Pancreas: acini and islets !
- Organ
The pancreas is two glands in one: grape-like clusters make digestive enzymes, and scattered pale islands make insulin and glucagon.
Updated 2026-11-01
See it in 3D: Pancreas
What it is
Most of the pancreas is exocrine: serous acini whose cells store enzyme precursors in apical zymogen granules and release them into a branching duct system. Scattered among the acini are the islets of Langerhans, pale clusters of endocrine cells that release insulin, glucagon and somatostatin into the blood. Acinar enzymes explain pancreatitis; islet beta cells explain type 1 diabetes.
Structure
- Acinar cells: pyramidal, with basophilic base (rough endoplasmic reticulum) and eosinophilic apical zymogen granules.
- Centroacinar cells: pale cells inside the acinus, the start of the intercalated duct.
- Ducts: intercalated, intralobular and interlobular ducts, up to the main pancreatic duct; there are no striated ducts.
- Islets of Langerhans: pale, round clusters of endocrine cells with a rich capillary network.
Function
- Acinar cells secrete trypsinogen, chymotrypsinogen, lipase and amylase in response to cholecystokinin.
- Centroacinar and duct cells secrete bicarbonate-rich fluid in response to secretin.
- Trypsin is activated in the duodenum by enteropeptidase from enterocytes, protecting the gland.
Islet cells
| Cell | Hormone | Main action | Clinical |
|---|---|---|---|
| Beta | Insulin (and amylin) | Lowers blood glucose | Destroyed in type 1 diabetes; insulinoma |
| Alpha | Glucagon | Raises blood glucose | Glucagonoma (rash, diabetes) |
| Delta | Somatostatin | Inhibits other islet and gut hormones | Somatostatinoma |
| PP cell | Pancreatic polypeptide | Regulates exocrine secretion and appetite | Rare tumours |
Clinical notes
- Acute pancreatitis: enzymes activated inside the gland digest it; fat necrosis binds calcium (chalky white spots).
- Type 1 diabetes: lymphocytes infiltrate islets (insulitis) and destroy beta cells.
- Cystic fibrosis: thick secretions block the ducts and the exocrine tissue atrophies.
- Pancreatic ductal adenocarcinoma arises from duct epithelium, mostly in the head.
Test yourself
Think of the answer, then tap the question to see it.
Which cell type is found inside pancreatic acini but not in salivary acini?
The centroacinar cell, the first cell of the intercalated duct, which secretes bicarbonate.
How can pancreas be told apart from parotid on a slide?
Pancreas has islets and centroacinar cells and lacks striated ducts; parotid has prominent striated ducts and no islets.
Which islet cell is destroyed in type 1 diabetes?
The beta cell, which secretes insulin.
Which hormone stimulates bicarbonate secretion by pancreatic ducts?
Secretin, released by duodenal S cells when acid enters the duodenum.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Salivary glands: serous and mucous acini
- Liver: lobule, acinus, hepatocytes, sinusoids, Kupffer cells
- Enteroendocrine cells and GALT
Related conditions
Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.
Sources: 23.6 Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder - Anatomy and Physiology 2e | OpenStax (OpenStax (Rice University), 2022); Accessory Organs | SEER Training (National Cancer Institute (SEER Training), 2026).
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Representative model, for educational purposes only.