Download MBBS Digestive System III Lecture PPT

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AND PANCREAS


HISTOLOGY OF LIVER
INTRODUCTION

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? Liver is the largest internal organ.
? In adults weight-- 1.5 kg (2% of the body weight).
? Location--Right upper quadrant of the abdomen.
? Dual blood supply--Portal vein and hepatic artery.

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? Liver is surrounded by thin connective tissue

capsule called Glisson's capsule.

? Glisson's capsule thickened at the porta hepatis and

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sends trabeculae into the interior dividing

parenchyma into lobules.

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? These trabeculae carry branches of hepatic artery,

portal vein, and bile duct.
? Liver lobules:
? Hexagonal areas that form the structural &

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functional unit of liver.

? Scanty connective tissue between lobules.
? Each lobule is made up of cords of liver cells

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(hepatocytes) separated by sinusoids.

? At the periphery of each lobule there are several

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portal triad.

? Central vein in the centre of each lobule and drain

blood from lobules into hepatic vein.

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? Bile canaliculi: spaces present between plasma

membrane of adjacent liver cells.

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Different types of liver lobules

A.Classical liver

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lobule

B. Portal liver

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lobule

C. Liver acinus
? Hepatocytes (liver cells)
? Shape--polygonal

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? Nucleus--Large, round &central (may binucleated).
? Consitute about 80% of liver volume.
? Life span about 5 months.
? Capable of regeneration.
? Forms hepatic cords (may branch & anastomose).

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? Liver cells has 5-12 sides, some sides exposed to

sinusoids and other sides shows infolding between

adjacent cells to form bile canaliculi.

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? Hepatic sinusoid--
? Vascular channels between the plates of

hepatocytes.

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? Lined by endothelial and phagocytic (kupffer) cells.
? The venous and arterial blood mixes in hepatic

sinusoids

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? Space of Disse (perisinusoidal space)--
Between sinusoidal endotheilum and hepatocytes.
? Ito cells (hepatic stellate cells)--
Found in perisinusoidal spaces.

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Involeved in storage of vitamin A and lipid


? Bile canaliculi
? Smallest branches of the biliary tree.

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? They empty into bile canals of Hering composed of

cuboidal epithelium (cholangiocytes).

? Bile canal merge to form bile ductules

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? Bile ductules merge, enlarge, and form right and

left hepatic ducts leaving the liver.

? Into the canaliculi hepatocytes continuously secrete

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bile.

GALL BLADDER

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? Gall bladder is temporary storehouse of bile

and concentrate it by water re-absorption.

? Layers of gall bladder--

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a) Mucosa
b) Fibromuscular layer
c) Serosa/adventitia
? Mucosa--
? Lining epithelium simple columnar epithelium.

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? These cells have many small microvilli on their

apical surface.

? These cells involved in absorption of water from

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stored bile.

? Lamina propria is present.
? Mucosal gland, muscularis mucosae and

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submucosa are absent.

? Fibromuscular layer--
? Composed of randomly arranged smooth

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muscles.

? In between muscles fibre is dense connective

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tissue that is rich in elastic fibres.

? Serosa--
? Inferior surface is covered by serosa and rest is

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by adventitia.


PANCREAS

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? Mixed gland i.e.

consists of an

exocrine &

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endocrine portion.

? Exocrine part:

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secretes pancreatic

juice.

? Endocrine part:

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secretes hormones.
Histology of Exocrine Pancreas

? Covered with a capsule.

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? Septas arise from capsule which divide the

gland into many small lobules.

? Interlobular connective tissue contains large

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ducts, blood vessels & nerve fibres.

? Interlobular connective tissue surrounds the

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acini, small ducts & islets of Langerhans.

? Pancreatic Acini--
? Serous in nature.
? Lined by pyramidal cells and have small lumen.

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? Acinar cells--
supranuclear region is filled with zymogen granules.
Infranuclear region is intensely basophilic.
? Extensive duct system--
intralobular (intercalated), interlobular & main duct.

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? Acinar lumen may show pale staining cells of

intercalated duct (centroacinar cells).

Histology of Endocrine Pancreas

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? In the form of "islands": Islets of Langerhans
? Scattered among the acini of exocrine part.
? Cells of islets are arranged as anastomosing

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plates.

? Islets contain 4 types of cells:
? A(alpha) cells--20% , secrete glucagon
? B (beta) cells--70% , secrete insulin

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? D (delta) cells--5% , secrete somatostatin
? F or PP cells-- secrete pancreatic polpetides

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Self Assessement

1] Which of the following cell is responsible for

myelination of axon in CNS ?

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a) Astroccytes
b) Oligodendrocytes
c) Microglia
d) Schwan cells

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2.] Thymus-dependent zone of a lymph node is
(a) Cortex
(b) Paracortex
(c) Medullary cords
(d) Medullary sinuses.

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3.] White pulp of spleen can be identified

differentially from the lymphatic nodule of lymph

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node by the presence of

(a) Germinal centre
(b) Corona
(c) Central arteriole

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(d) Lymphocytes
4.]Hassall's corpuscles are present in
(a) Lymph node
(b) Spleen
(c) Thymus

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(d) Tonsil

5.]Crypts of palatine tonsil are lined by
(a) Simple squamous epithelium
(b) Stratified squamous nonkeratinized epithelium

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(c) Pseudostratified columnar epithelium
(d) Stratified squamous keratinized epithelium
6.] All of the following layers are present in

epidermis of THIN SKIN except ?

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a) Stratum basale

b) Stratum spinosum

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c) Stratum lucidum

d) Stratum corneum

7.] Thin skin is characterised by the presence of

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(a) Thin epidermis

(b) Hair follicle

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(c) Sebaceous gland

(d) All of the above
8.] Lining epithelium of trachea ?
a) Simple sqamous

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b) Simple columnar
c) Pseudostratified ciliated columnar
d) Stratified squamous non-keratinized

9.] Blood-air barrier is formed by all except ?

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a)Endothelium of capillary
b)Lining epithelium of alveolus
c)Fused basal lamina of endothelium and

epithelium

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d) only endothelium of capillary
10.] Elastic cartilage is present in which part of

respiratory tract?

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a) Trachea
b) Bronchus
c) Epiglottis
d) None

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? 1.Ans: b) Oligodendrocytes
? 2.Ans (b) Paracortex
? 3.Ans (c) Central arteriole
? 4 Ans (c) Thymus
? 5 Ans (b) Stratified squamous

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nonkeratinized epithelium

? 6. Ans(c) Stratum lucidum
? 7.Ans(d) All of the above

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? 8.Ans (c) Pseudostratified ciliated columnar
? 9.Ans (d) Only endothelium of capillary
? 10.Ans(c) Epiglottis