Histology Pre-Lab. # 11 6/4/2016 LIVER/ GALL BLADDER & PANCREAS BY PROF. DR.ANSARI MBBS SEMESTER I 1

Objectives To learn the histology of liver, classical lobule, portal triad and hepatic acinus. To distinguish gall bladder from other tissues. To understand the microscopic structure of pancreas. To learn the histology of liver, classical lobule, portal triad and hepatic acinus. To distinguish gall bladder from other tissues. To understand the microscopic structure of pancreas. 6/4/20162

Liver is the largest gland of our body Hepatocytes are arranged in hepatic cords/palisades/sheets around a central vein. Glisson’s capsule is the connective tissue covering of liver, it sends septa in the liver substance, which divides in to classical lobule/portal lobule and hepatic acinus. Classical hepatic lobule is a six cornered structure, at each corner there is a portal triad. Hepatocytes are arranged in hepatic cords/palisades/sheets around a central vein. Glisson’s capsule is the connective tissue covering of liver, it sends septa in the liver substance, which divides in to classical lobule/portal lobule and hepatic acinus. Classical hepatic lobule is a six cornered structure, at each corner there is a portal triad. 6/4/20163

Classical lobule Hepatocytes radiate from central vein and spreads peripherally. Between the adjacent rows of hepatocytes there are venous sinusoids lined by Kupffer cells. Hexagonal outlines are cornered by portal triads. 6/4/20164

Portal triad At each corner of classical hepatic lobule there is a portal triad having a radicle of portal vein, a radicle of hepatic artery and a bile duct. Lymphatics and nerve plexus are also present at portal triad. 6/4/20165

Space of Disse The space between the fenestrated endothelium and the cords is named the space of Disse.fenestrated endotheliumcords The location for the space of Disse is the perisinusoidal space, this space contains scattered reticular (collagen) fibers and fibroblasts. The Ito cells (fat-storing cells) are located in the Space of Disse. They store Vitamin A and synthesize hepatic growth factor. Microvilli of hepatocytes are also content of space of Disse. 6/4/20166

Ito cell in space of Disse stores Vitamin “A” in fat droplets 6/4/20167 Hepatocyte Sinusoid Electron Microscopic picture

Kupffer cells Kupffer cells are macrophages found in the sinusoids of the liver.sinusoids liver Kupffer cells clean bacteria out of the portal blood stream and also removing worn- out red blood cells and recycling hemoglobin. 6/4/20168

Space of Mall The space between the limiting lamina and the connective tissue of the portal canal is a tissue space called the space of Mall. Lymph from the space of Disse seeps into this space and then into lymph vessels in the portal canal 6/4/20169

Hepatic acinus Hepatic acinus / liver acinus is a mass of liver parenchyma that is supplied by terminal branches of the portal vein and hepatic artery and drained by a terminal branch of the bile duct. It is a diamond shaped structure, central veins and portal triads are at the periphery of the diamond. Hepatic acinus / liver acinus is a mass of liver parenchyma that is supplied by terminal branches of the portal vein and hepatic artery and drained by a terminal branch of the bile duct. It is a diamond shaped structure, central veins and portal triads are at the periphery of the diamond. 6/4/201610

6/4/ Portal lobule is a triangular area of liver parenchyma. The corners of triangle are having central veins of adjacent liver tissue. Classical lobule hexagonal

Gall bladder has mucosa, Muscularis externa and adventitia 6/4/201612

Pancreas 6/4/ Endocrine part has islets of Langerhans Exocrine part has Serous acini & centroacinar cells

Centroacinar cells The centre of each acinus is lined by small centroacinar cell. These cells form the first part of intercalated ducts. The pancreatic acini are serous acini, with eosinophilic granules apically and round centrally situated nuclei. 6/4/201614

Acinar cells & centroacinar cell 6/4/201615

Islets of Langerhans The islets are composed of three cell types: alpha cells, beta cells, and delta cells. These cells cannot be readily distinguished without special stains. Alpha cells (15-20%) are found at the periphery and secrete glucagon. Beta cells (70%) are found more centrally and secrete insulin. Delta cells (5-10%) are found throughout the islet and secrete somatostatin. 6/4/201616

Applied anatomy Cholelithiasis is formation of gall stones in the biliary system. Jaundice is yellowish discoloration of skin/mucus membrane, due to accumulation of bile salts in the circulation. Diabetes mellitus is due to poor secretion of beta cells(Insulin) of islets of Langerhans. 6/4/201617