Human saliva

Human saliva is a secret that is secreted by salivary glands (large and small). The total volume of saliva produced during the day ranges from 1,000 to 1,500 ml (pH 6.2 - 7.6). At rest, saliva usually has an acidic reaction, while functioning - alkaline. The viscosity of saliva depends largely on the type of stimulant and the rate of saliva secretion.

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Composition of saliva

Saliva contains the enzyme alpha-amylase, protein, salts, ptyalin, a variety of inorganic substances; anions of Cl, cations of Ca, Na, and K. The dependence between their content in saliva and blood serum is established. In the secret of SJ, small amounts of thiocyanin are detected, which is an enzyme and activates ptyalin in the absence of NaCl. Saliva has an important ability - to clean the oral cavity and thereby improve its hygiene. However, a more important and significant factor is the ability of saliva to regulate and maintain the water balance. The structure of salivary glands is arranged so that they usually stop salivating as the amount of fluid in the body decreases. In this case, thirst and dryness in the mouth appear.

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Selection of saliva

Parotid salivary gland produces a secret in the form of serous fluid and does not produce mucus. The submaxillary salivary gland and, to a greater extent, the sublingual gland, in addition to the serous fluid, also produce mucus. The osmotic pressure of the secretion is usually low, it rises as the rate of secretion increases. The only ptyalin enzyme, produced in the parotid and submandibular SJ, participates in the cleavage of starch (the optimal condition for its cleavage is pH 6.5). The ptyalin is inactivated at pH less than 4.5, as well as at high temperature.

The secretory activity of the salivary gland depends on many factors and is determined by such concepts as conditioned and unconditioned reflexes, hunger and appetite, the mental state of a person, as well as the mechanisms that arise during meals. All functions in the body are interrelated. The act of food intake is associated with visual, olfactory, taste, emotional and other functions of the body. Food, irritating with its physical and chemical agents nerve endings of the oral mucosa, causes an unconditioned reflex pulse, which is transmitted to the cerebral cortex and the hypothalamic region along the nerve pathways, stimulating the chewing center and salivating. Mucin, zymogen and other enzymes enter the cavity of the alveoli, then into the salivary ducts, which stimulate the nerve pathways. Parasympathetic innervation contributes to the release of mucin and secretory activity of the cells of the channels, sympathetic - controls serous and myoepithelial cells. When eating tasty food, saliva contains a small amount of mucin and enzymes; when receiving acidic products in saliva, a high protein content is determined. Tasteless foods and certain substances, such as sugar, lead to the formation of a watery secret.

The act of chewing is due to the nervous regulation of the brain through the pyramidal tract and its other structures. Coordination of chewing food is carried out by nervous impulses going from the oral cavity to the motor unit. The amount of saliva necessary for chewing food creates a condition for normal digestion. Saliva moistens, envelops and dissolves the forming food lump. Reduction of salivation until the complete absence of saliva develops in certain diseases of the SC, for example, with Mikulich disease. Also, abundant salivation causes local irritation of the mucosa, stomatitis, gum disease and teeth and adversely affects prosthesis and metal structures in the mouth, causes dehydration. Change in secretion of SJ leads to a violation of gastric secretion. Synchronicity in the work of paired SS is not sufficiently studied, although there are indications of its dependence on a number of factors, for example, on the condition of the teeth on different sides of the dentition. At rest, the secret is released slightly, in the period of irritation - intermittently. In the process of digestion, the salivary glands periodically activate their activity, which many researchers associate with the transition of gastric contents into the intestine.

How is saliva secreted?

The mechanism of secretion of the secretion of the salivary gland is not entirely clear. For example, with denervation of parotid SLE after the administration of atropine, an intensive secretory effect develops, however, the quantitative composition of the secret does not change. With age, the chlorine content decreases in the saliva, the amount of calcium increases, the pH of the secretion changes.

Numerous experimental and clinical studies show that there is a connection between the SC and the glands of internal secretion. Experimental studies have shown that parotid SLE earlier than the pancreas, enters into the process of regulation of blood sugar. Removal of parotid SJ in adult dogs leads to insular insufficiency, the development of glycosuria, since secretions of SJ contain substances that delay the release of sugar. Salivary glands affect the preservation of subcutaneous fat. Removal of parotid SJ in rats causes a sharp drop in the calcium content in their tubular bones

The association of the activity of SJ with sex hormones was noted. There are cases when congenital absence of both SJ was combined with signs of sexual underdevelopment. The difference in incidence of SJ tumors in age groups indicates the effect of hormones. In tumor cells, both in nuclei and in the cytoplasm, receptors for estrogen and progesterone are found. All of the above data on the physiology and pathophysiology of SJ are coordinated by many authors with the incretory function of the latter, although no convincing information is given. Only a few researchers believe that the incremental function of the SJ is undoubted.

Often a person develops a condition called parotid hyperhidrosis or auriculotemporal syndrome after a trauma or resection of parotid SLE. A peculiar symptom-complex develops when, during food intake, when the taste agent irritates, the skin of the parotid-chewing area sharply turns red and there is a strong local sweating. The pathogenesis of this condition is completely unclear. It is assumed that it is based on the axon-reflex, carried out by the taste fibers of the glossopharyngeal nerve, passing through the anastomoses in the composition of the ear-temporal or facial nerves. Some researchers associate the development of this syndrome with the trauma of the ear-temporal nerve.

Observations on animals showed the presence of regenerative abilities of parotid cerebellum after resection of the organ, the severity of which depends on many factors. Thus, guinea pigs have a high regenerative capacity of parotid SJ with a significant restoration of function after resection. In cats and dogs, this ability is significantly reduced, and with repeated resection, the functional capacity is restored very slowly or not restored at all. It is assumed that after removal of the opposite parotid SL, the functional load increases, the regeneration of the resected gland accelerates and becomes more complete.

The SC tissue is very sensitive to penetrating radiation. Irradiation in small doses causes a temporary suppression of the gland function. Functional and morphological changes in the glandular tissue of the SC have been observed in experiments with irradiation of other areas of the body or general irradiation.

Practical observations show that any of the SJ can be removed without affecting the patient's life.