Saliva performs various functions: digestive, protective, bactericidal, trophic, mineralizing, immune, hormonal, etc.
Saliva is involved in the early stages of digestion by wetting and softening food. In the oral cavity, under the action of the enzyme α-amylase, the breakdown of carbohydrates occurs.
The protective function of saliva is that, washing the surface of the tooth, the oral fluid constantly changes its structure and composition. At the same time, glycoproteins, calcium, proteins, peptides and other substances are deposited from saliva on the surface of the tooth enamel, which form a protective film - "pellicle", which prevents organic acids from acting on the enamel. In addition, saliva protects the tissues and organs of the oral cavity from mechanical and chemical influences (mucins).
Saliva also performs an immune function due to the secretory immunoglobulin A synthesized by the salivary glands of the oral cavity, as well as immunoglobulins C, D and E of serum origin.
Salivary proteins have nonspecific protective properties: lysozyme (hydrolyzes the β-1,4-glycosidic bond of polysaccharides and mucopolysaccharides containing muramic acid in the cell walls of microorganisms), lactoferin (participates in various body defense reactions and immunity regulation).
Small phosphoproteins, histatins and staterins play an important role in antimicrobial action. Cystatines are inhibitors of cysteine proteinases and may play a protective role in inflammatory processes in the oral cavity.
Mucins trigger a specific interaction between the bacterial cell wall and complementary galactoside receptors on the epithelial cell membrane.
The hormonal function of saliva is that the salivary glands produce the hormone parotin (salivaparotin), which contributes to the mineralization of the hard tissues of the tooth.
The mineralizing function of saliva is essential in maintaining oral homeostasis. Oral fluid is a solution oversaturated with calcium and phosphorus compounds, which underlies its mineralizing function. When saliva is saturated with calcium and phosphorus ions, their diffusion from the oral cavity into the enamel of the tooth occurs, which ensures its "maturation" (compaction of the structure) and growth. The same mechanisms prevent the release of minerals from the tooth enamel, i.e. its demineralization. Due to the constant saturation of the enamel with substances from saliva, the density of the tooth enamel increases with age, and its solubility decreases, which ensures a higher caries resistance of the permanent teeth of the elderly compared to young people.
3. The composition of the secretion of the salivary glands.
About 98% of the total mass of salivary secretion is water; 2% falls on dry residue, about 2/3 of which is organic matter, 1/3 is mineral.
To the mineral components of saliva include cations: calcium, potassium, sodium, magnesium, silicon, aluminum, zinc, iron, copper, etc., as well as anions: chlorides, fluorides, iodides, bromides, thiocyanates, bicarbonates, etc.
The calcium content in saliva is 1.2 mmol / l. At the same time, most (55-60%) of the total calcium in saliva is in an ionized state, the remaining 40-45% of all calcium binds to saliva proteins. In combination with some organic components of saliva, excess calcium salts can be deposited on the teeth, forming tartar, which plays a special role in the development of periodontal disease.
In saliva, the state of supersaturation with hydroxyapatites is constantly maintained, the hydrolysis of which leads to the formation of Ca 2+ and HPO 4 2- ions. Supersaturation with hydroxyapatites is also characteristic of the blood and the whole organism, which allows it to regulate the composition of mineralized tissues.
Saliva has a higher mineralizing ability than blood, since it is oversaturated with hydroxyapatites by 4.5 times, and blood - by 2-3.5 times. It was found that in persons with multiple caries, the degree of saliva oversaturation with hydroxyapatites is 24% lower than in caries-resistant persons. With caries, the sodium content in saliva decreases, and chlorine increases. The content of potassium and sodium in saliva changes significantly during the day.
Mixed saliva contains 0.4-0.9 mmol / L of magnesium. With age, the magnesium content in saliva increases.
Fluoride compounds, which are part of saliva, have the ability to suppress the bacterial flora, and also be included in the composition of dental plaque and fluorapatites of the tooth enamel.
The concentration of inorganic iodine in saliva is about 10 times higher than in blood serum, since the salivary glands concentrate iodine, which is necessary for the synthesis of thyroid hormones.
