HISTOLOGY OF LIVER DR. AKANKSHA SINGH - PowerPoint Presentation

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HISTOLOGY OF LIVER

DR. AKANKSHA SINGH

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LIVER HISTOLOGY

Largest gland of the body.

Present under diaphragm and occupies the entire right

hypochondrium

, part of

epigastrium

and left

hypochondrium

.

Functions – synthesis of urea , formation and secretion of bile, detoxification of metabolic wastes, storage of glycogen, metabolism of

cholestrol

and fat, synthesis of plasma proteins etc.

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Histology of liver

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C

lassic lobule

It forms

the structural and functional unit of the organ.

Hexagonal in shape.

It has a vein at the centre, the

central vein

Portal tracts in the periphery.

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LIVER ACINUS

It is the

functional unit of the liver.

Diamond shaped.

At the two opposite angles of the diamond shaped

acinus

are

central veins

and at the other two opposite site angles are

portal triads

.

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RAPPAPORT’S CLASSIFICATION OF LIVER (Very important)

The

acinus

is

devided

into 3 zones according to

distance from the blood supply:

Zone1

:

hepatocytes

are closest to blood vessels and they are

best oxygenated

.

Zone2

:

less oxygenated

than zone1.

Zone 3

: which is farthest from blood vessels (near the central vein) has the

poorest oxygen supply

.

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Liver histology

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PORTAL TRIADS-

It consists of

portal vein, bile duct and hepatic artery.

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Space of Disse

and MALL

The space of Mall is a primary component of the digestive system. This is due to the fact that 

bile

produced

by the liver is collected here. Ducts draining the bile manufactured by the liver are surrounded by a mesh of tiny branches of the hepatic artery. Blood flowing from the hepatic artery goes through this space before draining off into the portal veins, while the bile flows out through the bile ducts to the 

small intestine

, with some stored in the gallbladder.

The space of

Disse

is a smaller continuation of the space of Mall. This smaller space is located between individual liver cells and tiny 

blood vessels

. While the space of Mall enables exchange of arterial and venous blood, along with bile collection and transport out of the liver, the space of

Disse

provides nutrition to individual liver cells. It does this by

perfusing

proteins and other cell nutrition substances from adjacent arterial vessels directly into liver cells, where they are absorbed.

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PANCREAS

Retroperitoneal organ.

Extends from the concavity of the duodenum to the

hilum

of the spleen.

Microscopic features: it has 3 components:

stroma

, parenchyma, and duct system.

stroma

:

the gland is covered with

a thin capsule of connective tissue.

From the capsule numerous septa arise which divide the parenchyma of the gland into lobules.

Parenchyma-

having

exocrine and endocrine parts

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Exocrine part and duct system

Pancreatic

acini

-

pyramidal shaped cells

with a

small lumen

having

rounded nuclei

at its base.

Cytoplam

is

eosinophilic

at apex

nd

basophilic near the base of the cells

(like parotid gland)

Duct

System-

small duct-

intralobular

duct

lined by

simple

cuboidal

epithelium

and larger duct –

interlobar

duct

lined by

columnar epithelium.

Cenroacinar

cells –

are seen at the centre of the

acini

where duct system begins. Having central nucleus and pale cytoplasm.

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ENDOCRINE PARTS

ISLETS OF LANGERHANS-

Polyhedral cells, arranges in irregular cords. In between the cords there are capillaries.

(

characterstic

feature)

Islet of

langerhans

have 4 types of cells: Alpha, beta,

delta,PP

Cells.

Beta cells are located in the centre of islets, alpha and delta cells are in the periphery and PP CELLS are found throughout the islets.

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Gall bladder

(

no

muscularis

mucosa and

submucosa

)

Simple columnar epithelium

Lamina

propria

Muscularis

externa

adventitia

serosa

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Blind sac, present at inferior surface of the liver.

Microscpic

features- from lumen to outside-

Mucosa

:

mucosa has numerous folds.

Lining epithelium

–

simple columnar epithelium with

no goblet cells,

lies over lamina

propria

. Epithelial cells have

microvilli

.

No

musculars

mucosa (imp)

Muscularis

externa

–

smooth muscles are

arreanged

in circular, longitudinal and oblique manner. Numerous collagen and elastic fibers.

Adventitia and

serosa

No

submucosa

in gall bladder.(imp)

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Important questions

What is?

(liver histology very imp for

theroy

exams as well)

1) Classic lobule, portal lobule, liver

acinus

2)

Rappaport’s

classification of liver

3) Space of

disse

and mall

4) Islets

of

langerhans