Saliva is the biological fluid of the mouth secreted by the salivary glands. Saliva has two main roles: to moisten the mucous membranes of the mouth through the production of saliva or salivation and to begin the digestion of food through insalivation, which corresponds to the impregnation of food by saliva as it passes through the mouth and is chewed. The first function of humification allows us to speak with ease and to chew without injury. For its role in digestion, saliva contains enzymes and amylases. In addition, saliva neutralises the acid produced by dental plaque thanks to the bicarbonates, phosphates and urea that it contains, which is known as its buffering capacity. Saliva also has, to a certain extent and against certain organisms or viruses, disinfectant properties.

Primary saliva is formed in the acinar cells and has the same composition as plasma. It is then modified in the excretory canal to form secondary saliva. During the passage through the duct, the duct cells actively secrete K+ and HCO3- and actively absorb Na+ and Cl-. Its efficiency depends on the salivary glands, but also on the pancreas.