bile.pptx

Bile

1. Bile Presented by, D.Ragavi , M.Sc.Biochemistry .

2. bile

3. Bile Bile is also know n as gall it is a thick –sticky and golden yellow to green color fluid is produced by the liver. Bile is a digestive juice. Main function of bile is to breakdown the fats into fatty acid . It is stored in the gallbladder .

4. Properties of bile Volume : 800 to 1,200 mL/day Reaction : alkaline pH : 8 to 8.6 Specific gravity : 1.010 to 1.011 Color : Golden yellow or green

5. Composition of bile Bile Water-97.6% Solids-2.4% Organic substance Inorganic substance Bile salts Bile pigments Cholesterol Fatty acid Lecithin Mucin 1.Sodium 2.Calcium 3.Potassium 4.Chloride 5.Bicarbonate

6. Secretion of bile B ile is secreted by hepatocytes . The initial bile secreted by hepatocytes contains large quantity of bile acids, bile pigments, cholesterol, lecithin and fatty acids. From hepatocytes, bile is released into canaliculi. From here, it passes through small ducts and hepatics ducts and reaches the common hepatic ducts. From common hepatic duct, bile is diverted either directly into the intestine or into the gallbladder. Sodium , bicarbonate and water are added to bile when it passes through the ducts. These substance are secreted by the epithelial cells of the ducts . Addition of sodium, bicarbonate and water increases the total quantity of bile.

7. Storage of bile Most of the bile from the liver enters the gallbladder, where it is stored. The capacity of gallbladder is approximately 50mL It is released from gallbladder into the intestine whenever it is required. When bile is stored in gallbladder, it undergoes many changes both in quality and quantity such as: Volume is decreased Concentration of bile salts, bile pigments, cholesterol, fatty acids and lecithin is increased The pH is decreased slightly Specific gravity is increased Mucin is added to bile

8. Difference between liver bile and gallbladder bile Hepatic bile Gallbladder bile 1) Bile is produced by the liver 1 )Bile is stored in the liver 2) Flows into the gallbladder for storage in the absence of food 2)Secreted into the small intestine in the presence of the food 3)Readily secreted form of bile from the liver 3) Stored form of bile in the gallbladder 4)Not concentrated 4) Concentrated 5)Alkaline 5) Slightly acidic 6)Enters the common bile ducts through the left and right hepatic ducts 6)Enters the common bile ducts through the cystic duct

9. Bile salts Bile salts are the sodium and potassium salts of the bile acids, which are conjugated with glycine or taurine.

10. Functions of bile salts 1) Emulsification of fats Emulsification is the process by which the fat globules are broken down into minute droplets and made in the form of a milky fluid called emulsion in small intestine, by the action of bile salts. 2) Absorption n of fats Bile salts help in the absorption of digested fats from intestine into blood. Bile salts combine with fats and make complexes of fats called micelles. The fats in the form of micelles can be absorbed easily. Cholereti c action Bile salts stimulate the secretion of bile from liver. This action is called choleretic action.

11. Cholagogue action Cholagogue is an agent which causes contraction of gallbladder and release of bile into the intestine. Bile salts act as cholagogues indirectly by stimulating the secretion of hormone cholecystokinin. This hormone causes contraction of gallbladder, resulting in release of bile. Laxative action Laxative is an agent which induces defecation. Bile salts act as laxatives by stimulating peristaltic movements of the intestine. Prevention n of gallstone formation Bile salts prevent the formation of gallstone by keeping the cholesterol and lecithin in solution. In the absence of bile salts, cholesterol precipitates along with lecithin and forms gallstone.

12. Bile pigments Bile pigments are the excretory products of bile . Bilirubin and Biliverdin are the two bile pigments. Bile pigments are formed during the breakdown of hemoglobin. Formation and excretion of bile pigments

13. Functions of bile Digestive function Absorptive function Excretory function Bile pigments are the major excretory products of the bile. Other substances excreted in bile are: i. Heavy metals like copper and iron ii . Some bacteria like typhoid bacteria iii. Some toxins iv . Cholesterol v. Lecithin vii . Alkaline phosphatase.

14. 4) Laxative function Antiseptic action Choleretic action Maintenance of pH in gastrointestinal tract As bile is highly alkaline, it neutralizes the acid chyme which enters the intestine from stomach. Thus, an optimum pH is maintained for the action of digestive enzymes. Prevention of gallstone formation Lubrication function The mucin in bile acts as a lubricant for the chyme in intestine. 10) Cholagogue action