Pancreas. Light micrograph of a cross section through an islet of Langerhans in the pancreas. The islet (centre, pale pink) is composed of clumps of secretory cells. The main secretions from these cells are the hormones glucagon and insulin that control blood sugar. These cells are endocrine, their secretions go straight into the bloodstream. The cells surrounding the islet are packed into secretory acini (dark pink) which secrete digestive enzymes. This is the exocrine pancreas as the enzymes pass out into the gut via ducts. A duct can be seen above the islet (centre left to upper centre). Haematoxylin and eosin stained. Magnification x65 at 35mm size.