Thiocyanates are found in saliva. Their content in saliva varies considerably, but they are found even in the saliva of infants. It is believed that thiocyanates perform a protective function, since, along with halogens, they activate peroxidases involved in the metabolism of peroxide compounds. Since the content of thiocyanates in saliva exceeds their content in other biological fluids, it is generally accepted that saliva concentrates thiocyanates. This fact is used in forensic medicine.
Human saliva is a colorless and transparent biological fluid of an alkaline reaction, which is secreted by three large salivary glands: the submandibular, sublingual and parotid, and many small glands located in the oral cavity. Its main components are water (98.5%), trace elements and alkali metal cations, as well as acid salts. By wetting the oral cavity, it helps free articulation, protects the enamel of the teeth from mechanical, heat and cold effects. Under the influence of salivary enzymes, it starts the process of digestion of carbohydrates.
The protective function of saliva is manifested in the following:
- Protection of the oral mucosa from drying out.
- Neutralization of alkalis and acids.
- Due to the content of the protein substance lysozyme in saliva, which has a bacteriostatic effect, the epithelium of the oral mucosa is regenerated.
- Nuclease enzymes, also found in saliva, help protect the body from viral infections.
- Saliva contains enzymes (antithrombin and antithrombinoplastins) that prevent blood from clotting.
- Many immunoglobulins contained in saliva protect the body from the possibility of penetration of pathogens.
The digestive function of saliva is to wet the food bolus and prepare it for swallowing and digestion. All this is facilitated by mucin, which is part of saliva, which glues food into a lump.
Food is present in the oral cavity for an average of about 20 seconds, but despite this, digestion, which begins in the oral cavity, significantly affects the further breakdown of food. After all, when saliva dissolves food substances, it forms taste sensations and significantly affects the awakening of appetite.
Chemical processing of food also takes place in the oral cavity. Under the influence of amylase (an enzyme of saliva), polysaccharides (glycogen, starch) are broken down to maltose, and the next enzyme in saliva, maltase, splits maltose into glucose.
Excretory function. Saliva has the ability to excrete metabolic products of the body. For example, some drugs, uric acid, urea, or mercury and lead salts can be excreted in saliva. All of them leave the human body at the time of spitting out saliva.
Trophic function. Saliva is a biological medium in direct contact with the tooth enamel. It is she who is the main source of zinc, phosphorus, calcium and other trace elements necessary for the preservation and development of teeth.
Recently, the significance of saliva has become even greater - now it is used to diagnose various diseases not only of the oral cavity, but also of the whole organism. All that is needed for this is to collect a few drops of saliva on a cotton swab. Next, a test is carried out, which can reveal the presence of diseases of the oral cavity, the level of alcohol, the hormonal state of the body, the presence or absence of HIV and many other indicators of human health.
This test brings absolutely no discomfort to the patient. Moreover, you can do the research at home by purchasing special kits at the pharmacy, which are designed for self-sampling of saliva analysis. After that, it remains only to send them to the laboratory and wait for the results.
- The process of salivation is subdivided into conditioned reflex and unconditioned reflex mechanisms. The conditioned reflex process can be caused by any kind, smell of food, sounds associated with its preparation, or talking and remembering food. The undoubtedly reflex process of salivation occurs already in the process of food intake into the oral cavity.
- With an insufficient amount of saliva, food debris is not completely washed out of the oral cavity, which leads to yellow staining of the teeth.
- The process of salivation decreases when fright or stress occurs, and stops altogether during sleep or during anesthesia.
- 0.5 - 2.5 liters is the amount of saliva secreted per day, which is necessary for the normal functioning of the human body.
- If a person is in a calm state, then the rate of saliva secretion does not exceed 0.24 ml / min, and in the process of chewing food, it increases to 200 ml / min.
- In people over 55, the salivation process slows down.
- Insect bites are less painful and go away faster if moistened with saliva from time to time.
- To get rid of warts, abscesses and various types of inflammation on the skin, up to ringworm, saliva lotions are used.
- An increased dose of blood sugar negatively affects salivation.
The quality of saliva and the presence of beneficial properties in it directly depends on the general condition of the oral cavity, as well as on the health of teeth and gums in particular. That's why
The leading role among the protective factors of saliva is played by enzymes of various origins - α-amylase, lysozyme, nucleases, peroxidase, carbonic anhydrase, etc. This applies to a lesser extent to amylase, the main enzyme of mixed saliva involved in the initial stages of digestion.
