenterics, splenic, & gastric veins ii. Hepatic Artery—br. off celiac trunk; carries O2 rich blood; supplies 25% vol. b. Sinusoids—carries mixed blood from portal vein & hepatic artery; blood flows towards center of each lobule & is collected by central veins c. Outflow i. Hepatic vein—carries deoxygenated, filtered blood from liver to heart d. Summary: Hepatic A. & portal vein (interlobar blood vessels) →interlobular branches → sinusoids →central veins →sublobar veins→hepatic veins III. Liver Structure a. Hepatic triad—composed of portal vein, hepatic artery, & bile duct b. Liver allows very close contact between blood & hepatocytes i. Sinusoids have no basement membrane, no pericytes, & fenestrated walls ii. Reticular fibers—collagenous network giving structure to sinusoids iii. Space of Disse—pericapillary space where blood plasma is in direct contact with hepatocytes; site of lymph formation, iv. Lipocytes (Stellate Cells)—lie in place of Disse; store Vitamin A c. Hepatocytes in “plates” 1 cell thick to maximize exposure to blood (2-3 sides exposed) d. Kupffer cells—resident macrophages found in sinusoids; phagocytose bacteria, viruses, & foreign particles IV. Liver Exocrine Function—Bile Secretion a. Bile—formed continuously in liver; composed of bile salts & pigments i. Formation 1. Bile salts—cholesterol derivatives; powerful detergents aiding in emulsification of fats 2. Bile Pigments—derived from degradation of Hgb & excreted via GI * Synthesis & Excretion of Bilirubin: • heme →biliverdin →bilirubin (unconjugated) in macrophages • Bilirubin-albumin complex travels in blood until taken up by hepatocytes • Conjugated bilirubin formed by adding 2 glucuronyl acid groups to it • excreted by kidneys (now H2O soluble & able to be filtered) ii. Exit Path: Liver →R & L hepatic Ducts →(join to form) Common Hepatic Duct →(joins w/) Cystic Duct →(form) Common Bile Duct →Sphincter of Oddi →Ampulla of Vater →Duodenum b. Bile canaliculi—limiting wall composed of apical hepatocyte membranes w/ tight jxns i. Eventually gain walls composed of cuboidal cells w/ basal lamina & microvilli ii. In the liver, bile flows opposite the direction of blood
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