Caption

Islet of Langerhans. Transmission Electron Micrograph (TEM) of a slice through a cell of the hormone-secreting islet of Langerhans in the mammalian pancreas. The dark round shapes in white spaces are membrane-bound secretory granules. These contain a densely granular core of hormone separated from the surrounding membrane by a clear space. The islets of Langerhans secrete hormones into the blood - mostly insulin and glucagon, which control blood sugar levels. Magnification x60,000 at 7x9 inch size.