Spit, Saliva


Saliva is an exocrine secretion that arises in the salivary glands, which are located in the oral cavity.
In humans, there are three large salivary glands and a multitude of small salivary glands. The large salivary glands include the parotid gland (Parotid gland), the submaxillary gland (Submandibular gland) and the sublingual gland (Sublingual gland). Together, these are responsible for about 90% of the saliva formed, the rest is provided by the small salivary glands in the oral mucosa.

On average, a person produces around 500 to 1500 milliliters of saliva per day, depending, among other things, on how much and what type of food they eat. However, even without any food intake, a certain amount of saliva is produced, namely around 500 milliliters, which is known as basal secretion.

Ingredients and texture

Depending on the nature of the saliva, a distinction is made between two different types: There is mucinous (or mucous) Saliva and the serous Saliva. Mucinous saliva is more likely slimy to viscous. This is increasingly produced when the influence of the sympathetic part of the vegetative nervous system predominates.
If, on the other hand, the parasympathetic part is in the foreground, then the saliva is more likely thin to watery and better for that digestion suitable. The type of secretion varies depending on the gland, but since ultimately they all flow into the oral cavity, there is a mixture of the two types of saliva here.

The main component of saliva is waterfrom which he to 99% consists. However, it is the small remaining percentage that, through its composition, ensures that the saliva can fulfill its functions. Most of the ingredients in saliva are Proteins. This is especially important Mucin, a mucous substance that helps keep the mucous membrane from external mechanical, chemical or physical stimuli to protect. In addition, this substance contributes to the fact that the saliva gets its special consistency and the chyme slippery is made. Among the other proteins are, for example, those that take part in the digestive process (Amylases, Ptyalin) and also important parts of the Defense systemnamely mainly antibodies of the class IgA.
In addition, there are many small-molecule components in saliva, namely a large number of them Electrolytes (the most important are the Sodium, potassium, calcium and chloride ions), ammonia, uric acid and urea.

At rest, the pH of saliva is usually around 6.0 to 6.9. With increased secretion, however, this then rises to values ​​up to 7.2, which is due to the fact that with faster saliva flow there is less time to reabsorb sodium ions from the saliva, which means that a larger number of these ions remain in the saliva and there the pH increases.

More precise composition

Saliva is made up of many different components, with the proportions of the respective components differing from unstimulated to stimulated saliva, as well as the place of production, i.e. which salivary gland is responsible for the saliva production, contributes significantly to the composition.

For the most part (95%) saliva consists of water. However, besides water there are also mucilages (Mucin), which for toughness (viscosity) of saliva are responsible. They help to make the saliva smoother and thus facilitate the swallowing process.

There are also many different electrolytes (Sodium, potassium, magnesium, iron, fluoride, copper, phosphate, chloride) in front. Fluoride protects teeth and tooth enamel.

Other small-molecule, solid components found in saliva are Urea, uric acid and ammonia.

There are also enzymes such as the important digestive enzyme Amylase, the Carbonic anhydrase and the Peroxidase. In addition, important antibodies (Immunoglobulin A) as well as blood group components in saliva.

Dead cells of the oral mucosa (epithelial cells) as well as germs (microorganisms) can (physiologically) be found in the saliva of healthy people.

Enzymes in saliva

The pre-digestion of ingested food begins in the mouth. Certain enzymes in saliva are responsible for this.
Alpha-amylase helps us digest starch in the mouth. The amylase works well in the slightly acidic level, for which the HCO3- buffers the saliva to a pH value of 7. The amylase is inactivated by the gastric acid as soon as the saliva has reached the stomach.
Immunoglobulin a and lysozymes are also components of saliva, they serve the immune defense, this is necessary because the ingestion of food represents a potentially dangerous contact with the outside world. Histatin is also present in saliva, which promotes wound healing. Haptocorrin protects vitamin B12 (cobalamin) from acidic stomach acid, so it can be absorbed in the small intestine with the help of the intrinsic factor.

pH of saliva

In its normal state, healthy saliva has (at rest, without eating) a pH value between 6.0 and 6.9. In the case of stimulation, e.g. Through ingestion of food or a smell stimulus, the saliva can rise to pH values ​​of 7.0 to 7.2.
Due to the increased production and thus the faster transport towards the esophagus and stomach, fewer sodium ions can be absorbed from the saliva than is the case in the resting state. The result is a slight shift in the pH value towards the alkaline (basic) pH range.
When eating acidic foods, the secretion increases the most and the pH value therefore shifts most towards a higher value.
The saliva should not be too acidic, otherwise it can attack the teeth.

What is the function of saliva?

The saliva fulfills several important functions in the oral cavity.
On the one hand, it plays an extremely important role in food intake and digestion. First of all, the saliva ensures that the soluble components of the food dissolve, resulting in a thin-flowing chyme that is easier to swallow.
In addition, the saliva starts digesting large carbohydrates in the oral cavity, which are broken down into smaller fragments by the enzyme ptyalin (an amylase). In addition, the saliva fulfills a role in the defense against pathogenic germs such as bacteria, viruses or fungi. It also helps cleanse and disinfect the oral mucosa.
Furthermore, it should be noted that the saliva simply takes over the function of moistening the oral cavity, which may seem unspectacular at first, but what is ultimately the reason why we can speak, taste or even smell properly at all.
Saliva also makes a not insignificant contribution to the health of our teeth: It protects the tooth substance and controls the formation of plaques and at the same time ensures the remineralization of the teeth, as it contains the substances fluoride and rhodanide, which are essential for tooth enamel.

