Saliva

Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be extracted), enzymes (such as lipase and amylase), and antimicrobial agents (such as secretory IgA, and lysozymes).^[1]

The enzymes found in saliva are essential in beginning the process of digestion of dietary starches and fats. These enzymes also play a role in breaking down food particles entrapped within dental crevices, thus protecting teeth from bacterial decay.^[2] Saliva also performs a lubricating function, wetting food and permitting the initiation of swallowing, and protecting the oral mucosa from drying out.^[3]

The process of breaking down dietary carbohydrates and lipids starts with the enzymes present in saliva. In addition to keeping teeth free from bacterial decay, these enzymes aid in the breakdown of food particles stuck in dental fissures. In addition to lubricating food and enabling the start of swallowing, saliva also serves to prevent the mouth mucosa from drying up.Saliva has specialized purposes for a variety of animal species beyond predigestion [3]. Certain swifts construct nests with their sticky saliva. The foundation of bird's nest soup is an aerodramus nest.[4] Venomous saliva injected by fangs is used by cobras, vipers, and certain other members of the venom clade to hunt. Some caterpillars use modified salivary glands to store silk proteins, which they then use to make silk fiber.^[4]

^ Nosek, Thomas M. Essentials of Human Physiology, Section 6, Chapter 4. Archived from the original on 2016-01-17.
^ Fejerskov, O.; Kidd, E. (2007). Dental Caries: The Disease and Its Clinical Management (2nd ed.). Wiley-Blackwell. ISBN 978-1-4051-3889-5.
^ Edgar, M.; Dawes, C.; O'Mullane, D. (2004). Saliva and Oral Health (3 ed.). British Dental Association. ISBN 978-0-904588-87-3.
^ "Insect-produced silk" (PDF). Archived from the original (PDF) on 2017-01-31. Retrieved 2019-04-13.

[ReferenceA-1] Nosek, Thomas M. Essentials of Human Physiology, Section 6, Chapter 4. Archived from the original on 2016-01-17.

[DCDCM-2] Fejerskov, O.; Kidd, E. (2007). Dental Caries: The Disease and Its Clinical Management (2nd ed.). Wiley-Blackwell. ISBN 978-1-4051-3889-5.

[SOH-3] Edgar, M.; Dawes, C.; O'Mullane, D. (2004). Saliva and Oral Health (3 ed.). British Dental Association. ISBN 978-0-904588-87-3.

[4] "Insect-produced silk" (PDF). Archived from the original (PDF) on 2017-01-31. Retrieved 2019-04-13.

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