Pancreatic islets

Insulae pancreaticae (Langerhans)

Endocrine & glandsGlandsAbdomen

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What it is

The islets of Langerhans: roughly a million microscopic clusters of hormone cells scattered through the pancreas, shown here as 42 exaggerated markers running from the head to the tail (where they are most numerous). They make up only 1–2 % of the organ, the rest being digestive-enzyme tissue.

Function

Beta cells secrete insulin (lowers blood glucose), alpha cells glucagon (raises it), delta cells somatostatin and PP cells pancreatic polypeptide.

Size

Each islet 0.1–0.2 mm across (markers here are ~2.5 mm); about 1–1.5 g of islet tissue in total

Clinical note

Type 1 diabetes is autoimmune destruction of the beta cells; the islets are transplanted into the liver's portal vein in islet-cell transplantation.