α-Amylase. Salivary amylase cleaves α (1,4) -glycosidic bonds in starch and glycogen. In terms of its immunochemical properties and amino acid composition, salivary α-amylase is identical to pancreatic amylase. Certain differences between these smylases are due to the fact that salivary and pancreatic amylases are encoded by different genes.
α-Amylase is secreted by the secretion of the parotid gland and small labial glands, where its concentration is 648-803 μg / ml and is not associated with age, but changes during the day depending on brushing the teeth and eating.
In addition to α-amylase, the activity of several more glycosidases is determined in mixed saliva - α-L-frucosidase, α- and β-glucosidase, α- and β-galactosidase, neuraminidase, etc.
Lysozyme- a protein, the polypeptide chain of which consists of 129 amino acid residues and is folded into a compact globule. The three-dimensional conformation of the polypeptide chain is supported by 4 disulfide bonds. The lysozyme globule consists of two parts: one contains amino acids with hydrophobic groups (leucine, isoleucine, tryptophan), the other part is dominated by amino acids with polar groups (lysine, arginine, aspartic acid).
Lysozyme is synthesized by epithelial cells of the ducts of the salivary glands. Another source of lysozyme is neutrophils.
Through hydrolytic cleavage of the glycosidic bond in the polysaccharide chain of murein, the bacterial cell wall is destroyed, which forms the chemical basis of the antibacterial action of lysozyme.
The most sensitive to lysozyme are gram-positive microorganisms and some viruses. The formation of lysozyme is reduced in some types of oral diseases (stomatitis, gingivitis, periodontitis).
Carbonic anhydrase- an enzyme of the lyase class. Catalyzes the cleavage of the C-O bond in carbonic acid, which leads to the formation of carbon dioxide and water molecules.
In the acinar cells of the parotid and submandibular salivary glands, type VI carbonic anhydrase is synthesized and secreted into saliva as part of secretory granules.
The secretion of this type of carbonic anhydrase in saliva follows circadian rhythms: its concentration is very low during sleep and increases in the daytime after waking up and having breakfast. Carbonic anhydrase regulates the buffering capacity of saliva.
Peroxidase belong to the class of oxidoreductases and catalyze the oxidation of hydrogen peroxide.
Salivary peroxidase belongs to hemoproteins and is formed in the acinar cells of the parotid and submandibular salivary glands. In the secretion of the parotid gland, the activity of enzymes is 3 aza higher than in the submandibular gland.
The biological role of peroxidases present in saliva is that, on the one hand, the oxidation products of thiocyanates, halogens inhibit the growth and metabolism of lactobacilli and some other microorganisms, and on the other hand, the accumulation of hydrogen peroxide molecules is prevented by many types of streptococci and cells of the oral mucosa ...
Proteinases (salivary proteolytic enzymes). In saliva, there are no conditions for active breakdown of proteins. This is due to the fact that there are no denaturing factors in the oral cavity, and there are also a large number of proteinase inhibitors of a protein nature. The low activity of proteinases allows saliva proteins to be preserved in their native state and to fully perform their functions.
In the saliva of a healthy person, a low activity of acidic and sub-alkaline proteinases is determined. The source of proteolytic enzymes in saliva is mainly microorganisms and leukocytes. Saliva contains trypsin-like, aspartyl, serine and matrix metalloproteinases.
Trypsin-like proteinases cleave peptide bonds, in the formation of which the carboxyl groups of lysine and arginine take part. Of the weakly alkaline proteinases in mixed saliva, kallikrein is the most active.
Protein inhibitors of proteinases... The salivary glands are the source of a large number of secretory proteinase inhibitors. They are represented by cystatines and low molecular weight acid-stable proteins.
Acid-stable protein inhibitors can withstand heating to 90 ° C at acidic pH values without losing their activity. These proteins are able to suppress the activity of kallikrein, trypsin, elastase.
Nucleases play an important role in the protective function of mixed saliva. The main source of them in saliva are leukocytes. In mixed saliva, acidic and alkaline RNAases and DNases, differing in different properties, were found. These enzymes dramatically slow down the growth and reproduction of microorganisms in the oral cavity. In some inflammatory diseases of the soft tissues of the oral cavity, their number increases.
