Pancreatic acinar cells, coloured transmission electron micrograph (TEM). Acinar cells (exocrine pancreatic cells) produce and secrete digestive enzymes to the small intestine, via the pancreatic ducts. The enzymes are excreted in vesicles known as zymogen granules (round). The enzymes are produced, packaged and secreted by each cell's endoplasmic reticulum and golgi apparatus (strands). Some of the cell nuclei are also visible (orange). The cells are grouped in a cluster called an acinus that encloses a central duct (white, centre) into which the enzymes are secreted.