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Pancreatic Islets
Gray's Anatomy (1918) plate, public domain
The pancreatic islets (of Langerhans) are the endocrine islands scattered through the pancreas — 1-2 million clusters making up a small fraction of the gland. Their beta cells make insulin, alpha cells make glucagon, and delta cells make somatostatin; together they hold blood glucose in a narrow range. Insulin lowers glucose by driving it into cells and storage; glucagon raises it by releasing glucose from the liver.
Key facts
- Beta cells sense glucose directly and release insulin within minutes of a meal.
- Islet blood flow is disproportionately rich, so hormones reach the circulation quickly.
- Insulin and glucagon act as a paired thermostat, each restraining the other through local signalling.
- The islets' nerve supply fine-tunes secretion in anticipation of food — the cephalic phase.
What can go wrong
In type 1 diabetes the immune system destroys beta cells, causing absolute insulin deficiency. In type 2 diabetes the body resists insulin and beta cells gradually fail to keep up, so glucose rises. Rare islet tumours overproduce hormones — insulinomas cause hypoglycaemia attacks, glucagonomas a distinctive rash and diabetes. Islet and pancreas transplantation are specialised options in some diabetes care.
Related conditions
Related procedures & tests
Related symptoms
Frequently asked questions
How much of the pancreas is endocrine?
Only about 1-2% by volume — yet that small fraction controls the fuel supply for the entire body, which is why islet failure has such wide effects.
What is the difference between type 1 and type 2 diabetes at the islet?
In type 1 the beta cells are destroyed by autoimmunity, so insulin is absent; in type 2 the cells survive but cannot overcome the body's insulin resistance.
Educational information only. This atlas explains normal anatomy and describes conditions in general terms; it is not medical advice and does not replace assessment by a qualified clinician. If you have symptoms that worry you, seek medical care.