Phosphatase - enzymes of the hydrolase class, which cleave inorganic phosphate from organic compounds. In saliva, they are represented by acidic and alkaline phosphatases.
· Acid phosphatase (pH 4.8) is contained in lysosomes and enters the mixed saliva with the secretions of the large salivary glands, as well as bacteria, leukocytes and epithelial cells. The enzyme activity in saliva, as a rule, increases with periodontitis and gingivitis.
Alkaline phosphatase (pH 9.1 - 10.5). In the secretions of the salivary glands of a healthy person, activity is low. The activity also increases with inflammation of the soft tissues of the oral cavity and caries.
Every day, the human salivary glands produce about one and a half liters of saliva. A person rarely pays attention to this process, it is natural, like breathing or blinking. But when saliva is not produced enough, its deficiency greatly reduces the quality of life and leads to a deterioration in well-being. What is the significance of human saliva for the normal functioning of the body, what are its functions and what it consists of, the article will tell.
General information
Saliva is a clear liquid secreted by the salivary glands and entering the oral cavity through their ducts. There are large salivary glands in the mouth, their names indicate their localization: parotid, sublingual, submandibular glands. In addition to them, there are many small glands located under the tongue, on the lips, cheeks, palate, etc.
From small glands, the secret is released continuously, moisturizing the surface of the mucous membrane. Thanks to this, a person can speak articulately, since the tongue easily slides over the wet shell. The secretion of secretion by large glands occurs at the conditioned reflex level when a person hears the smell of food, thinks about it or sees it.
Interestingly, the thought of lemon increases the production of saliva.
How much saliva a person produces per day is not constant. The volume of secreted secretion can vary from 1.5 to 2 liters. The rate of its production is also not the same.
Interesting: when eating dry food, salivation will be more intense than when absorbing liquid food.
At night, the rate of salivation decreases. The parotid glands almost completely stop working when a person is asleep. About 80% of the secretion produced during sleep falls on the submandibular gland, the remaining 20% is produced by the sublingual glands.
Excreted from the salivary ducts, saliva mixes with the bacteria and products of their vital activity present in the oral cavity. Food particles in the mouth, elements of soft dental plaque are added to it. This mixture is called oral fluid.
Features of the composition
In terms of chemical composition, 99.5% saliva is water. The remaining half a percent is organics and minerals dissolved in it. Among the organic components, it contains the most proteins. Human saliva contains a specific protein, salivoprotein, which contributes to the deposition of calcium and phosphorus ions in the enamel, as well as phosphoprotein, under the influence of which the formation of soft microbial plaque and hard stone occurs.
Human saliva contains an enzyme that breaks down the starch contained in foods - amylase. Another enzyme, lysozyme, protects the body from the harmful effects of various pathogens trying to penetrate it through the oral cavity. Lysozyme has the ability to destroy the membranes of bacterial cells, which explains the antibacterial properties of the enzyme. Other enzymes are also present in the secret: proteinase, phosphatase, lipase.
The following minerals are found in saliva: sodium, calcium, potassium, magnesium, phosphorus, iodine. It contains actoferrin, immunoglobulins, mucin, cystatin, cholesterol. It contains the hormones cortisol, progesterone, estrogen and testosterone.
Scientists have found that the secretion of the salivary glands has a variable composition. What a person's saliva consists of depends on factors such as age, general health, food eaten, and ecology. The composition can be influenced by diseases such as diabetes mellitus, pancreatitis, hepatitis, periodontitis. In older people, the parotid salivary glands produce secretions with an increased calcium content, which explains the accelerated formation of stones in them.
What is pH?
The ratio of acids and alkalis in a liquid is called acid-base equilibrium, for the determination of which there is a special indicator - pH. The abbreviation stands for "power Hydrogen" - "the power of hydrogen." The pH value indicates the number of hydrogen atoms in the solution under study. PH 7 is considered neutral. If the resulting number is less than 7, we speak of an acidic environment. These are all indicators from 0 to 6.9. If the pH value is higher than 7, this indicates an alkaline environment. This includes pH values from 7.1 to 14.