Stimulation of salivation

The messenger substance norepinephrine causes much more viscous, mucous saliva to be produced. Acetylcholine, on the other hand, causes a lot of watery saliva to be squeezed out of the saliva-producing glands. Depending on the stimulation, 0.1 to 4 ml of saliva is secreted per minute. Over the course of the day, this makes 0.5 to 1.5 liters of saliva.
The glandula parotis (parotid gland) makes the serous, i.e. more watery, saliva and the glandula submandibularis (lower jaw salivary gland) makes the more mucinous, i.e. slimy saliva.
In addition to the vegetative nervous system, other stimuli also have an influence on saliva production. Appealing smells and the taste and food stimulate them ("it makes your mouth water").
Massaging the salivary glands also allows more saliva to escape.
When nausea occurs, the production of saliva increases. If vomiting occurs, the saliva is supposed to protect the teeth from stomach acid.
Furthermore, you can stimulate the flow of saliva solely through conditioning (classic conditioning according to Pavlov). A conditional stimulus (such as the clatter of plates) is sufficient to trigger the conditional response to salivation.

Salivary disorders

The disturbances of the salivary secretion can be divided into two large groups: Either too much (hypersalivation) or too little (hyposalivation) saliva is formed. An increased production of saliva occurs physiologically after the occurrence of reflexes that suggest food intake (smell or taste of food), but sometimes also with great excitement.
Insufficient production of saliva can have various causes: Some diseases are associated with restricted saliva secretion (e.g. Sjogren's syndrome), but some drugs and therapies have the same effect. The resulting dry mouth (XerostomiaIn addition to the direct consequences, it usually also leads to a deterioration in the dental status, e.g. tooth decay (see above). If the amount of saliva is normal, but the composition is abnormally changed, it is called dyschyly.

Salivary stones

Salivary stones (sialolithiasis) can be a few millimeters up to centimeters in size. Mostly they are formed in the submandibular gland, less often in the parotid gland and least of all in the sublingual gland.
The stones can be an incidental finding on an X-ray or they can show clinical symptoms.
If the stones are just big enough to fit into the ducts of the glands, they can obstruct the outflow of saliva. This can lead to an inflammation of the salivary gland (sialadenitis). The patient then has a swollen, painful gland.
Salivary stones consist of the same substances that are found in saliva. These include above all calcium carbonate and calcium phosphate.
The cause is often too little drinking. But diseases such as cystic fibrosis (cystic fibrosis) or mumps can also be responsible. The composition of saliva is different and calcium compounds can fail. Therefore, a calcium level that is too high (hypercalcemia) is also a risk for salivary stones.
The first step in the treatment is to stimulate the flow of saliva in order to flush out the stones that are the right size for it (by increasing saliva production). Drinking a lot helps, of course, but also sucking candy and chewing gum.
The ENT doctor can try to remove stones from the corridors by massage. Sometimes extracorporeal shock wave therapy (ESWL) is used, such as with kidney stones.
Stones of a certain size can sometimes only be recovered surgically.
An antibiotic should be prescribed if bacterial inflammation is suspected. Such an inflammation can turn into an abscess or blood poisoning if left untreated.

Read more about this under: Salivary stones

Sour saliva

Normal saliva has a pH value of around 7.0 to 7.2. If the current value is below this, the saliva is too acidic. Common causes are poor diet and heartburn (reflux). The stomach acid rises up the esophagus and leads to over-acidification of the saliva.
There are various reasons for this, for example the changed anatomical nature of the transition from the esophagus to the stomach or obesity. Often this happens at night because the affected person then lies horizontally. Acid saliva also attacks the gums and inflammation occurs more frequently.

Foamy saliva

Foamy saliva has too many mucins (phlegm) and too little fluid.
This happens when the mouth is dry (xerostomia). Often these are older patients who drink too little and take medication that increases the dry mouth. This can impair the sense of taste and make speaking difficult. In addition, it can lead to tartar in those affected.

Sticky saliva

Sticky saliva can occur when suffering from dry mouth. The saliva is too thick and can develop stringy properties.
In the morning, saliva can also have this type of texture, since humans generally produce less saliva at night. Sleeping with your mouth open and snoring encourage this.

HIV transmission through saliva?

Since the infection with HIV is transmitted through body fluids, the question naturally arises as to whether an infection through the saliva (e.g. while kissing) is possible. The answer to this question is: "As a rule: No!"

This is because the amount of virus (concentration) in the saliva is extremely small, and so a huge amount of saliva would have to be absorbed, which is not possible on this scale.

But if one kisser, or even both, have a bleeding wound in their mouth, the likelihood of transmission is increased. Depending on the amount of blood in the saliva (there must be a relatively large amount of blood mixed in) now quite possible.