Functions,Secretion and Regulation of Bile

physiology First Year

1. FUNCTIONs, Secretion and regulation OF BILE GROUP E

2. What is Bile? Bile is a bitter-tasting, dark green to yellowish brown fluid, produced by the liver . Bile aids the process of digestion of lipids in the small intestine . Bile is stored in the gallbladder and upon eating is discharged into the duodenum .

3. COMPOSITION OF BILE Daily secretion : 500 – 1000 ml Transparent alkaline fluid, light yellow in colour. pH : 7.8 – 8.6 Water Bile Salts – These are sodium & potassium salts of bile acid. Bile pigments –These are biliverdin & bilirubin

4. SECRETION OF BILE : Secretion occurs in three stages :- Formation & Secretion of constituents of bile by the liver: Bile salts are synthesized in hepatocytes and transferred into bile canaliculi . Bile salts along with glucose, amino acids and bile pigments are actively secreted into canaliculi .

5. B) Filling of gall bladder :- Bile then passes through the biliary tree and ultimately to the hepatic duct And then it reaches the gall bladder where it is concentrated and stored temporarily. Discharge of bile in intestine :- When there is chyme in the intestine sphincter of Oddi and sphincter of Boyden are relaxed and bile flows into the intestine. SECRETION CONTD.

6. ENTEROHEPATIC CIRCULATION : Entero-hepatic circulation is a continuous circulation of bile salts from liver to bile and there passage into the duodenum. Their absorption in the ileum and then return to the liver as a mixture of bile acids and salts. 95% of bile salts are reabsorbed by the small intestine 5% of bile salts are lost in feces (500 -600 mg /day

7. IN LIVER :- Bile acid dependent : Bile secretion increases as more and more bile acids are presented to the liver by enterohepatic circulation. It occurs after fatty meal. When intestine is empty this mechanism stops. Bile acid independent : It is mainly due to transfer of electrolytes by pumps(Na + - K + ATPase) It is under the influence of SECRETIN . REGULATION OF BILE :

8. IN THE INTESTINE :- Bile flows to intestine when sphincter of oddi is relaxed . It is increased further due to simultaneous contraction of gall bladder and occurs in response to meal This process involves parasympathetic impulses, CCK- Pz secretion and tone of duodenal wall which aid in flow of bile into intestine .

9. Liver : Secretin stimulates duct cells Gall bladder : CCK triggers contraction Duodenum : Intestinal phase stimuli Trigger secretion of CCK and Secretin . Sphincter of Oddi : CCK causes relaxation

10. FUNCTION OF BILE : 1. DIGESTIVE : - HELPS IN DIGESTION OF FATS 2. ABSORPTIVE : - HELPS IN ABSORPTION OF FAT, FAT SOLUBLE VITAMINS, IRON AND CALCIUM ETC. 3. LAXATIVE : - STIMULATE PERISTALISIS MOVEMENTS OF INTESTINE & THEREBY HELPS IN DEFECATION.

11. FUNCTIONS CONTD. 4. CHOLERETIC : - HELPS IN SECRETION OF BILE FROM LIVER 5. EXCRETORY : - CERTAIN SUBSTANCE LIKE HEAVYMETALS, CERTAIN DRUGS,BILE PIGMENTS AND EXCESS CHOLESTEROL 6. MUCIN OF BILE ACTS AS LUBRICANTS FOR CHYME IN INTESTINE

12. THANK YOU!