LIVER GALL BLADDER PANCREAS LIVER PIGS LIVER LOBULES

LIVER, GALL BLADDER, PANCREAS

LIVER

PIG’S LIVER LOBULES

HUMAN LIVER LOBULES

PORTAL AREA (PORTAL TRIAD)

PORTAL AREA (PORTAL TRIAD) Bile Duct Xx. XXXXXXX

LIVER 1 - Stroma: a- Capsule: Glisson’s Capsule. b- Septa (absent in human) & Portal areas (Portal triads) (Portal tracts) (Portal spaces) (Portal canals) c- Network of reticular fibers. 2 - Liver lobules ( classic hepatic lobules )

CLASSICAL LIVER LOBULE (classical hepatic lobule) It is formed of a polygonal mass of tissue , With portal areas at the periphery & Central (centrolobular) vein in the center.

Borders of the classical liver lobule 1 - Septa: C. T. septa (e. g. in pigs). Portal areas (Portal triads): 2 Are located in the corners of the lobules (usually 3 in No. ). Contents of portal area: a- C. T. b- Bile ducts ( interlobular bile ducts ). c- Venule ( Branch of portal vein). d- Arteriole ( Branch of hepatic artery). e- Lymphatics. f- Nerves.

CONTENTS OF THE CALSSICAL LIVER LOBULE 1 - Anastomosing plates of hepatocytes. 2 - Liver sinusoids (hepatic blood sinusoids): In between the plates. 3 - Spaces of Disse (perisinusoidal spaces of Disse). 4 - Central vein ( Terminal hepatic venule ). 5 - Bile canaliculi. 6 - Limiting plate of hepatocytes & space of Moll.

HEPATOCYTES (L/M)

HEPATOCYTES (L/M) *Are grouped in interconnected plates. *Liver sinusoids are located in the spaces between these plates. *Are polyhedral in shape. *Nucleus: 1 or 2, vesicular, 1 or 2 nucleoli, May be polyploid nucleus. *Cytoplasm: acidophilic? Mitochondria ++++, s. ER. With basophilic bodies? r. ER. Glycogen. *Limiting plates & space of Moll.

HEPATOCYTE ( E/M ) (Fascia Type) (Not mentioned in Gartner)

HEPATOCYTE ( E/M )

HEPATOCYTES (E/M) • Surfaces (Plsmalemma has two domains 1 & 2): 1 - Sinusoidal domains (surfaces): lines space of Disse, contains many microvilli. 2 - Lateral (Intercellular) Domains (surfaces). (3) Canalicular surface: ? ? ? part of lateral (intercellular) surface with bile canaliculus.

HEPATOCYTES (E/M) • Junctions: 1 - Junctional complexes: Tight Junction (Fasciae occludentes), adherent Junction (? ? ? )& Desmosome(? ? ? ? ). 2 - Gap junctions.

HEPATOCYTES (E/M) Organelles: 1 - Mitochondria: ++++ 2 - ER (s. ER & r. ER): abundant. 3 - Golgi complex. 4 - Lysosomes. 5 - Peroxisomes. Inclusions (Deposits): 1 - Glycogen 2 - Lipid 3 - Lipofuscin (old age)

LIVER SINUSOIDS & SPACE OF DISSE

FENESTRATED ENDOTHELIUM

LIVER SINUSOIDS (1) ENDOTHELIAL CELLS: Fenestrated (sieve plates: are clusters of fenestrae) & discontinuous → Free passage of plasma. Basal lamina is absent. Supported by a delicate sheath of reticular fibers of space of Disse. (2) Kupffer cells: Are macrophages. Are stellate in shape. Are found on the luminal surface of the endothelial cells, within the sinusoids. Function: phagocytosis.

SPACE OF DISSE (PERISINUSOIDAL SPACE) Contents: 1 - Fat-storing cells (hepatic stellate cells) ( Ito cells): contain vitamin A-rich lipid. form reticulin. 2 - Reticular fibers (type III collagen). 3 - Plasma of blood. 4 - Microvilli of hepatocytes. 5 - Pit cells: may be natural killer cells.

BILE CANALICULI

Bile canaliculus

BILE CANALICULUS • The 1 st. Portion of bile duct system. • It is limited only by the cell membranes of 2 hepatocytes. • It has few microvilli in its interior. • The cell membranes of the 2 hepatocytes near the canaliculus are joined by tight junctions (fasciae occludentes).

BILIARY PASSAGES 1 - Bile canaliculi. 2 - Cholangioles: are lined with hepatocytes, low cuboidal cells & occasional oval cells. 2 - Canals of Hering: Are parallel to inlet arterioles & inlet venules. Are lined with low cuboidal cells with some ovoid cells. 3 - Interlobular Bile ducts: * in the portal areas * simple cuboidal (or simple columnar? ? ? ? ). 4 - Right & left Hepatic ducts.

BLOOD SUPPLY (A) Portal vein system: 1 - Portal venules: in portal areas. 2 - Distributing veins (perilobular venule): at the periphery of the lobule. 3 - Inlet venules. 4 - Sinusoids. 5 - Central vein. 6 - Sublobular vein. 7 - Collecting veins. 8 - Two hepatic veins. (B) Arterial system: 1 - Interlobular arteries ( hepatic arterioles of portal areas ). 2 - Distributing arteries (or arterioles). 3 - Inlet arterioles. 4 - Sinusoids.

THE 3 CONCEPTS OF LIVER LOBULES • 1 - Classical hepatic lobule • 2 - Portal lobule • 3 - Hepatic acinus (acinus of Rappaport)

PIG’S LIVER LOBULES

LIVER ACINUS

LIVER REGENERATION It is due to: 1 - Replicative capability of hepatocytes. 2 - In severe hepatotoxicty: Mitotic activity of the oval cells in the wall of cholangioles and canals of Hering. N. B. Many of regeneration factors are released by Ito cells in the space of Disse.

GALL BLADDER

GALL BLADDER (1)Mucosa: has abundant folds: 1 - Simple columnar epithelium: a- clear cells++++ b- brush cells. contain few mucinogen granules. 2 - Lamina propria: vascularized Loose C. T. N. B. Tubuloacinar mucous glands in the neck of G. B. → secrete most of the mucus present in the bile. (2) Muscle layer: SMF( Mostly oblique, others are longit. ) (3) Serosal adventitia.

PANCREAS

EXOCRINE PORTION Of Pancreas (A)Stroma: capsule, septa & reticular fibers. (B) Pancreatic acini: Acini with centroacinar cells. No myoepithelial cells. (C) Duct system: Centroacinar cells, intercalated ducts (low cuboidal), intralobular ducts (are NOT prominent ), interlobular N. B. No striated ducts

PANCREAS

Pancreatic acinus & Centroacinar cells

PANCREAS

ISLETS OF LANGERHANS L/M: 1 - fine capsule of reticular fibers. 2 - cords of polygonal or rounded cells separated by a network of blood capillaries.

Cells of islets of Langerhans 1 - Alpha (α) cells: 20%, glucagon. 2 - Beta (ß) cells: 70%, insulin. 3 - Delta cells: 5%, somatostatin. 4 - PP cells (F cells): 1%, pancreatic polypeptide. 5 - G cells: 1%, Gastrin.

PANCREAS

ISLET OF LANGERHANS

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