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Acini
Acinus
Exocrine secretory unit of the pancreas
  • Acinar region = site of secretion, secrete digestive enzymes
  • Duct region = modify initial secretion, secrete bicarbonate.
Digestive enzymes and bicarbonate merge to form pancreatic juice.
  • Both neural and hormonal stimuli regulate pancreatic juice secretion for its subsequent release and action in the duodenum.
  • Hormonal regulation occurs via: secretin and cholecysotkinin (CCK).
CCK
  • Triglycerides, fatty acids, and amino acids triggers CCK release from the duodenum.
  • CCK triggers acinar section of pancreatic acinar digestive enzymes.
(Digestive enzymes include pancreatic amylase, pancreatic lipases, nucleases, and proteases.)
Secretin
  • Acidic chyme triggers secretin release from the duodenum.
  • Acts on pancreatic ductal cells, which triggers bicarbonate release.
Potentiation
  • Amplification of one hormone's effects by another hormone, which generates a larger signal than if either hormone acted alone.
  • CCK and secretin act together via potentiation to amplify each other's signal.
(Pancreatic duct cells can also by stimulated by CCK, while acinar cells similarly respond to secretin stimulation)
  • CCK and secretin stimulation of both ductal and acinar cells promotes additional bicarbonate & digestive enzyme secretion, respectively.
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Acini

pancreas
– Secretes pancreatic juice that aids digestion
– Secretes hormones involved in metabolism.
Pancreatic secretions
Two major components:
  • Digestive enzymes
– Acts on fats, carbohydrates, proteins, and lipids.
  • Bicarbonate
– Neutralizes acidic chyme in the duodenum.

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