Saliva is a watery substance formed in the oral cavity, secreted by the salivary glands. It consists primarily of water accounting for 99%; inorganic ions, secretory proteins and other substances account for 1% or less. It also include antibodies, blood clotting factors, amino acids, urea, uric acid and hormones.
The total volume of saliva secreted by humans is approximately 1000 to 2000 ml daily. During sleep, the amount of saliva secreted drops to nearly zero. More saliva produced when you eat.
Saliva moistens food and helps it breakdown into smaller particles to initiate digestion. The moistening and lubricating properties of saliva allow the formation of bolus and facilitate the process of swallowing. It also helps in taste perception, speech, digestion and protection of the oral cavity.