Normal salivary gland. Coloured scanning electron micrograph (SEM) of a section through a healthy parotid gland, showing serous cells (large), which produce proteins and enzymes. At upper right is a duct where saliva is drained out. The parotid glands are the largest of the salivary glands. They produce enzymes and proteins and facilitate mastication and swallowing and to begin the digestion of starches. Magnification: x1250, when printed 15 centimetres wide.