HISTOLOGY OF LIVER and
BILIARY TRACT
LEARNING OBJECTIVES
At the end of session the student should be able to;
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Identify the important landmarks of liver,
Know the basic histological architecture of liver,
Identify the structural details of hepatocytes, portal triad, hepatic sinus,
hepatic lobule
Discuss the different components of biliary tract
Identify the histological appearance of gall bladder
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OVERVIEW; LIVER
Surrounded by GLISSON CAPSULE.
Septas divide the liver parenchyma into lobes and lobules.
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LIVER LOBULE
Hexagonal mass of tissue composed of plates of hepatocytes.
Hepatocytes radiate like spokes from central vein.
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LIVER LOBULE
hepatocytes radiate outward from a central vein (CV) in the center
At the vertices of the lobule are regularly distributed portal triads (also
known as portal tracts).
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PORTAL TRIAD
Areas of CT b/w lobules containing branches of portal vein, hepatic
artery, bile duct and lymphatic vessels.
LIVER SINUSOIDS
Sinusoids are low pressure vascular channels that receive blood from
terminal branches of the hepatic artery and portal vein at the periphery
of lobules and deliver it into central veins.
Sinusoids are lined with endothelial cells and flanked by plates of
hepatocytes
Fenestrations.
The space between sinusoidal endothelium and hepatocytes is called
the space of Disse.
Sinusoids are populated by numerous Kupffer cells, a type of fixed
macrophage
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SPACE OF DISSE
Subendothelial space b/w hepatocytes and sinusoidal lining cells.
Contains microvilli of hepatocytes,reticular fibers and occ. Non
myelinated nerve fibers.
Function _ exchange of metabolites.
Blood does not come in contact with hepatocytes.
PORTAL LOBULE
Triangular region apices of which are formed by central vein and
centre is marked by portal area.
Contains portions of three adjacent liver lobules.
Lobule is defined in terms of bile flow.
HEPATOCYTE
Large polyhedral cells with central rounded nuclei.
Dispersed chromatin.
Fine brown lipofusin pigments.
hepatocytes are arranged in plates that anastomose with one another.
The cells are polygonal in shape and their sides can be in contact either
with sinusoids (sinusoidal face) or neighboring hepatocytes (lateral
faces).
A portion of the lateral faces of hepatocytes is modified to form bile
canaliculi.
BILIARY TRACT
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BILIARY TRACT
The daily basal secretion of bile is approximately 500 mL.
The bile produced by the hepatocyte flows through the bile canaliculi,
bile ductules, and bile ducts.
These structures gradually merge, forming a network that converges to
form the right and left hepatic ducts, which unite to form the common
hepatic duct.
The common hepatic duct, after receiving the cystic duct from the
gallbladder, continues to the duodenum as the common bile duct
(ductus choledochus).
BILIARY TRACT HISTOLOGY
The hepatic, cystic, and common bile ducts are lined with a mucous
membrane of simple columnar epithelium.
The lamina propria is thin and is surrounded by an inconspicuous layer
of smooth muscle.
This muscle layer becomes thicker near the duodenum and finally, in the
intramural portion, forms a sphincter that regulates bile flow (sphincter of
Oddi).
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CONTROL OF SECRETION OF BILIARY TRACT
The flow of bile and pancreatic juice into the duodenum is controlled by
the complex arrangement of smooth muscle known as the sphincter of
Oddi.
The components of this structure include the choledochal sphincter at
the distal end of the common bile duct, the pancreatic sphincter at the
end of the pancreatic duct and a meshwork of muscle fibres around the
ampulla.
GALL BLADDER
The gallbladder is a hollow, pear-shaped organ attached to the lower
surface of the liver. It can store 30 to 50 ml of bile.
The wall of the gallbladder consists of four layers:
1. Mucosa
2. Muscularis Externa
3. Perimuscular connective tissue
4.Serosa / Adventitia
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MUCOSA
The wall of a gall bladder in the non-distended state in which the mucosa
is thrown up into many folds
Mucosal Lining consists of Simple columnar epithelium
At high magnification, the simple epithelial lining of the gall bladder is
seen to consist of very tall columnar cells with basally located nuclei;
numerous short irregular microvilli account for the unevenness of the
luminal surface.
Lamina propria, consists of connective tissue, blood vessels and
lymphatic vessels
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MUSCULARIS EXTERNA
The fibres of the muscular layer are arranged in longitudinal,
transverse and oblique orientations.
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SEROSA / ADVENTITIA
Externally, there is a thick collagenous adventitial (serosal) coat
conveying the larger blood and lymphatic vessels.
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CHOLELITHIASIS
Abnormal concentration and precipitation of the constituents of bile may
form stones (calculi) within the gall bladder or the extrahepatic biliary
system.
A stone may become impacted in a duct, leading to blockage. Complete
blockage of the common bile duct by a stone would lead to failure of bile
secretion and clinical jaundice.
If the gall bladder is affected by stones then it may become inflamed
leading to pain (chronic cholecystitis).
The term cholelithiasis is used to refer to formation of stones within the
biliary system.
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