Pancreas. Light micrograph of a cross section through an islet of Langerhans in the pancreas. The islet (pale pink, centre) 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 pancreas also acts as an exocrine gland, releasing digestive enzymes into the duodenum, which leads to the small intestine. Magnification: x130 at 6x6cm size.