Bile juice

Bile is a bitter-tasting, dark green to yellowish brown fluid, produced by the liver , it is stored in the gallbladder and upon eating is discharged into the duodenum. .
The principal function of the gallbladder is to serve as a storage reservoir for bile.
The main components of bile are water, bile salts, bile pigments, and cholesterol
Bile salts act as emulsifying agents in the digestion and absorption of fats. Cholesterol and bile pigments from the breakdown of hemoglobin are excreted from the body in the bile.
Physical properties;
Hepatic bile: pH 7.4, colour is golden yellow ,
Bladder bile: pH 6.8, color is green dark to yellow (darker)
Volume of bile produced reaches to one liter of bile per day (depending on body size).

1. Bile Juice
•Bile is a bitter-tasting, dark green to yellowish brown fluid, produced by
the liver , it is stored in the gallbladder and upon eating is discharged into
the duodenum. .
•The principal function of the gallbladder is to serve as a storage reservoir
for bile.
•The main components of bile are water, bile salts, bile pigments, and
cholesterol
•Bile salts act as emulsifying agents in the digestion and absorption of fats.
Cholesterol and bile pigments from the breakdown of hemoglobin are
excreted from the body in the bile.
•Physical properties;
•Hepatic bile: pH 7.4, colouris golden yellow ,
•Bladder bile: pH 6.8, color is green dark to yellow (darker)
•Volume of bile produced reaches to one liter of bile per day (depending on
body size).

2. Bile Juice
•Bile Composition;
•Water (85%),
•bile salts (10%),(Cholic, chenodeoxycholic, deoxycholic, and
lithocholic acid)
•mucus
•pigments (3%), bile pigments e.g bilirubin glucuronide
•fats (1%),such as Phospholipids (lecithin) , cholesterol.
•0.7% inorganic salts.

3. Bile secretion
•Bile is secreted in two stages ;
Stage one; the liver hepatocytes will secret an initial secretion that is rich in
bile salts , cholesterol, and other organic components, the initial secretion
will drain through the many minute bile canaliculi that penetrate the
liver.
Stage Two ; The initial secretion will flow towards the bile ducts , during its
flow in the ducts a secondary secretion is added to the initial bile which is
a watery solution of sodium bicarbonate ions.
The bile then will either empty into the duodenum when the sphincter of
Oddi is open,
Or( when the sphincter of Oddi is closed) it will be prevented from draining
into the intestine and instead flows into the gallbladder, where it is stored
and concentrated to up to five times its original potency . This
concentration occurs through the absorption of water sodium , chloride
and other electrolytes, while retaining and concentrating all the original
organic molecules.

4. Bile secretion

5. Bile secretion stimulation
•1-Under neural control mediated by e.g acetyl choline.
•2-Under hormonal control ;
When food is released by the stomach into the duodenum in the
form of chyme, the duodenum releases cholecystokinin,
which is the main stimulant causing the gallbladder to release
the concentrated bile to complete digestion.
-Gastrin andsecretin also stimulate bile secretion.
•Lack of bile salts in the enterohepatic circulation stimulates
bile synthesis and secretion.

6. Enterohepatic Circulation
•About 95% of the salts secreted
in bile are reabsorbed actively in
the terminal ileumand re-used.
Blood from the ileum flows
directly to the hepatic portal vein
and returns to the liver where the
hepatocytes reabsorb the salts
and return them to the bile ducts
to be re-used, sometimes two to
three times with each meal.

7. Function of bile juice
•1-It is important in the digestion and absorption of lipids;
Bile acts as a surfactant , helping to emulsify the fats in the food. Bile salt
anions have a hydrophilic side and a hydrophobic side, and therefore
tend to aggregate around droplets of fat ( triglycerides and phosphiolipids
) to form micelles, with the hydrophobic sides towards the fat and
hydrophilic towards the outside. The hydrophilic sides are positively
charged due to the lecithin and other phospholipids that compose bile,
and this charge prevents fat droplets coated with bile from re-aggregating
into larger fat particles. The dispersion of food fat into micelles thus
provide a largely increased surface area for the action of the enzyme
pancreatic lipase thus aiding in the digestion of lipids.,

8. Function of bile juice
•2-Bile serves as the route of excretion for bilirubin.
•3-The alkaline bile has the function of neutralizing any excess
stomach acid before it enters the ileum.
•4-. Bile salts also act as bactericides, destroying many of the
microbes that may be present in the food.

9. Abnormalities associated with bile
•Gall stone ; The majority of gall stones are made up of
cholesterol , (cholesterol tends to accrete into lumps in the
gallbladder)
•Causes of gall stones;
•-Too much absorbtion of water from the bile .
•-Too much cholesterol in bile.
•-Inflammation of the epithelium.

10. Secretionofthe small intestine
*Intestinal glands
Brunner’s gland(basic mucus)
Lieberkuhn Crypt(main part)
*Nature, Compositions & functions
pH 7.6, iso-osmotic solution, 1~3
L/day
Enterokinase,the only one secreted
Oligopeptidase,oligosaccharidase
those
contained in the epithelial cells
*Regulation of secretion of small
intestine
Mainly through plexus reflex
initiated by
inflation of the intestine

11. *Control of bile secretion & gallbladder
emptying
Nervous regulation
Vagus nerve: ACh, gastrin
Hepatic bile secretion(small amounts)
Gallbladder contraction(slightly)
Humoral reulation
Gastrin:direct to hepatic cells &
gallbladder;
indirect to stomachHClsecretin 
Secretin:act to bile duct & not to hepatic
cells,
so: H
2O & HCO
3

, bile salt ()
Cholecystokinin (CCK):gallbladder
contraction & Oddi’s sphincter
dialation
Bile salt:enterohepatic circulation of bile
salt

12. Bilesecretion&gallbladder emptying
*Nature, Compositions & functions
Hepatic bile: pH 7.4, golden yellow
Bladder bile: pH 6.8, color become
darker
Compositions:H
2O, ions, bile acid, bile
pigment, fatty acid, cholesterol,
lecithin,
mucoprotein, etc., but no enzyme
Functions of bile (mainly by bile salt):
Fat emulsification; lipid absorption;
Promote the absorption of fat-soluble
Vits

14. §4. Digestion in the intestine
Pancreatic juice& its secretion
*Nature, Compositions & functions
pH 7.8~8.4, colorless & odourless, 1~2
L/day
Bicarbonate (HCO
3

)
Neutralize HCl & provide a weak basic
medium favoring digestive enzyme
action
Pancreatic enzymes: amylase, lipase,
colipase,
trypsinogen & chymtrypsinogen, etc.
Turn trypsinogen into trypsin by
entero-
kinase, turn chymtrypsinogen into
chym-
trypsin by trypsin
Trypsin inhibitor: a polypeptide