[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Histology](https://durgical.com/en/histology/) › [Digestive system](https://durgical.com/en/histology/#a-digestive) › Pancreas: acini and islets

[Histology](https://durgical.com/en/histology/) · [Digestive system](https://durgical.com/en/histology/#a-digestive)

# 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](https://durgical.com/en/anatomy/pancreas/)

## Key points

- Exocrine acini (most of the gland) + endocrine islets (a small fraction).
- Centroacinar cells are unique to the pancreas.
- No striated ducts: distinguishes pancreas from parotid on a slide.
- Beta cells are the most numerous islet cells; destroyed in type 1 diabetes.
- Cholecystokinin drives enzymes; secretin drives bicarbonate.

## 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](https://durgical.com/en/conditions/type-1-diabetes-mellitus/) | 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.

## Memory aid

In the pancreas the acini are the kitchen and the islets are the thermostat.

## 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.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/histology/pancreas-acini-and-islets/)

## See it in 3D

The structures of Durgical's 3D anatomy where it is found.

- [Pancreas](https://durgical.com/en/anatomy/pancreas/)

## Related

- [Salivary glands: serous and mucous acini](https://durgical.com/en/histology/salivary-glands-serous-and-mucous-acini/)
- [Liver: lobule, acinus, hepatocytes, sinusoids, Kupffer cells](https://durgical.com/en/histology/liver-lobule-acinus-hepatocytes-sinusoids-kupffer-cells/)
- [Enteroendocrine cells and GALT](https://durgical.com/en/histology/enteroendocrine-cells-and-galt/)

## Related conditions

- [Acute pancreatitis](https://durgical.com/en/conditions/acute-pancreatitis/)
- [Type 1 diabetes mellitus](https://durgical.com/en/conditions/type-1-diabetes-mellitus/)
- [Pancreatic cancer](https://durgical.com/en/conditions/pancreatic-cancer/)

[← All of histology](https://durgical.com/en/histology/)

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](https://openstax.org/books/anatomy-and-physiology-2e/pages/23-6-accessory-organs-in-digestion-the-liver-pancreas-and-gallbladder) (OpenStax (Rice University), 2022); [Accessory Organs | SEER Training](https://training.seer.cancer.gov/anatomy/digestive/regions/accessory.html) (National Cancer Institute (SEER Training), 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/histology/pancreas-acini-and-islets/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/histology/pancreas-acini-and-islets/