Digestive System: Part 3

Liver

• hepatocytes - liver cells that are polygonal in shape
• produces most of the body's circulating plasma proteins such as albumins, lipoproteins, glycoproteins, prothrombin and fibrinogen, and nonimmune alfa and beta globulins.
  • structural components of the liver are:
    • parenchyma - consisting of organized plates of hepatocytes
    • connective tissue stroma - continuous with the fibrous capsule of Glisson
    • sinusoidal capillaries - vascular channels between the plates of hepatocytes
    • perisinusoidal spaces - lie between the sinusoidal endothelium and the hepatocytes
  • the classic lobule is a roughly hexagonal mass of tissue
    • contains the portal triad or canal which consists of the central vein, hepatic artery and bile duct
  • the portal lobule emphasizes the exocrine functions of the liver

Gallbladder

• mucosa of the gallbladder has several characteristic features
  • numerous deep mucosal folds
  • mucosal surface is simple columnar epithelium
  • the tall epithelial cells (cholangiocytes) exhibit numerous but short and not well developed apical microvilli
• lamina propria of the mucosa is rich in fenestrated capillaries and small venules but no lymphatic vessels
• muscularis externa has numerous collagen and elastic fibers among the bundles of smooth muscle cells

Exocrine Pancreas

• a serous gland
• secretory units are acinar or tubuloacinar in shape and are formed by a simple epithelium of pyramidal serous cells
• the centroacinar cells are the beginning of the duct system which have a centrally, flattened nucleus and attenuated cytoplasm, type of a squamous cell
• intercalated ducts are short and drain into intralobular collecting ducts
• no striated ducts