Pancreatic secretory cells. Coloured scanning electron micrograph (SEM) of a freeze-fracture through a healthy pancreas, showing the secretory tissue. This is part of the exocrine pancreas, whose cells (brown) secrete an enzyme-rich fluid into the small intestine, through the pancreatic duct. The enzymes in the fluid are secreted by zymogenic granules (red) in the cells. The enzymes are activated when they enter the small intestine, where they degrade the proteins, lipids, carbohydrates and nucleic acids in ingested food. The nuclei (yellow/green) of the cells are also seen. Magnification unknown.