The islets of Langerhans are small groups of cells in the pancreas that function as an endocrine gland. The alpha (or A) cells secrete the hormone glucagon, the beta (or B) cells secrete insulin, the delta (or D) cells secrete somatostatin, and the pancreatic polypeptide (PP) cells secrete pancreatic polypeptide.

 

The islets of Langerhans are named after their discoverer, the German anatomist and microscopist Paul Langerhans (1847–1888).