Lec 32- Gallbladder and pancreas

• The gallbladder is a blind-ended pouch with a neck and fundic region. It's function is to store and concentrate bile
• Bile that leaves the liver is dilute and is concentrated in the gallbladder. In the gallbladder, it resorbs 90% of water from bile to concentrate it.
• The role of the pancreas is to create digestive enzymes and bicarbonate rich fluid
• How does the bile from the liver enter the cystic duct to the gallbladder?

  When the sphincters to the hepatopancreatic ampulla are closed bile backs up and bile will take the path of least resistance to the gallbladder.
• The gallbladder contains irregular folds but does not have villi. No muscularis mucosae, no submucosa, but does have a muscularis externa but is very disorganized.
• The epithelium of the gallbladder is simple columnar epithelium with microvilli
• The following slide is of the gallbladder

  
• Gallbladder epithelium has very well developed tight junctions on their lateral surface. On their lateral surfaces, these cells have Na+/K+ ATPase pumps. These cells also have big aquaporins for the passage of water. When the solutes (Na+/K+) are pumped out, the water will follow via osmotic pressures and be returned to the circulatory system

  
• The pancreas is a large compound acinar gland. The acinar cells secrete zymogen granules of digestive enzymes into the pancreatic duct which meets with the common bile duct to the hepatopancreatic ampulla. The duct cells secrete bicarbonate-rich fluid to neutralize the stomach acid coming into the duodenum
• Label the following sections of this slide

  A) serous secreting acini

  B) pancreatic islets

  
• The serous acini of the pancreas is the exocrine portion and the pancreatic islets are the endocrine portion
• The pancreas only contains intercalated ducts
• The pancreatic serous acini can be differentiated from the parotid serous acini due to the presence of centroacinar cells and the absence of striated ducts
• Label the following slide

  A) acinar cell

  B) centroacinar cell

  C) intercalated duct

  D) zymogen granules

  
• The digestive enzymes produced in the pancreas by acinar cells are

  • trypsinogen
  • amylase
  • lipase
• Digestive enzymes secreted by acinar cells in the liver are secreted as proenzymes and later are cleaved to be activated in the duodenum. Trypsinogen gets cleaved by membrane bound enterokinase (on the glycocalyx of enterocytes) to trypsin which will cleave and activates the other enzymes
• When you eat a meal, enteroendocrine cells will release secretin and cholecytokinin into the bloodstream through their basal surface. From there, they will act on different accessory organs to stimulate digestion.
• Cholecystokinin acts on the gallbladder to cause it to contract and push bile towards to duodenum to emulsify fats. It will also act on the pancreatic acini to dump their zymogen granules into ducts to lead to digesiton
• Secretin acts on the ducts of the pancreas to stimulate the release of bicarbonate
• Which histological characteristic is prominent in the duct system of the pancreas?

  simple cuboidal epithelium