Contents of saliva include 98% water along with electrolytes, mucus, white blood cells, epithelial cells, enzymes and antimicrobial agents. Saliva has various functions in the body. Saliva is produced by the salivary glands situated on the sides and under the tongue.
Saliva secretion is triggered by intake of food. Sometimes, just the thought of favorite foods can trigger saliva production.
Composition of Saliva:
About 98 to 99% of saliva is made up of water. Other components of saliva are as given below.
- Electrolytes including sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate and iodine.
- Mucus that lines the mouth cavity
- Antibacterial compounds like hydrogen peroxide, immunoglobulin-A
- Antimicrobial enzymes like lysozyme, lactoferrin, etc
- Epidermal growth factor
- Enzymes like alpha-amylase, lingual lipase, kallikrein, etc
- Minor enzymes like glutathione transferase, aldehyd dehydrogenase, etc
- Proline-rich proteins for the function of enamel formation, Calcium ion binding
- Bacterial cells and products
- Opiorphin, a pain-killing substace
- Haptocorrin – the protein that binds to vitamin-B12 so that it does not get disintegrated in the stomach
Functions of Saliva:
Saliva helps in digestion of food and maintaining the health of mouth cavity. The various functions are as follows.
- Lubrication is one of the functions of saliva as it lines the oral cavity. This makes the food easy to chew and swallow. It also protects the mouth from trauma while speaking. When there is reduced saliva secretion, mouth sores are formed and food tends to stick to the inside of the mouth.
- Digestion process starts as soon as the food particles come in contact with the saliva in the mouth.
- Saliva helps in moistening the food so that it can be swallowed smoothly. The mixture of saliva and food in the mouth is called bolus.
- Lubricative function of saliva helps in easy movement through the throat into the food pipe.
- The enzyme amylase (also called ptyalin) helps in breaking down starch into simple sugars to be absorbed in the small intestine. About 30% of the starch digestion takes place in the mouth with the saliva.
- Lipase of the saliva breaks down the fat and helps in its digestion along with the pancreatic lipase.
- Saliva creates a liquid medium for the chemicals to carry the taste sense to the receptors of the tongue. People with reduced secretion of saliva complain of reduced taste too. Excessive amounts of sodium in saliva make everything taste salty.
- Saliva maintains the pH of the mouth between 602 to 704, neither too acidic nor to alkaline. This is important as high acidity can cause minerals of the teeth to dissolve.
- Saliva secretes a chemical called gustin that helps in development of taste buds.
- Saliva also contains a component called EGF (Epidermal Growth Factor) which helps in healing of ulcers of the digestive system, controlling acid secretion in the stomach and mucosal protection from acids that come from stomach, bile, pepsin and trypsin and also chemical and bacterial agents.