Insulin secretion in islets of Langerhans, pancreas

A photomicrograph of a section through a normal human pancreas, labelled for insulin. It shows the islets of Langerhans, which control insulin secretion, situated in a sea of exocrine tissue. The insulin is secreted by special groups of bells called beta cells. Insulin is involved in the regulation of sugar metabolism, being responsible for removing insulin from the blood by promoting glycogenesis and uptake of glucose by respiring cells.