Topic Completed: 1 August 2012

Minor changes: 22 October 2020

Copyright: 2002-2020,, Inc.

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

Deepali Jain, M.D.
Page views in 2020 to date: 344
Cite this page: Jain D. Histology. website. Accessed November 23rd, 2020.
Endocrine pancreas
  • Consists of islets of Langerhans, represents 1% of pancreas (percentage higher at birth)
  • Round, compact, highly vascularized with scanty connective tissue
  • More irregular outline and trabecular arrangement in posterior head of pancreas with cells producing pancreatic polypeptide
  • Size of islets usually 0.1 to 0.2 mm, endodermal origin, one million islets present in pancreas
  • Islet composition: beta cells (68%), alpha cells (20%), delta cells (10%), PP cells (2%), serotonin cells (rare)
  • Postgastrectomy, may get islet hypertrophy, then beta cell proliferation, then atrophy and amylin deposits (Hum Pathol 2000;31:1368)
  • Alpha cells: produce glucagon; peripherally dense and round on EM
  • Beta cells: produce insulin and islet cell amyloid polypeptide (amylin), crystalline appearance on EM with surrounding halo
  • Delta cells: produce somatostatin (represses release of insulin and glucagon), large pale granules on EM
  • D1 cells: produce vasoactive intestinal polypeptide (VIP), which induces glycogenolysis and hyperglycemia, stimulates GI fluid secretion and causes secretory diarrhea
  • Enterochromaffin cells: synthesize serotonin, produce carcinoid syndrome
  • Gastrin cells: pancreas usually lacks gastrin producing cells, although gastrinomas are common
  • PP cells: produce pancreatic polypeptide, which stimulates secretion of gastric and intestinal enzymes and inhibits intestinal motility; present in islets and scattered in exocrine pancreas; more PP cells in posterior head of pancreas (from ventral bud)
  • Nesidioblastosis: islets in intimate association with ducts with formation of ductuloinsular complexes
  • Nesidiodysplasia: loss of the usual centrilobular concentration of larger islets, with increased small irregularly distributed aggregates of islet cells; also increase in beta cell nuclear size and DNA content; may be associated with endocrine neoplasms (Hum Pathol 1988;19:1215)
  • Peliosis: selective congestion and dilation of vessels of islets only, not seen in vessels elsewhere
Exocrine pancreas
  • Acini comprise 80% of pancreas
  • Composed of columnar to pyramidal epithelial cells with minimal stroma
  • Basophilic due to prominent rough endoplasmic reticulum
  • 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

AFIP images

Islets in newborn

Adult pancreas - ordinary type islet

Adult pancreas - irregular type islet

Adult pancreas: distribution of islet cell types

Islet rich in PP cells in posterior part of pancreatic head

Islets: cells with clear cytoplasm

Clustering of irregular islets

Contributed by Cesare Bordi, M.D.

Islet hyperplasia of

Electron microscopy images

AFIP images

Adult pancreatic islet cells

2 centroacinar cells with electron lucent cytoplasm

Images hosted on other servers:

Zymogen granules

Back to top
Image 01 Image 02