Exam 3 - Digestive Glands and Liver

Question 1

What is the general histological organization of the pancreas?

Answer 1

• Lobulated, compund, tubulo-alveolar gand with both an exocrine and an endocrine secretory function
• Connective tissue Support
  
  • no organized capsule
  • Thin layer of loose CT form which septa pass internally dividing the gland into many small lobules
  • the delicate CT contains blood vessels, lymphatics, nerves, and excretory ducts

Question 2

What are the ducts and their secretion

Answer 2

• Ducts of wirsun os te maon excretory duct
• duct of santorini is the smaller acessory duct
• interlobular duct
  
  • lined with simple columnar epithelium and goblet cells
• intercalated ducts
  
  • lined with low cubodial cells
  • cells with receptors for secretin
  • cells secerete water and bicarbonate

Question 3

What is the histology of the pancreatic acinus and know function of acinar, centro acinar, and ductal epithelial cells

Answer 3

• Acini are serous
• Acinar cells are pyramidal serous cells
  
  • basal zone is basophillic and contains nucleus and RER
  • Apical zone with zymogen granules
    
    • precursors of enzymes in pancreatic juice
    • trypsin, chymotrypsin, amylase, and lipase
    • specific receptors for cholecystokinin
• Centroacinar cells
  
  • Form truncated cubodial epithelium within the lumen of acini continous with the eputhelium of intercalated duct
  • unique to pancreas
  • no striated ducts
  • no myepithelial cells
  • release of digestive enzymes from serous acinar cells is stimulated by CCK
  • Bicarbonate rich, alkaline fluid is released by ductal epithelial cells in response to secretin

Question 4

What is the action of secretin and CCK on pancreatic acini

Answer 4

• secretion of bicarbonate ions is regulated by secretin:
  
  • secreted by duodenal enteroendocrine cells wen stimulated by food entering small intestine
• Synthesis of bi carbonate ions
  
  • Carbon dioxide diffusees into intercalated ducts from blood.
  • CO₂ + H₂O -> H₂CO₃ (requires carbonic anhydrase)
  • H₂CO₃ -> HCO₃^- + H⁺
  • HCO₃^- is actively transported to lumen of intercalated duct
  • Na⁺ and H⁺ are exchanged with Na+ flowing into ducct lumen and H⁺ flowing into blood
• Release of digestive enzymes by serous acinar cells is stimulated by CCK

Question 5

What is the synthetic pathway of pancreatic bicarbonate ions?

Answer 5

Carbon dioxide diffusees into intercalated ducts from blood.

CO2 + H2O -> H2CO3 (requires carbonic anhydrase)

H2CO3 -> HCO3- + H+

HCO3- is actively transported to lumen of intercalated duct

Na+ and H+ are exchanged with Na+ flowing into ducct lumen and H+ flowing into blood

Question 6

What are islets of langerhans?

Answer 6

• These are endodermal derived cell aggregations which are interspersed irregularly among the acini
• cell types
  
  • A cells (alpha cells)
    
    • have fine cytoplasmic granules and are presumed to form glucagon
  • B cells (beta )
    
    • Have coarse cytoplasmic granules; they are more numerous than alpha cells and produce insulin
  • D cells (delta)
    
    • secrete somatostatin which helps to control levels of insulin and glucagon