Bile is a thick, yellow-green fluid produced by the liver that aids in fat digestion. It is composed primarily of water, bile salts, bile pigments, cholesterol, and fatty acids. Bile is stored and concentrated in the gallbladder before being released into the small intestine in response to food. In the intestine, bile salts act to emulsify and absorb fats, stimulate bile secretion from the liver, and induce bowel movements. Bile also plays roles in excreting waste, maintaining pH, preventing gallstone formation, and lubricating the intestines.

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

2. bile

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

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

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

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

10. Storage of bile
1) Most of the bile from the liver enters the gallbladder,where it is stored.
2) The capacity of gallbladderis approximately 50mL
3) It is released from gallbladder into the intestinewhenever it is required.
4) 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

11. Difference between liver bile and gallbladder bile
Hepatic bile Gallbladderbile
1) Bile is produced by the liver 1)Bile is stored in the liver
2) Flows into the gallbladderfor storage in the
absence of food
2)Secreted into the smallintestinein 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) Slightlyacidic
6)Enters the common bile ducts through the
left and right hepatic ducts
6)Enters the common bile ducts through the
cysticduct

12. Bile salts
• Bile salts are the sodium and potassium salts of the bile acids, which are conjugatedwith
glycine ortaurine.

13. 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) Absorptionn 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.
3) Choleretic action
Bile salts stimulate the secretion of bile from liver. This action is called
choleretic action.

14. 4) 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.
5) Laxative action
Laxative is an agent which induces defecation. Bile salts act as laxatives by stimulating peristaltic
movements of the intestine.
6) Preventionn 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.

15. Bile pigments
1) Bile pigments are the excretory products of bile.
2) Bilirubin and Biliverdin are the two bile pigments.
3) Bile pigments are formed during the breakdown of hemoglobin.
Formation and excretion of bile pigments

16. Functions of bile
1) Digestive function
2) Absorptive function
3) 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.

17. 4) Laxative function
5) Antiseptic action
6) Choleretic action
7) 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.
8) Prevention of gallstone formation
9) Lubrication function
The mucin in bile acts as a lubricant for the chyme in intestine.
10) Cholagogue action