The acidity of saliva is influenced by the rate of its production. So, the pH norm of human saliva can be in the range of 6.8 - 7.4. With intensive salivation, this figure can increase to 7.8. During sleep, during a long conversation, hunger, and anxiety, the secretion of the salivary glands slows down. Because of this, its pH also decreases.
In addition, the acidity of the secretion secreted by different glands is not the same. For example, the parotid glands produce a secretion with a pH of 5.8, and the submandibular glands - 6.4.
Note: When the pH of saliva is low, a person is more likely to develop caries. When the pH changes to the alkaline side (pH 6-6.2), foci of demineralization appear on the teeth with the further formation of carious cavities.
Litmus paper can be used to determine the pH of a healthy person's saliva. A strip of paper is dipped for a few seconds in a container with collected oral fluid, and then the result is evaluated in accordance with the color scale. With litmus papers on hand, you can also carry out the test at home.
Meaning and functions
The functions of saliva are varied. Wetting the mucous membrane is not the only thing a person needs saliva for. The secretion of the salivary glands ensures the health of all anatomical structures and organs located in the oral cavity.
In babies, saliva also performs a protective function, washing out bacteria that have got into it from the oral cavity.
In people suffering from xerostomia or (with these diseases, salivation is impaired), inflammation of the oral mucosa develops, teeth are destroyed by caries. The first condition is due to the fact that, without moisturizing, the oral mucosa becomes susceptible to various kinds of stimuli, its sensitivity increases.
Multiple caries on the teeth develops as a result of the fact that saliva, with violations of its production, is not able to mineralize enamel and natural cleansing of the oral cavity from food debris does not occur. As a rule, within 3-5 months, people with salivary disorders develop numerous dental lesions.
Note: the oral fluid contains calcium and phosphorus ions, they penetrate into the enamel crystal lattice, filling the voids in it.
Excreted when food enters the mouth, saliva moistens it and facilitates the passage of the food lump from the oral cavity into the esophagus. But the digestive function of the secret does not end there. The enzymes contained in its composition provide the primary breakdown of carbohydrates.
An interesting fact: studies of the secretion of the salivary glands make it possible to determine the presence of systemic diseases in a person. In a healthy person, saliva crystals are arranged in a chaotic manner, while in a patient they are lined up in bizarre patterns. For example, with allergies, the crystals form a fern-leaf-like shape. This property could be used for early diagnosis of many diseases.
Another function of saliva is healing. It has been proven that it contains antibacterial substances that promote the healing of various mucosal injuries. Many have noticed that mouth wounds disappear quickly.
Oral fluid also plays an important role in articulation. If the mucous membrane was not moistened, the person would not be able to articulate, intelligibly speak.
Without the secretion of the salivary glands, the course of many vital processes becomes impossible, which means that the general state of human health worsens.
Saliva(lat. saliva) is a colorless liquid secreted into the oral cavity by the salivary glands.
The characteristics of saliva secreted by different salivary glands are somewhat different. An integral characteristic is important for physiology, therefore, the so-called mixed saliva.
Characteristics of human saliva
The mixed saliva of a healthy person under normal conditions is a viscous, slightly opalescent liquid. 99.4–99.5% of human saliva is water. The remaining 0.5–0.6% are organic and inorganic components. Among organic substances: proteins (1.4-6.4 g / l), mucin (mucus) (0.8-6.0 g / l), cholesterol (0.02-0.5 g / l), glucose (0.1-0.3 g / l), ammonium (0.01-0.12 g / l), uric acid (0.005-0.03 g / l). From inorganic substances in saliva are presented anions of chlorides, bicarbonates, sulfates, phosphates; cations of sodium, potassium, calcium, magnesium, as well as trace elements: iron, copper, nickel, etc.The most important enzymes of saliva are amylase and maltase, which act only in a weakly alkaline environment. Amylase breaks down starch and glycogen to maltose. Maltase breaks down maltose to glucose. Saliva also contains proteinases, lipases, phosphatases, lysozyme, etc.
The acidity of saliva depends on the rate of salivation. Typically, the acidity of mixed human saliva is 6.8–7.4 pH, but at high salivation rates it reaches 7.8 pH. The acidity of the saliva of the parotid glands is 5.81 pH, submandibular - 6.39 pH. The density of saliva is 1.001–1.017.
