Hepatobilliary System: Source of Bile, composition and its functions
- 1. BILE SOURCE , COMPOSITION & FUNCTION Presented by – SNEHASIS ADHIKARY BACHELOR OF SCIENCE IN PHYSICIAN ASSISTANT DEPARTMENT OF ALLIED HEALTH SCIENCE
- 2. INTRODUCTION OF BILE Bile is secreated from the liver. Human liver secreates about 0.5 to 1 liter of bile per day. Secreation of bile is important for digestion and absorption of fat. Bile stored in gallbladder. It released from gallbladder into the intestine whenever it is required.
- 3. FUNCTIONAL ANATOMY Bile is formed in the liver and is excreadted through the bile ductules. The bile ductules along with the branches of portal vein and hepatic artery from the portal triad. The portal triad opens into the hepatic sinusoids. The sinusoidds are surrounded by hepatocytes. The hepatocytes are in intimate contact with the sinusoidal blood. The bile canaliculi start at the space between two hepatocytes, which opens into bile ductules. Bile ductules then form the bile duct which leads to hepatic duct. The right and left hepatic ducts join to form common hepatic duct. The cystic duct from gallblader combines with hepatic duct to form common bile duct. Common ble duct combines with pancreatic duct and opens to second part of duodenum through sphincter of Oddi.
- 5. There are two types of bile based on their location : 1. Hepatic Bile : situated inside of the liver 2. Gallbladder Bile : situated inside of the gallbladder
- 6. COMPOSITION OF BILE Bile is a greenish yellow fluid formed in the liver and stored in gallbladder. It is compossed of water (97.6%) and solids(2.4%) that mainly include some organic and inorganic substances.
- 7. BILE ACIDS & BILE SALTS BILE ACIDS 1. The primary bile acids are cholic acid and chenodeoxycholic acid. The primary bile acids are formed in the hepatocytes from cholesterol. 2. Secondary bile acids are deoxycholic acid and lithocholic acid. The secondary bile acids are produced in the intestine where intestinal bacteria convert primary bile acidds into secondary bile acids. BILE SALTS Bile ssalts are Na+ and K+ salts of bile acid. Bile acids are conjugated with taurine or glycine to form taurocholic acid or glycocholic acid. These acids then combine with sodium and potassium salts to form Na+ - taurocholate, Na+ - glycocholate, K+ - taurocholate and K+ - glycocholate respectively.
- 9. FUNCTION OF BILE SALT Absorption of Fat : This depends on formation of micelles by bile salts in the intestine. Lipids are transported in micelles from the lumen to membrane of intestinal mucosal epithelial cells where micelle dissociates and lipids are absorbed. Emulsification of Fat : Bile salts are surface tension reducing agents. Along with phopholipids and monoglycerides, they cause emulsification of fat, which is essential for digestion and absorption of fat.
- 10. FUNCTION OF BILE SALT Source of bile acid : Bile salts are converted to bile acids in the intestine, which are then absorbed into portal blood. Bile secretion : Bile salts are important choleretics. They are constituent of bile and also they stimulate bile secretion. Activation of pancreatic enzymes : Bile salts activate pancreatic lipase.
- 11. FUNCTION OF BILE SALT Absorption of fat-soluble vitamins : Bile salts facilitate absoption of fat soluble vitamins (vitamins A,D,E & K). Prevention of gallstone formation : Bile ssalts along with lecithin solubilize cholesterol. Thus , they prevent formation of stones in the gallbladder. Prevention of bacterial growth : Bile maintains pH of intestinal content and prevent overgrowth of bacteria in intestine. Stool color : Bile salts add natural brownish color to the stool.
- 12. BILE PIGMENT Bile pigments are the excretory products in bile. Biliverdin and bilirubin are the two bile pigments and bilirubin is the major bile pigment in human beings. Bile pigments are formed during breakdown of hemoglobin, which is released from the destroyed RBCs in the reticuloendothelial system.
- 14. FUNCTION OF BILE 1. Bile helps in absorption of lipid from intestine by forming micelles. 2. Bile salts in bile are important choleretics(increase bile secretion). 3. Bile promotes absorption of fat soluble vitamins (A,D,E,K). 4. Bile ssalts activate pancreatic lipase. 5. Bile pigments (bilirubin & biliverdin) are responsible for greenish-yellow coloration of gallbladder that helps to identify the organ especially in small animals.
- 15. REFERENCE 1. Essentials of MEDICAL PHYSIOLOGY by K Sembulingam & Prema Sembulingam (Sixth Edition) 2. Comprehensive Textbook of MEDICAL PHYSIOLOGY by G K Pal , Pravati Pal & Nivedita Nanda (First Edition)
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