Liver and Pancreas Histology

Study Notes

Liver and Pancreas Histology

The liver is a solid organ composed of tightly packed, pink-staining hepatocyte plates.
The outer surface of the liver is covered by a collagenous tissue called Glisson's capsule.
Glisson's capsule has a layer of mesothelial cells from the peritoneum.
The liver's structural integrity is maintained by a delicate reticulin fiber meshwork continuous with Glisson's capsule.
The hepatic lobule is the structural unit of the liver.
Hepatic lobules are hexagonal and centered on a terminal hepatic venule (or central vein).
Portal tracts (portal triads) are positioned at the angles of the hepatic lobule.
Portal tracts contain a terminal branch of the hepatic portal vein, hepatic artery, and bile ductules.
Lymphatics are present in the portal tracts.
Bile ductules merge to form larger, centrally located trabecular ducts which drain into intrahepatic ducts, the right and left hepatic ducts, and the common hepatic duct, eventually reaching the duodenum via the common bile duct.
Hepatocytes are arranged in anastomosing plates or double-layered rows radiating from the central vein.
Hepatic sinusoids are lined by discontinuous fenestrated endothelium.
Kupffer cells, phagocytic cells, are scattered among the endothelial cells.
Hepatocytes are large, polyhedral cells with round nuclei with dispersed chromatin and prominent nucleoli.
Binucleate cells are common in normal liver tissue.
The limiting plate of hepatocytes borders the portal tract.
Blood from the portal vein and hepatic artery branches flows to the adjacent central veins.

Pancreas

The exocrine pancreas forms the bulk of the gland.
It secretes an enzyme-rich alkaline fluid into the duodenum via the pancreatic duct.
Pancreas is a lobulated gland covered by a thin collagenous capsule, extending as delicate septa between lobules.
Each pancreatic acinus is made up of irregularly shaped, pyramid-shaped secretory acinar cells.
The apices of acinar cells surround a central lumen.
The acinus drains into intercalated ducts.
Acinus contain two types of cells.
Acinar cells are pyramidal and protein-secreting with basally located nuclei, and eosinophilic secretory granules containing proenzymes.
Centroacinar cells are located in the centers of acini, with pale nuclei and sparse, pale-stained cytoplasm.
Intercalated ducts drain into intralobular ducts.
Intralobular ducts are lined by simple, low cuboidal epithelium that becomes stratified cuboidal in larger ducts.

Endocrine Pancreas

The endocrine pancreas is composed of islets of Langerhans scattered within the exocrine gland.
Islets vary in size and most numerous in the tail of the pancreas, are encapsulated in a fine collagenous network containing fenestrated capillaries.
Endocrine cells are small with pale, granular cytoplasm as opposed to the large cells of surrounding exocrine tissue.
The islets contain different cell types, each secreting specific polypeptide hormones.
Main secretory products: insulin (beta cells) and glucagon (alpha cells).
Somatostatin (delta cells) has diverse gastrointestinal effects.
Other peptide-producing cells include enterochromaffin (EC) cells.