Saliva is a liquid secreted by the salivary glands which is intended to moisten the mucosal membranes of the mouth and begin to digest foods.
Composition of saliva
Daily secretion of saliva varies depending on the individual from 500 to 1,200 millilitres and is a reflex action (through contact with food, and following a smell, or a memory). Its main component is water (99%), although saliva also contains ions (sodium, potassium, chloride, etc.) and organic components. It contains urea, glucose, hormones, RNA and many proteins, particularly digestive enzymes (amylase, lipase).
Function of saliva
The function of saliva is to moisturise and protect the buccal mucosal membranes and the teeth (by preventing caries and other infections). It also prepares food to pass into the oesophagus and into the digestive tract in general by wetting the food and beginning to digest it.
Saliva also protects teeth from caries. © David Shankbone, Wikimedia, CC by-sa 3.0