The composition of human saliva

Saliva is a clear liquid that does not have color. This is the secret of the salivary glands, which is separated into the oral cavity. It provides a perception of taste, promotes articulation, lubricates the chewed food. In addition, the saliva has bactericidal properties, cleans the mouth, protects the teeth from damage. Due to the enzymes present in the secretion, digestion of carbohydrates begins in the mouth. The article will deal with the composition and functions of human saliva.

Characteristics of the salivary glands

These glands located in the anterior part of the digestive tract play a role in ensuring a good condition of the human oral cavity and directly participate in the digestive process. Salivary glands in medicine are divided into small and large. The first include buccal, molar, labial, lingual, palatine, but we are more interested in large salivary glands, because salivation mainly occurs in them.

These secretions include sublingual, submaxillary, parotid gland. The first, as follows from the name, are located in the hyoid fold under the oral mucosa. Submandibular ones are in the lower part of the jaw. The largest are the parotid glands, consisting of several lobules.

It should be noted that both small and large salivary glands do not directly salivate, they produce a special secret, and saliva is formed when this secret in the oral cavity is mixed with other elements.

Biochemical composition

Saliva has an acidity level of 5.6 to 7.6 and is 98.5 percent water, and also contains trace elements, salts of various acids, cations of alkaline metals, some vitamins, lysozyme and other enzymes. The basic organic substances in the composition are proteins that are synthesized in the salivary glands. Some proteins are of serum origin.

Enzymes

Of all the substances that make up human saliva, the greatest interest is represented by enzymes. These are organic substances having a protein origin, which are formed in the cells of the body and accelerate the chemical processes taking place in them. It should be noted that in the enzymes there are no chemical changes, they serve as a certain catalyst, but at the same time fully retain their composition and structure.

What enzymes are part of the saliva? The main ones are maltase, amylase, ptyalin, peroxidase, oxidase and other protein substances. They perform important functions: they promote the liquefaction of food, produce its chemical initial processing, form a food lump and a special mucous substance - mucin - envelop it. To put it more simply, the enzymes that make up the saliva facilitate the ingestion of food and its passage into the stomach through the esophagus. It is necessary to remember one nuance: the food with normal chewing is in the mouth only for twenty to thirty seconds, and then gets into the stomach, but the salivary enzymes even after that continue to have an effect on the food lump.

According to scientific research, enzymes in total affect the food for about thirty minutes, until the moment when the gastric juice begins to form.

Other substances in the composition

The vast majority of people in saliva have group-specific antigens, which correspond to blood antigens. It also detected specific proteins - phosphoprotein, involved in the formation of plaque on the teeth and tartar, and salivoprotein, which facilitates the deposition of phosphorocalcium compounds on the teeth.

In small amounts, the composition of saliva includes cholesterol and its esters, glycerophospholipids, free fatty acids, hormones (estrogens, progesterone, cortisol, testosterone), as well as various vitamins and other substances. Minerals are represented by anions of chlorides, bicarbonates, iodides, phosphates, bromides, fluorides, cations of sodium, magnesium, iron, potassium, calcium, strontium, copper, etc. Saliva, moistening and softening food, ensures the formation of a food lump and makes the ingestion easier. Food after being impregnated with a secret is subjected to initial chemical treatment already in the oral cavity, during which α-amylase carbohydrates are partially hydrolyzed to maltose and dextrins.

Functions

We have already touched on the functions of saliva, but now we will talk about them in more detail. So, the glands developed a secret, it mixed with other substances and formed saliva. What happens next? Saliva begins to prepare food for later digestion in the duodenum and stomach. Moreover, each enzyme that is part of the saliva, accelerates this process at times, splitting into small elements (monosaccharides, maltose), individual components of the products (polysaccharides, proteins, carbohydrates).

In the course of scientific research it was revealed that, apart from liquefying food, human saliva has other important functions. So, it clears the oral mucosa and teeth from pathogenic microorganisms and the products of their metabolism. A protective role is played by immunoglobulins and lysozyme, which are part of the biochemical composition of saliva. As a result of secretory activity, the oral mucosa is moistened, and this acts as a necessary condition for bilateral transportation of chemicals between saliva and the oral mucosa.

Fluctuations in composition

Properties and chemical composition of saliva vary depending on the speed and nature of the pathogen. For example, with the use of sweets, cookies, the level of lactate and glucose in the mixed saliva temporarily increases. In the process of stimulation of salivation secretively, the concentration of sodium, bicarbonates significantly decreases, the level of iodine and potassium decreases slightly. The composition of human saliva that smokes includes several times more thiocyanates compared to non-smokers.

The content of certain substances varies with certain pathological conditions and diseases. The chemical composition of saliva is subject to daily fluctuations and depends on age, for example, in the elderly, the level of calcium significantly increases. Changes can be associated with intoxication and taking medications. Thus, a sharp decrease in salivation occurs during dehydration; In diabetes mellitus, the amount of glucose increases; In the case of uremia, the content of residual nitrogen increases . When the composition of saliva changes, the risk of dental diseases and digestive disorders increases.

Secretion

In norm for a day in the adult person it is allocated up to two liters of a saliva, thus the rate of secretion is non-uniform: during a dream it is minimal (in a minute - less than 0,05 milliliters), at wakefulness - in a minute about 0,5 milliliters, at stimulation of salivation - Per minute up to 2.3 milliliters. The secret secreted by each gland in the mouth is mixed into a single substance. Oral fluid (or mixed saliva) is characterized by the presence of a constant microflora consisting of bacteria, spirochaetes, fungi, the products of their metabolism, as well as salivary bodies (leukocytes that migrated into the oral cavity mainly through the gum) and deflated epithelial cells. The composition of saliva, in addition, includes discharge from the nasal cavity, sputum, erythrocytes.

Features of salivation

Salivation is controlled by the autonomic nervous system. In the medulla oblongata are its centers. When stimulating parasympathetic endings, a large amount of saliva, which has a low protein content, is formed. Conversely, sympathetic stimulation results in the secretion of a small amount of viscous fluid.

Separation of saliva decreases due to fright, stress, dehydration, it almost stops when a person sleeps. The enhancement of separation occurs under the influence of taste and olfactory stimuli and as a result of the mechanical stimulation produced by large particles of food during chewing.