Download MBBS Digestive System III Lecture PPT

Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Digestive System III Lecture PPT


DIGESTIVE SYSTEM III

HISTOLOGY OF LIVER, GALL BLADDER

AND PANCREAS


HISTOLOGY OF LIVER
INTRODUCTION

? 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.
? Liver is surrounded by thin connective tissue

capsule called Glisson's capsule.

? Glisson's capsule thickened at the porta hepatis and

sends trabeculae into the interior dividing

parenchyma into lobules.

? These trabeculae carry branches of hepatic artery,

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

functional unit of liver.

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

(hepatocytes) separated by sinusoids.

? At the periphery of each lobule there are several

portal triad.

? Central vein in the centre of each lobule and drain

blood from lobules into hepatic vein.

? Bile canaliculi: spaces present between plasma

membrane of adjacent liver cells.



Different types of liver lobules

A.Classical liver

lobule

B. Portal liver

lobule

C. Liver acinus
? Hepatocytes (liver cells)
? Shape--polygonal
? 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).
? Liver cells has 5-12 sides, some sides exposed to

sinusoids and other sides shows infolding between

adjacent cells to form bile canaliculi.

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

hepatocytes.

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

sinusoids

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


? Bile canaliculi
? Smallest branches of the biliary tree.
? They empty into bile canals of Hering composed of

cuboidal epithelium (cholangiocytes).

? Bile canal merge to form bile ductules
? Bile ductules merge, enlarge, and form right and

left hepatic ducts leaving the liver.

? Into the canaliculi hepatocytes continuously secrete

bile.

GALL BLADDER

? Gall bladder is temporary storehouse of bile

and concentrate it by water re-absorption.

? Layers of gall bladder--
a) Mucosa
b) Fibromuscular layer
c) Serosa/adventitia
? Mucosa--
? Lining epithelium simple columnar epithelium.
? These cells have many small microvilli on their

apical surface.

? These cells involved in absorption of water from

stored bile.

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

submucosa are absent.

? Fibromuscular layer--
? Composed of randomly arranged smooth

muscles.

? In between muscles fibre is dense connective

tissue that is rich in elastic fibres.

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

by adventitia.


PANCREAS

? Mixed gland i.e.

consists of an

exocrine &

endocrine portion.

? Exocrine part:

secretes pancreatic

juice.

? Endocrine part:

secretes hormones.
Histology of Exocrine Pancreas

? Covered with a capsule.
? Septas arise from capsule which divide the

gland into many small lobules.

? Interlobular connective tissue contains large

ducts, blood vessels & nerve fibres.

? Interlobular connective tissue surrounds the

acini, small ducts & islets of Langerhans.

? Pancreatic Acini--
? Serous in nature.
? Lined by pyramidal cells and have small lumen.
? Acinar cells--
supranuclear region is filled with zymogen granules.
Infranuclear region is intensely basophilic.
? Extensive duct system--
intralobular (intercalated), interlobular & main duct.
? Acinar lumen may show pale staining cells of

intercalated duct (centroacinar cells).

Histology of Endocrine Pancreas

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

plates.

? Islets contain 4 types of cells:
? A(alpha) cells--20% , secrete glucagon
? B (beta) cells--70% , secrete insulin
? D (delta) cells--5% , secrete somatostatin
? F or PP cells-- secrete pancreatic polpetides



Self Assessement

1] Which of the following cell is responsible for

myelination of axon in CNS ?

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

3.] White pulp of spleen can be identified

differentially from the lymphatic nodule of lymph

node by the presence of

(a) Germinal centre
(b) Corona
(c) Central arteriole
(d) Lymphocytes
4.]Hassall's corpuscles are present in
(a) Lymph node
(b) Spleen
(c) Thymus
(d) Tonsil

5.]Crypts of palatine tonsil are lined by
(a) Simple squamous epithelium
(b) Stratified squamous nonkeratinized epithelium
(c) Pseudostratified columnar epithelium
(d) Stratified squamous keratinized epithelium
6.] All of the following layers are present in

epidermis of THIN SKIN except ?

a) Stratum basale

b) Stratum spinosum

c) Stratum lucidum

d) Stratum corneum

7.] Thin skin is characterised by the presence of

(a) Thin epidermis

(b) Hair follicle

(c) Sebaceous gland

(d) All of the above
8.] Lining epithelium of trachea ?
a) Simple sqamous
b) Simple columnar
c) Pseudostratified ciliated columnar
d) Stratified squamous non-keratinized

9.] Blood-air barrier is formed by all except ?
a)Endothelium of capillary
b)Lining epithelium of alveolus
c)Fused basal lamina of endothelium and

epithelium

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

respiratory tract?

a) Trachea
b) Bronchus
c) Epiglottis
d) None
? 1.Ans: b) Oligodendrocytes
? 2.Ans (b) Paracortex
? 3.Ans (c) Central arteriole
? 4 Ans (c) Thymus
? 5 Ans (b) Stratified squamous

nonkeratinized epithelium

? 6. Ans(c) Stratum lucidum
? 7.Ans(d) All of the above
? 8.Ans (c) Pseudostratified ciliated columnar
? 9.Ans (d) Only endothelium of capillary
? 10.Ans(c) Epiglottis

This post was last modified on 30 November 2021