saliva
Meaning of saliva: The fluid that keeps the mouth working, protects teeth between meals, and starts breaking down food before it is swallowed.
Definition of saliva
Saliva is the watery fluid produced by glands in and around the mouth, made up mostly of water with dissolved salts, proteins and enzymes. It moistens food so it can be chewed and swallowed, dissolves substances so they can be tasted, neutralizes acid, and holds antibodies and antibacterial proteins. Several liters are produced across a day and most is swallowed.
Where does it come from?
Three pairs of large glands supply most of it. The parotid glands sit in front of the ears and produce a thin watery fluid rich in enzyme. The submandibular glands under the jaw supply the largest share overall. The sublingual glands beneath the tongue produce a thicker, more slippery secretion. Hundreds of tiny glands scattered through the lining of the mouth add a steady trickle that keeps the surface wet between meals. Output rises sharply at the sight, smell or taste of food, driven by nerve signals rather than by hormones.
What is it for?
| Job | How it is done |
|---|---|
| Lubrication | Mucins make the fluid slippery for chewing and speech |
| Starting digestion | Amylase begins breaking starch into sugars |
| Taste | Dissolves food chemicals so taste buds can detect them |
| Protecting teeth | Buffers acid and supplies calcium and phosphate to enamel |
| Defense | Antibodies, lysozyme and other proteins limit bacteria |
What happens when there is too little?
A persistently dry mouth is more than a nuisance. Without the buffering and mineral supply, tooth decay accelerates, often at the gum line and on surfaces normally spared. Fungal infection of the mouth becomes more likely, dentures stop fitting comfortably, and swallowing dry food and speaking at length become difficult. Medicines are the commonest cause, since hundreds reduce output as a side effect. Radiotherapy to the head and neck damages the glands directly, sometimes permanently. Sjogren syndrome, an autoimmune condition, attacks the glands themselves. Dehydration and mouth breathing produce a temporary version.
Can it be used for testing?
Yes, and increasingly so. It is easy to collect without a needle, which suits repeated sampling and children. Hormones such as cortisol, antibodies to certain viruses, genetic material for DNA analysis, and drugs of abuse can all be measured in it. Swelling or persistent lumps in the glands are investigated in their own right, since salivary gland cancer and the far commoner stones and infections all present that way.
Also known as
Used in a sentence
Reduced saliva production following head and neck radiotherapy contributed to rapid dental decay.
Good to know
Reduced saliva accelerates tooth decay because the buffering of acid and the supply of calcium and phosphate to enamel are lost, and medication is the most frequent cause.
Word origin
Where “saliva” comes from
From the Latin saliva, meaning spittle.