Pancreatic islets

The pancreas contains tissue with an endocrine and exocrine role, and this division is also visible when the pancreas is viewed under a microscope.

The tissues with an endocrine role can be seen under staining as lightly-stained clusters of cells, called pancreatic islets (islets of Langerhans).

Darker-staining cells form clusters called acini, which are arranged in lobes separated by a thin fibrous barrier. The secretory cells of each acinus surround a small intercalated duct. Because of their secretory function, these cells have many small granules of zymogens that are visible. The intercalated ducts drains into larger ducts within the lobule, and finallyinterlobular ducts. The ducts are lined by a single layer of columnar cells. With increasing diameter, several layers of columnar cells may be seen.