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Saliva (also referred to as spit or spittle) is the watery and usually frothy substance produced in the mouths of humans and most other animals. Saliva is produced in and secreted from the salivary glands. Human saliva is composed mostly of water, but also includes electrolytes, mucus, antibacterial compounds, and various enzymes. [1] As part of the initial process of food digestion, the enzymes in the saliva break down some of the starch and fat in the food at the molecular level. Saliva also breaks down food caught in the teeth, protecting them from bacteria that cause decay. Furthermore, saliva lubricates and protects the teeth, the tongue, and the tender tissues inside the mouth. Saliva also plays an important role in tasting food by trapping thiols produced from odourless food compounds by anaerobic bacteria living in the mouth. [2]

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.[3] 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.

Contents

Functions

Digestion

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 begins in the mouth. Salivary glands also secrete enzymes (salivary lipase) to start fat digestion.[4]

Disinfectants

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 can help to heal wounds 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 peroxidase.[5] 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 wiping off pathogens, useful if clean water is not available to the animal or person.

The mouth of animals is the habitat of many bacteria, some pathogenic. Some diseases, such as herpes, can be transmitted through the mouth. Animal (including human) bites are routinely treated with systemic antibiotics because of the risk of septicemia.

Recent research suggests that the saliva of birds is a better indicator of avian influenza than are faecal samples. [6]

Non-physiological use

Saliva has anti-fog functions. Scuba divers commonly smear a thin layer of saliva on the inside surface of their goggles to prevent fogging.

Saliva is an effective cleaning agent used in art conservation. Cotton swabs coated with saliva are rolled across a painting's surface to delicately remove thin layers of dirt that may accumulate.[7]

Stimulation

The production of saliva is stimulated both by the sympathetic nervous system and the parasympathetic.[8]

The saliva stimulated by sympathetic innervation is thicker, and saliva stimulated parasympathetically is more watery.

Parasympathetic stimulation leads to acetylcholine (ACh) release onto the salivary acinar cells. ACh binds to muscarinic receptors and causes an increased intracellular calcium ion concentration (through the IP3/DAG second messenger system). Increased calcium causes vesicles within the cells to fuse with the apical cell membrane leading to secretion formation. ACh also causes the salivary gland to release kallikrein, an enzyme that converts kininogen to lysyl-bradykinin. Lysyl-bradykinin acts upons blood vessels and capillaries of the salivary gland to generate vasodilation and increased capillary permeability respectively. The resulting increased blood flow to the acinar allows production of more saliva. Lastly, both parasympathetic and sympathetic nervous stimulation can lead to myoepitheilium contraction which causes the expulsion of secretions from the secretory acinus into the ducts and eventually to the oral cavity.

Daily salivary output

There is much debate about the amount of saliva that is produced in a healthy person per day. The estimates range from 0.75 liters per day to 1.5 liters per day. This suggests that the amount produced varies from person to person. However, it is generally accepted that while sleeping the amount usually drops to almost zero.

Contents

Produced in salivary glands, human saliva is 98% water, but it contains many important substances, including electrolytes, mucus, antibacterial compounds and various enzymes. [9]

It is a fluid containing:

Different reagents used to determine the content of saliva \1. Molisch test gives a positive result of purple color that is costituent to the presence of carbohydrates

References

  1. ^ Physiology at MCG 6/6ch4/s6ch4_6
  2. ^ Christian Starkenmann, Benedicte Le Calvé, Yvan Niclass, Isabelle Cayeux, Sabine Beccucci, and Myriam Troccaz. Olfactory Perception of Cysteine−S-Conjugates from Fruits and Vegetables. J. Agric. Food Chem., 2008; 56 (20): 9575-9580 DOI: 10.1021/jf801873h
  3. ^ Marcone, M. F. (2005). "Characterization of the edible bird's nest the Caviar of the East." Food Research International 38:1125–1134. doi:10.1016/j.foodres.2005.02.008 Abstract retrieved 12 Nov 2007
  4. ^ Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1. 
  5. ^ Jorma Tenovuo: Antimicrobial Agents in Saliva—Protection for the Whole Body. Journal of Dental Research 2002, 81(12):807-809
  6. ^ "Saliva swabs for bird flu virus more effective than faecal samples" German Press Agency December 11, 2006 Retrieved 13 November 2007
  7. ^ "Techniques for Cleaning Acrylic". Golden Artist Colors. http://www.goldenpaints.com/justpaint/jp5article2.php. Retrieved on 2008-09-12. 
  8. ^ Physiology at MCG 6/6ch4/s6ch4_7
  9. ^ Physiology at MCG 6/6ch4/s6ch4_6
  10. ^ a b c d Page 928 in: Walter F., PhD. Boron (2003). Medical Physiology: A Cellular And Molecular Approaoch. Elsevier/Saunders. pp. 1300. ISBN 1-4160-2328-3. 

Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

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Wikipedia

See also salivă

Contents

English

Etymology

From Latin salīva.

Pronunciation

  • enPR: sə-līʹ-və IPA: /səˈlaɪvə/, SAMPA: /s@"laIv@/
    Rhymes: -aɪvə

Noun

Singular
saliva

Plural
salivae

saliva (plural salivae)

  1. (physiology) A clear, slightly alkaline liquid secreted into the mouth by the salivary glands and mucous glands, consisting of water, mucin, protein, and enzymes, It moistens the mouth, lubricates ingested food, and begins the breakdown of starches.

Synonyms

Derived terms

Related terms

Translations

See also

Anagrams


Italian

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Italian Wikipedia has an article on:
Saliva

Wikipedia it

Pronunciation

  • IPA: [saˈliː.va], /saˈliva/, SAMPA: /sa"liva/
  • Hyphenation: sa‧lì‧va

Noun

saliva f. (plural salive)

  1. (physiology) saliva, spittle, spit

Related terms

Verb

saliva

  1. third person singular imperfect tense of salire
  2. third-person singular present tense of salivare
  3. second-person singular imperative of salivare

Romanian

Noun

saliva f. (singular, nominative/accusative, definite form of salivă)

  1. the saliva

Spanish

Noun

saliva f. (plural salivas)

Singular
saliva f.

Plural
salivas f.

  1. saliva, spittle

Simple English

Saliva is the watery substance made in the mouths of humans and some animals. Saliva begins digesting food in the mouth, and moistens food to make swallowing easier. Saliva is sometimes called "spit."

It can be used as a defense by animals such as Llamas, but "spitting" at a nasty, mean predator.

Spit comes out people's mouths.

Spit is thought to be able to help wounds heal faster.








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