Bile secretion

Composition of Bile

Water  - 97.5%

Solids -  2.5%

Solids contains

Organic substances                          - Bile salts

                                                            Bile pigments

                                                            Cholesteros

                                                            Fatty acids

                                                            Lecithin

                                                            Mucin

In organic substances                          Sodium

                                                            Potassium

                                                            Calcium

                                                            Chlorides

                                                            Bicarbonates

 

Formation of biles

Bile is produced continuously y by hepatocytes

Bile drains into the hepatic ducts and is stored in the gallbladder for subsequent release

Choleretic agents increase the formation of bile

Bile is formed by the following process

Primary acids

Ex – Cholic acid and chenodeoxycholic acid are synthesized from cholesterol  by hepatocytes

Secondary bile acids

In the intestine , bacteria convert a portion of each of the primary bile acids to secondary bile acids (deoxycholic acid and lithocholic acid)

Synthesis of new bile acids occurs as needed , to replace bile acids that are excreted in the feces

The bile acids are conjugated with glycine or taurine to form their respective bile salts

Ex – Taurocholic acid is cholic acid conjugated with taurine

Electrolytes and H2O are added to the bile

During the interdigestive period m the gallbladder is relaxed the sphincter of Oddi is closed and the gallbladder fills with bile

The bile is concentrated in the gallbladder as a result of isosmotic absorption of solutes and H2O

 Contraction of gallbladder

CCK

It is released in response to small peptides and fatty acids in the duodenum

It tells the gallbladder that bile is needed to emulsify and absorb lipids in the duodenum

It causes contraction of the gallbladder and relaxation of the sphincter of Oddi

 Ach

It causes contraction of the gallbladder

 

Function of bile

1.Digestive function

2. Absorptive functions

3. Excretory function

Bile pigments are the major excretory products of the bile

The other substances excreted in bile are             

Heavy metals like copper and iron

Some bacteria like typhoid

 Some toxins

Cholesterol

Lecithin

4. Laxative action

5. Antiseptic action

Bile inhibits the growth of certain bacteria in the lumen of intestine by its natural

detergent action

6. Lubrication function

The mucin in bile acts as a lubricant for the chime in  intestine

7.Maintenance of PH in GIT

It is highly alkaline, it neutralizes the acid chime which enters the intestine from stomach.

The optimum PH is maintained for the action of digestive enzymes