Saliva

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

WikiDoc Resources for Saliva
Articles
Most recent articles on Saliva Most cited articles on Saliva Review articles on Saliva Articles on Saliva in N Eng J Med, Lancet, BMJ
Media
Powerpoint slides on Saliva Images of Saliva Photos of Saliva Podcasts & MP3s on Saliva Videos on Saliva
Evidence Based Medicine
Cochrane Collaboration on Saliva Bandolier on Saliva TRIP on Saliva
Clinical Trials
Ongoing Trials on Saliva at Clinical Trials.gov Trial results on Saliva Clinical Trials on Saliva at Google
Guidelines / Policies / Govt
US National Guidelines Clearinghouse on Saliva NICE Guidance on Saliva NHS PRODIGY Guidance FDA on Saliva CDC on Saliva
Books
Books on Saliva
News
Saliva in the news Be alerted to news on Saliva News trends on Saliva
Commentary
Blogs on Saliva
Definitions
Definitions of Saliva
Patient Resources / Community
Patient resources on Saliva Discussion groups on Saliva Patient Handouts on Saliva Directions to Hospitals Treating Saliva Risk calculators and risk factors for Saliva
Healthcare Provider Resources
Symptoms of Saliva Causes & Risk Factors for Saliva Diagnostic studies for Saliva Treatment of Saliva
Continuing Medical Education (CME)
CME Programs on Saliva
International
Saliva en Espanol Saliva en Francais
Business
Saliva in the Marketplace Patents on Saliva
Experimental / Informatics
List of terms related to Saliva

Saliva is the watery and usually frothy substance produced in the mouths of humans and some animals. In animals, saliva is produced in and secreted from the salivary glands.

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 occurs within the mouth, even before food reaches the stomach. Salivary glands also secrete enzyme to start fat digestion. This is useful for infants to digest the fat in milk.

Role in emesis

The importance of the salivary protective function can be demonstrated by considering a scenario where an individual is about to vomit. Vomit contains gastric substances which are extremely acidic and will erode teeth. A protective reflex occurs before the individual prepares to vomit. Signals are sent from the brain to the salivary glands via the involuntary nervous system to cause increased saliva secretion, even before vomiting occurs. Thus, when vomiting does occur, there is already saliva present in the mouth acting to minimize the acidity and thus prevent destruction of tooth structure.

Pellicle deposits

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.

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 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.

Stimulation

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

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 700mL of saliva per day, which is much less than was once thought.

Contents

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

It is a fluid containing:

• Water
• Electrolytes:
  • 2-21 mmol/L sodium (lower than blood plasma)
  • 10-36 mmol/L potassium (higher than plasma)
  • 1.2-2.8 mmol/L calcium
  • 0.08-0.5 mmol/L magnesium
  • 5-40 mmol/L chloride (lower than plasma)
  • 25 mmol/L bicarbonate (higher than plasma)
  • 1.4-39 mmol/L phosphate
• Mucus. Mucus in saliva mainly consists of mucopolysaccharides and glycoproteins;
• Antibacterial compounds (thiocyanate, hydrogen peroxide, and secretory immunoglobulin A)
• Various enzymes. There are three major enzymes found in saliva.
  • α-amylase (EC3.2.1.1). Amylase starts the digestion of starch and lipase fat before the food is even swallowed. It has a pH optima of 7.4.
  • lysozyme (EC3.2.1.17). Lysozyme acts to lyse bacteria.
  • lingual lipase (EC3.1.1.3). Lingual lipase has a pH optimum ~4.0 so it is not activated till entering an acidic environment.
  • Minor enzymes include salivary acid phosphatases A+B (EC3.1.3.2), N-acetylmuramyl-L-alanine amidase (EC3.5.1.28), NAD(P)H dehydrogenase-quinone (EC1.6.99.2), salivary lactoperoxidase (EC1.11.1.7), superoxide dismutase (EC1.15.1.1), glutathione transferase (EC2.5.1.18), class 3 aldehyde dehydrogenase (EC1.2.1.3), glucose-6-phosphate isomerase (EC5.3.1.9), and tissue kallikrein (EC3.4.21.35).
• Cells: Possibly as much as 8 million human and 500 million bacterial cells per mL. The presence of bacterial products (small organic acids, amines, and thiols) causes saliva to sometimes exhibit foul odor.
• Opiorphin, a newly researched pain-killing substance found in human saliva.

External links

• Saliva at the US National Library of Medicine Medical Subject Headings (MeSH)