Salivation
Salivation or salivation (lat. salivatio) is carried out by a variety of salivary glands, among which there are three pairs of so-called large salivary glands ... The largest of these are the parotid salivary glands. They are located below and in front of the auricle directly under the skin. Their mass is 20–30 g. Medium-sized - submandibular salivary glands with a mass of about 15 g. The smallest of the large salivary glands are the sublingual glands. Their weight is about 5 g and they are located under the mucous membrane of the floor of the mouth. The rest of the glands are small.Outside of food intake, the salivary glands secrete a total of saliva at a rate of 0.3–0.4 ml / min. The rate of basal salivation is from 0.08 to 1.83 ml / min, stimulated by food - from 0.2 to 5.7 ml / min. The total amount of saliva secreted per day in a healthy person is 2–2.5 liters. Parotid glands secrete 25–35% of the total volume, submandibular glands - 60–70%, sublingual glands - 4–5%, small 8–10%. The saliva of the small glands is characterized by an increased content of mucus. Secreting no more than 10% of the total volume of saliva, they secrete 70% of all mucus.
The amount, chemical composition and characteristics of saliva vary depending on the type of food taken and other factors (smoking, taking medications), as well as with various diseases.
Salivation in children
Salivation in children under three months is insignificant and amounts to 0.6–6 ml of saliva per hour (with active sucking - up to 24 ml per hour). Starting from the age of 3 - 6 months, salivation in a child increases significantly, reaching a volume close to that of adults by the age of 7. In school-age children, the volume of unstimulated saliva secretion ranges from 12 to 18 ml per hour. In children, the acidity of mixed saliva is on average 7.32 pH (in adults - 6.40 pH).Saliva functions
Saliva performs a number of important functions for the body: digestive, protective, remineralizing, trophic, buffering and others.Saliva moistens, liquefies, dissolves food. With the participation of saliva, a food lump is formed. Saliva dissolves substrates for their further hydrolysis. The most active enzymes of saliva are amylase, which breaks down polysaccharides and maltase, which breaks down maltose and sucrose to monosaccharides.
Moisturizing and covering the mucous membrane of the oral cavity with the mucus contained in saliva protects the mucous membrane from drying out, cracking and exposure to mechanical irritants. Washing teeth and oral mucosa, saliva removes microorganisms and products of their metabolism, food debris. The bactericidal properties of saliva are manifested due to the presence of lysozyme, lactoferrin, lactoperoxidase, mucin, cystatins in it.
This process of remineralization of dental tissues is based on mechanisms that prevent the release of its components from the enamel and facilitate their entry from saliva into enamel. Saliva at normal acidity (pH 6.8 to 7.0) is oversaturated with ions, especially Ca 2+ and PO 4 3+ ions, as well as hydroxyapatite (the main component of tooth enamel). With an increase in acidity (decrease in pH), the solubility of enamel hydroxyapatite in the oral fluid increases significantly. Saliva also contains mumps, which increases dental calcification.
Saliva is distinguished by its high buffering properties, allowing it to neutralize acids and alkalis and, thus, to protect tooth enamel from damaging effects.
Scientific research, considering, inter alia, the issues of salivation and characteristics of saliva in diseases of the gastrointestinal tract
- Maev I.V., Barer G.M., Busarova G.A., Pustovoit E.V., Polikanova E.N., Burkov S.G., Yurenev G.L. Dental manifestations of gastroesophageal reflux disease // Clinical Medicine. - 2005. - No. 11. P. 33–38.
- V.P. Novikova, A.M. Shabanov The state of the oral cavity in patients with gastroesophageal reflux disease (GERD) // Gastroenterology of St. Petersburg. - 2009. - No. 1. - with. 25-28.
- E.V. Pustovoit, E.N. Polikanova Changes in indicators of mixed saliva in patients with gastroesophageal reflux disease against the background of antireflux therapy // Russian stamotology. - No. 3. - 2009.
- Egorova E.Yu., Belyakov A.P., Krasnova E.E., Chemodanov V.V. Metabolic profile of blood and saliva in gastroduodenal diseases in children // Bulletin of IvGMA. - Issue. 3. - 2005.S. 13-19.
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