Why do we produce saliva

saliva

What is saliva?

Saliva is the odorless and tasteless secretion of the salivary glands in the oral cavity. It is mainly formed by three large glands: the parotid gland (glandula parotis), which is also placed on both sides (sub-mandibular gland) and the sublingual gland (sublingual gland).

There are also numerous small salivary glands in the cheek, palate and throat mucosa as well as in the base of the tongue.

Saliva Composition

The body produces around 0.5 to 1.5 liters of saliva per day. Composition of the secretion depends on the producing gland:

  • The parotid gland produces “dilution saliva”, a thin, low-protein secretion that makes up about a quarter of the total amount of saliva.
  • The mandibular salivary gland forms a clear, protein-containing and weakly stringy "gliding saliva" that makes up around two thirds of the amount of saliva produced daily.
  • The sublingual salivary gland supplies a protein-rich, stringy "gliding saliva".

One liter of saliva contains a total of 1.4 to 1.6 grams of protein in the form of mucin in the form of mucoproteins (proteins with a carbohydrate content). Mucins form the mucous film on the wall of the oral cavity (as well as the esophagus, stomach and intestines).

The saliva also contains ammonia, uric acid and urea, some folic acid and vitamin C. It also contains electrolytes such as sodium and potassium.

Digestive enzymes are also found in saliva. The most important representative is alpha-amylase (ptyalin), which can break down carbohydrates (starch). It is produced and secreted almost exclusively by the parotid gland - in an amount sufficient to digest all of the starch ingested with food. There is not enough time for this because the food is swallowed relatively quickly (together with the enzyme). In the stomach, the salivary amylase is inactivated by the acidic gastric juice. The amylase from the pancreas then has to take care of the further breakdown of carbohydrates in the small intestine.

Another enzyme in saliva is fat-splitting lipase, which is secreted by the base of the tongue. This enzyme is of particular importance for infants, namely for the digestion of the fat contained in breast milk. This milk fat covers a large part of the energy needs of babies.

Secretion of saliva

The secretion of saliva is triggered reflexively by chemical irritation of the oral mucosa (contact with food) and by mechanical stimuli (chewing). Smell and taste stimuli (such as a good scent of roast meat or lemon), a feeling of hunger and psychogenic factors also trigger salivation.

When we sleep or are dehydrated, very little saliva is released.