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Saliva is inhabited by bacteria. Human bite wounds have a high risk of infection unless treated with antibiotics.
Various species have evolved special uses for saliva that go beyond predigestion. Some swifts use their gummy saliva to build their nests. Some Aerodramus swiftlet nests are made only from saliva and used to make bird's nest soup. Cobras, vipers, and certain other members of the venom clade hunt with venomous saliva injected by fangs. Some arthropods, such as spiders and caterpillars, create thread from salivary glands.
Additional recommended knowledge
The digestive functions of saliva include moistening food, and helping to create a food bolus, so it can be swallowed easily. Saliva contains the enzyme amylase that breaks some starches down into maltose and dextrin. Thus, digestion of food occurs within the mouth, even before food reaches the stomach. Salivary glands also secrete enzyme to start fat digestion.
In addition to this, saliva is responsible for depositing salivary pellicle that covers the entirety of the tooth surfaces. This pellicle is believed to play a role in plaque formation, though there is evidence that it may also act as a protective barrier between acids and the tooth surface.
A common belief is that saliva contained in the mouth has natural disinfectants, which leads people to believe it is beneficial to "lick their wounds". Researchers at the University of Florida at Gainesville have discovered a protein called nerve growth factor (NGF) in the saliva of mice. Wounds doused with NGF healed twice as fast as untreated and unlicked wounds; therefore, saliva does have some curative powers in some species. NGF has not been found in human saliva; however, researchers find human saliva contains such antibacterial agents as secretory IgA, lactoferrin, and lactoperoxidase. It has not been shown that human licking of wounds disinfects them, but licking is likely to help clean the wound by removing larger contaminants such as dirt and may help to directly remove infective bodies by brushing them away. Therefore, licking would be a way of washing, useful if purer water isn't available to the animal or person.
The mouth of animals is the habitat of many bacteria, some of which may be pathogenic. Animal (including human) bites are routinely treated with systemic antibiotics because of the risk of septicemia.
The saliva stimulated by sympathetic innervation is thicker, and saliva stimulated parasympathetically is more watery.
Daily salivary output
There has been some disagreement regarding the daily salivary output in a healthy individual. Today, it is believed that the average person produces approximately 0.75 l of saliva per day, less than half of the output originally thought produced.
It is produced at a rate of 1-1.5 l/day. 20ml/hr at rest, 250 ml/hr under stimulated conditions. While sleeping, salivary flow drops to almost zero.
It is a fluid containing:
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Saliva". A list of authors is available in Wikipedia.|