Caption

Islet of Langerhans. Light micrograph of a section through an islet of Langerhans in the pancreas. The islet (centre right) is composed of clumps of secretory cells. The main secretions from these cells are the hormones glucagon and insulin, which control blood sugar. These cells are endocrine, their secretions go straight into the bloodstream. The cells surrounding the islet are packed into secretory acini (pink) which secrete digestive enzymes. This part of the pancreas is exocrine, as the enzymes pass straight out into the gut, via ducts. Magnification: x195 when printed 10 centimetres wide.