Saliva is a clear, colorless liquid. This is the secret of the salivary glands secreted into the oral cavity. It provides a perception of taste, promotes articulation, lubricates chewed food. In addition, saliva has bactericidal properties, cleanses the oral cavity, protects teeth from damage. Due to the enzymes present in the secretion in the mouth, digestion of carbohydrates begins. The article will discuss the composition and functions of human saliva.
Characterization of the salivary glands
These glands, located in the anterior part of the digestive tract, play a role in ensuring the good condition of the human oral cavity and are directly involved in the digestion process. The salivary glands in medicine are usually divided into small and large. The former include the buccal, molar, labial, lingual, palatine, but we are more interested in the large salivary glands, because salivary secretion mainly occurs in them.
These organs of secretion include sublingual, submandibular, parotid glands. The first, as the name implies, are located in the hyoid fold under the mucous membrane of the oral cavity. Submandibular located in the lower 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 secrete saliva, 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 consists of 98.5 percent of water, and also contains trace elements, salts of various acids, alkali metal cations, some vitamins, lysozyme and other enzymes. The main organic substances in the composition are proteins that are synthesized in the salivary glands. Some proteins are of whey origin.
Enzymes
Of all the substances that make up human saliva, the most interesting are enzymes. These are organic substances that have a protein origin, which are formed in the cells of the body and accelerate the chemical processes that occur in them. It should be noted that no chemical changes occur in the enzymes, they serve as a kind of catalyst, but at the same time they fully retain their composition and structure.
What enzymes are in saliva? The main ones are maltase, amylase, ptyalin, peroxidase, oxidase and other protein substances. They perform important functions: they facilitate the thinning of food, produce its initial chemical treatment, form a food lump, and envelop it with a special mucous substance - mucin. To put it simply, the enzymes that make up saliva make it easier to swallow food and its passage into the stomach through the esophagus. It is necessary to remember one nuance: food with normal chewing is in the mouth for only twenty to thirty seconds, and then enters the stomach, but salivary enzymes even after this continue to exert an effect on the food lump.
According to scientific studies, enzymes in total act on food for about thirty minutes, up to the moment when gastric juice begins to form.
Other substances in the composition
The vast majority of people in saliva have group-specific antigens that correspond to blood antigens. Also, specific proteins were found in it - phosphoprotein, which is involved in the formation of plaque on teeth and tartar, and salivoprotein, which promotes the deposition of phosphorus-calcium compounds on 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, wetting and softening food, provides the formation of a food lump and makes the process of swallowing easier. After being soaked in secretion, food undergoes an initial chemical treatment already in the oral cavity, during which α-amylase carbohydrates partially hydrolyze 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 worked out a secret, it mixed with other substances and formed saliva. What happens next? Saliva begins to prepare food for subsequent digestion in the duodenum and stomach. Moreover, each enzyme that is part of the saliva accelerates this process several times, breaking down into small elements (monosaccharides, maltose) the individual components of the products (polysaccharides, proteins, carbohydrates).
In the process of scientific research, it was revealed that, in addition to thinning food, human saliva has other important functions. So, it cleanses the oral mucosa and teeth from pathogenic microorganisms and their metabolic products. The protective role is also played by immunoglobulins and lysozyme, which are included in the biochemical composition of saliva. As a result of secretory activity, the oral mucosa is moistened, and this is a necessary condition for bilateral transportation of chemicals between the saliva and oral mucosa.
Fluctuations in composition
The properties and chemical composition of saliva vary depending on the speed and nature of the secretion pathogen. For example, when using sweets, cookies, the level of lactate and glucose in mixed saliva temporarily increases. In the process of stimulating salivation in secret, the concentration of sodium, bicarbonates increases significantly, the level of iodine and potassium decreases slightly. The composition of the saliva of a person who smokes includes several times more rhodanides compared to non-smokers.
The content of certain substances varies with certain pathological conditions and diseases. The chemical composition of saliva undergoes daily fluctuations and depends on age, for example, calcium levels increase significantly in older people. Changes may be associated with intoxication and medication. So, a sharp decrease in salivation occurs during dehydration; with diabetes, the amount of glucose increases; in 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
Normally, up to two liters of saliva are released per day in an adult, while the secretion rate is uneven: during sleep, it is minimal (per minute - less than 0.05 milliliters), during wakefulness - per minute about 0.5 milliliters, with stimulation of salivation - per minute up to 2.3 milliliters. The secret secreted by each gland in the oral cavity is mixed into a single substance. The oral fluid (or mixed saliva) is characterized by the presence of constant microflora, consisting of bacteria, spirochetes, fungi, their metabolic products, as well as salivary bodies (leukocytes that migrated into the oral cavity mainly through the gums) and deflated epithelial cells. The composition of saliva, in addition, includes discharge from the nasal cavity, sputum, red blood cells.
Salivation Features
Salivation is controlled by the autonomic nervous system. In the medulla oblongata there are its centers. When stimulating parasympathetic endings, a large amount of saliva is formed, which has a low protein content. Conversely, sympathetic stimulation involves the secretion of a small amount of viscous fluid.
Separation of saliva decreases due to fear, stress, dehydration, it almost stops when a person is sleeping. Enhanced separation occurs under the influence of taste and olfactory stimuli and as a result of mechanical irritation by large particles of food when chewing.