Saliva is the alkaline liquid secreted by the salivary glands and the mucous membrane of the mouth. Its principal constituents are water, mucus, buffers, enzymes (e.g., amylase) and some gamma globulins. The various salivary glands – parotid, submandibular, and sublingual – secrete slightly different types of saliva, varying in mucus and enzyme content.
The functions of saliva are to keep the mouth moist, to aid swallowing of food, to minimize changes of acidity in the mouth, and to digest starch. It is secreted in response to food in the mouth or by conditioned reflexes such as the smell or sight of food. Secretion is stimulated by both the sympathetic and the parasympathetic nervous system. A small but regular flow of saliva is maintained to promote cleanliness in the mouth even when food is not being eaten.