Exocrine pancreas

Topic Completed: 1 August 2012

Minor changes: 5 March 2020

Copyright: (c) 2002-2020,, Inc.

PubMed Search: Exocrine pancreas[TI] free full text[sb]

Deepali Jain, M.D.
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Cite this page: Jain D. Exocrine pancreas. website. Accessed August 6th, 2020.
Definition / general
  • Acini comprise 80% of pancreas
  • Composed of columnar to pyramidal epithelial cells with minimal stroma
  • Basophilic due to prominent rough endoplasmic reticulum
  • Have well developed Golgi complex
  • Cells form apical oriented secretory complex with zymogen granules containing digestive enzymes (PAS+)
  • After stimulation, zymogen granules migrate to apical plasma membrane and release contents into lumen
  • Luminal border has prominent microvilli
  • Centroacinar cells: in center of acini, occasionally in clusters, with pale cytoplasm and oval nuclei
  • Intercalated duct: drains acini via intralobular ducts (cuboidal epithelium), to interlobular ducts lined by mucin secreting columnar cells
  • Pancreas produces 2 liters/day of bicarbonate rich fluid containing digestive enzymes and proenzymes, regulated by neural stimulation (vagus nerve) and humoral factors (secretin, cholecystokinin)
  • Pancreatic enzymes: trypsin, chymotrypsin, aminopeptidases, elastase, amylases, lipase, phospholipases, nucleases
  • Cholecystokinin: promotes discharge of digestive enzymes by acinar cells; released from duodenum in response to fatty acids, peptides and amino acids
  • Secretin: stimulates water and bicarbonate secretion by duct cells; is stimulated by acid from stomach and luminal fatty acids
  • Trypsin: catalyzes activation of the other enzymes
  • Pancreatic self digestion: prevented by - packaging of most proteins as inactive proenzymes, enzyme sequestration in zymogen granules, proenzymes activated only by trypsin which is activated only by duodenal enterokinase, trypsin inhibitors are present in ductal and acinar secretions, intrapancreatic release of trypsin activates enzymes which degrade other digestive enzymes before they can destroy pancreas, lysosomal hydrolases can degrade zymogen granules to prevent auto destruction if acinar secretion is impaired, acinar cells themselves are highly resistant to trypsin, chymotrypsin and phospholipase A2
Microscopic (histologic) images

Images hosted on other servers:

Acinar cells

Low power

Intercalary duct

Large excretory duct

Electron microscopy images


2 centroacinar cells with electron lucent cytoplasm

Ductular cells

Secondary interlobular duct

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