Saliva is a clear, colorless liquid. This is the secret of the salivary glands, separated into the oral cavity. It provides the perception of taste, promotes articulation, lubricates chewed food. In addition, saliva has bactericidal properties, cleans the oral cavity, and protects teeth from damage. Due to the enzymes present in the secretion, the digestion of carbohydrates begins in the mouth. The article will discuss the composition and functions of human saliva.
Characteristics of salivary glands
These glands, located in the anterior digestive tract, play a role in maintaining the he alth of the human oral cavity and are directly involved in the process of digestion. Salivary glands in medicine are usually divided into small and large. The former include buccal, molar, labial, lingual, palatal, but we are more interested in the major salivary glands because salivation mainly occurs in them.
These organs of secretion include sublingual, submandibular, parotid glands. The first, as the name implies, are located in the sublingual fold under the oral mucosa. The submandibular are in the lower partjaws. 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 is mixed with other elements in the oral cavity.
Biochemical composition
Saliva has an acidity level of 5.6 to 7.6 and consists of 98.5 percent water, and also contains trace elements, s alts 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 of the proteins are of whey origin.
Enzymes
Of all the substances that make up human saliva, enzymes are of the greatest interest. These are organic substances of protein origin, which are formed in the cells of the body and accelerate the chemical processes occurring in them. It should be noted that no chemical changes occur in 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 m altase, amylase, ptyalin, peroxidase, oxidase and other protein substances. They perform important functions: they contribute to the liquefaction of food, produce its initial chemical processing, form a food lump and envelop it with a special mucous substance - mucin. To put it simply, the enzymes that make up saliva,facilitate swallowing food and its passage into the stomach through the esophagus. One caveat must be remembered: during normal chewing, food is in the mouth for only twenty to thirty seconds, and then enters the stomach, but salivary enzymes continue to have an effect on the food bolus even after that.
According to scientific studies, enzymes act on food for a total of about thirty minutes, up to the point where stomach acid begins to form.
Other ingredients
The vast majority of people have group-specific antigens in saliva that correspond to blood antigens. Also, specific proteins were found in it - a phosphoprotein involved in the formation of plaque on the teeth and tartar, and salivoprotein, which contributes to the deposition of phosphorocalcium compounds on the teeth.
Saliva contains small amounts of cholesterol and its esters, glycerophospholipids, free fatty acids, hormones (estrogen, progesterone, cortisol, testosterone), as well as various vitamins and other substances. Minerals are represented by anions of chlorides, bicarbonates, iodides, phosphates, bromides, fluorides, sodium, magnesium, iron, potassium, calcium, strontium, copper, etc. anions. Saliva, wetting and softening food, ensures the formation of a food lump and makes it easier to swallow. After soaking with a secret, food undergoes initial chemical processing already in the oral cavity, during which carbohydrates are partially hydrolyzed to m altose and dextrins by α-amylase.
Functions
We have already touched on the functions of saliva above, but now let's 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 subsequent digestion in the duodenum and stomach. At the same time, each enzyme that is part of saliva accelerates this process several times, splitting individual components of products (polysaccharides, proteins, carbohydrates) into small elements (monosaccharides, m altose).
In the process of scientific research, it was revealed that, in addition to diluting food, human saliva has other important functions. So, it cleans the oral mucosa and teeth from pathogenic microorganisms and their metabolic products. A protective role is also 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 is a necessary condition for the bilateral transport of chemicals between saliva and the oral mucosa.
Squad fluctuations
The properties and chemical composition of saliva change depending on the speed and nature of the causative agent of secretion. For example, when eating sweets, cookies, the level of lactate and glucose in mixed saliva temporarily increases. In the process of stimulating salivation in the 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 contains several times more thiocyanatecompared to non-smokers.
The content of certain substances changes under 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 increases significantly. Changes may be associated with intoxication and medication. So, a sharp decrease in salivation occurs with dehydration; in diabetes, 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 disease and indigestion increases.
Secretion
Normally, up to two liters of saliva are secreted per day in an adult, while the secretion rate is uneven: during sleep it is minimal (less than 0.05 milliliters per minute), while awake - about 0.5 milliliters per minute, with stimulation of salivation - per minute up to 2, 3 milliliters. The secret secreted by each gland is mixed into a single substance in the oral cavity. The oral fluid (or mixed saliva) is distinguished by the presence of a permanent 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 descended epithelial cells. The composition of saliva, in addition, includes discharge from the nasal cavity, sputum, red blood cells.
Features of salivation
Salivation is controlled by the autonomic nervous system. Its centers are located in the medulla oblongata. Atstimulation of parasympathetic endings, a large amount of saliva is formed, which has a low protein content. Conversely, sympathetic stimulation causes the secretion of a small amount of viscous fluid.
Salivation decreases due to fear, stress, dehydration, it almost stops when a person sleeps. Strengthening of separation occurs under the influence of gustatory and olfactory stimuli and as a result of mechanical irritation produced by large food particles during chewing.
