DIGESTIVE SYSTEM III
HISTOLOGY OF LIVER, GALL BLADDER
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AND PANCREASHISTOLOGY 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 tissuecapsule 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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lobuleC. Liver acinus
? Hepatocytes (liver cells)
? Shape--polygonal
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? Nucleus--Large, round ¢ral (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 tosinusoids 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 ofcuboidal epithelium (cholangiocytes).
? Bile canal merge to form bile ductules
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? Bile ductules merge, enlarge, and form right andleft 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 bileand concentrate it by water re-absorption.
? Layers of gall bladder--
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a) Mucosab) Fibromuscular layer
c) Serosa/adventitia
? Mucosa--
? Lining epithelium simple columnar epithelium.
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? These cells have many small microvilli on theirapical 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 pancreaticjuice.
? 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 thegland 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 ofintercalated 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 Assessement1] 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) Lymphocytes4.]Hassall's corpuscles are present in
(a) Lymph node
(b) Spleen
(c) Thymus
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(d) Tonsil5.]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 lucidumd) 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 columnarc) Pseudostratified ciliated columnar
d) Stratified squamous non-keratinized
9.] Blood-air barrier is formed by all except ?
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a)Endothelium of capillaryb)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