DIGESTIVE PHYSIOLOGY

1. Liver and gall bladder
Vigneswaran Ganesan M.sc.,
Senior Lecturer
Department of Biochemistry

2. SYNOPSIS

3. LIVER
- largest gland in the
body
- weighs about 1.5kg in
man
- located in the upper
and right side of the
abdominal cavity
immediately beneath
the diaphragm
FUNCTIONAL ANATOMY OF LIVER
• Made up of hepatic lobes
• Each lobe consists of many lobules called hepatic lobules
Hepatic lobules
FUNCTIONS
Dual organ having both
secretory and excretory
function
Structural & Functional unit of liver
Honey comb like structure
Made up of liver cells called
HEPATOCYTES
Arranged in hepatic plates
Each plates made up of two columns of cells
In between two columns of each plate lies a
Bile canaliculus
In between the neighboring plates, a blood
space called sinusoid is present. Sinusoid is
lined by the endothelial cells. In between
the endothelial cells some special
macrophages called Kupffer cells are
present

4. PORTAL TRIADS
• Each lobule is surrounded by many portal triads. Each portal
triad consists of three vessels
1. A branch of hepatic artery.
2. A branch of portal vein.
3. A tributary of bile duct
• The branches of hepatic artery and portal vein open into the
sinusoid.
• Sinusoid opens into the central vein. Central vein empties into
hepatic vein.
• Bile is secreted by hepatic cells and emp tied into bile canaliculus.
From canaliculus, the bile enters the tributary of bile duct.
• The tributaries of bile duct from canaliculi of neighboring lobules
unite to form small bile ducts.
• These small bile ducts join together and finally form left and right
hepatic ducts which emerge out of liver

5. BILIARY SYSTEM
• Biliary system is also known as extrahepatic biliary apparatus.
• It is formed by gallbladder and the extrahepatic bile ducts (bile ducts
outside the liver).
• The right and left hepatic bile ducts which come out of liver join to form
common hepatic duct.
• It unites with the cystic duct from gallbladder to form common bile duct
• The common bile duct unites with pancreatic duct to form the common
hepatopancreatic duct or ampulla of Vater which opens into the
duodenum.
• There is a sphincter called sphincter of Oddi at the lower part of common
bile duct, before it joins the pancreatic duct. It is formed by smooth
muscle fibers of common bile duct.
• It is normally kept closed; so the bile secreted from liver enters gall
bladder where it is stored.
• Upon appropriate stimulation the sphincter opens and allows flow of bile
from gallbladder into the intestine

6. BLOOD SUPPLY TO LIVER

7. PROPERTIES AND COMPOSITION
OF BILE
Bile is a golden yellow or greenish fluid.
It enters the digestive tract along with pancreatic juice
through the common opening called ampulla of Vater.
PROPERTIES
Volume – 800 to 1200 mL/day
Reaction – alkaline
pH- 8 - 8.6
Specific gravity – 1.010 to 1.011

8. COMPOSITION OF BILE

9. SECRETION AND STORAGE OF BILE
Bile 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 passes through
canaliculi and hepatic ducts to reach common
hepatic duct.
From here it may enter the intestine or
gallbladder.
Sodium, bicarbonate and water are added to
bile when it passes through the ducts.
These substances are secreted by the epithelial
cells of the ducts.
The addition of sodium, bicarbonate and water
increases the total quantity of bile
When bile is stored in gallbladder, it
undergoes many changes both in quality
and quantity such as:
1. Volume is reduced because of absorption
of large amount of water and
electrolytes (except calcium and
potassium).
2. Concentration of bile salts, bile
pigments, cholesterol, fatty acids and
lecithin is increased because of
absorption of water.
3. The pH is slightly decreased.
4. Specific gravity is increased.
5. Mucin is added

11. BILE SALTS
• Bile salts are the sodium and potassium salts of bile acids,
which are conjugated with glycine or taurine. Bile salts are
formed in liver
FORMATION OF BILE SALTS
• formed by primary bile acids
Cholic acid deoxycholic acid
Chenodeoxycholic acid lithocholic acid

12. FUNCTIONS OF
BILE SALTS
1. Emulsification of fats
2. Absorption of fats
3. Choleretic action
4. Cholagogue action
5. Laxative action
6. Prevention of gall stone
formation
• Choleretic – bile salts stimulate the
secretion of bile from liver.
• Cholagogue - Cholagogue is an agent,
which causes contraction of gallbladder
(CCK) and release of bile into the
intestine.
• Laxative is an agent which induces defe
cation. Bile salts act as laxatives by
stimu lating peristaltic movements of
the intestine

13. BILE PIGMENTS
Bile pigments are the excretory products in bile. Bilirubin and biliverdin are the
two bile pigments and bilirubin is the major bile pigment in human being.
The bile pigments are formed during the breakdown of hemoglobin, which is
released from the destroyed RBCs in the reticuloendothelial system

14. FORMATION AND EXCRETION OF
BILE PIGMENTS

15. BILE
FUNCTIONS
1. Digestive Function
2. Absorptive Function
3. Excretory Function
4. Laxative Action
5. Antiseptic Action
6. Choleretic Action
7. Maintenance Of PH In GIT
8. Prevention Of Gallstone Formation
9. Lubrication Function
10. Cholagogue Action

16. LIVER
Liver is the largest gland
and one of the vital organs of
the body. It performs many
vital metabolic and
homeostatic functions
FUNCTIONS
1. Metabolic function
2. Storage function
3. Synthetic function
4. Secretion of bile
5. Excretory function
6. Heat production
7. Hemopoietic function
8. Hemolytic function
9. Inactivation of hormones and drugs
10. Defensive and detoxification functions

17. GALL
BLADDER
Bile secreted from the liver is
stored
capacity 50mL (approx)
not essential for life
FUNCTIONS
1. Storage of bile
2. Concentration of bile
3. Alteration of pH of bile
4. Secretion of mucin
5. Maintenance of pressure in biliary system

18. REGULATION OF BILE
SECRETION
Bile secretion is a continuous process though the amount may
be less during fasting.
It starts increasing 3 hours after the meals.
Secretion of bile from the liver and release of bile from the
gallbladder are influenced by some chemical factors which are
categorized into three groups:
1. Choleretics.
2. Cholagogue.
3. Hydrocholeretic agents

19. APPLIED PHYSIOLOGY

20. APPLIED PHYSIOLOGY

21. APPLIED
PHYSIOLOGY
• GALL STONES
Gallstone is a solid crystal
deposit that is formed by
cholesterol, calcium ions and
bile pigments in the
gallbladder or bile duct.
Cholelithiasis is the presence
of gallstones in gallbladder.
• FORMATION – Precipitates in
the mucosa of gall bladder as a
crystals. Bile pigments and calcium
are attached to these crystals and
results in gallstones.
• Causes
1. Reduction in bile salts.
2. Excess of cholesterol or disturbed
cholesterol metabolism
3. Excess of calcium ions due to
increased concentration of bile.
4. Damage or infection of gallbladder
epithelium.
5. Obstruction of bile flow from the gall
bladder