What are the cells in the pancreas that secrete insulin?

The cells in the pancreas that secrete insulin are the beta cells of the islets of Langerhans.

The islets of Langerhans are small clusters of endocrine tissue scattered throughout the pancreas. Their beta cells release insulin when blood glucose rises, helping body cells absorb glucose and helping the liver store it as glycogen. The islets also contain alpha cells, which produce glucagon, and delta cells, which produce somatostatin.

German anatomist Paul Langerhans identified these clusters in 1869, although he did not initially know their hormonal role. The name “islets” refers to their island-like appearance among the pancreas’s enzyme-producing tissue. A common mix-up is to call the entire pancreas an insulin-secreting organ: most of it makes digestive enzymes, while insulin comes specifically from beta cells inside the islets.

In type 1 diabetes, the immune system destroys many insulin-producing beta cells. Type 2 diabetes usually begins with insulin resistance and may later involve reduced beta-cell function.