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the secretion and release of saliva into the oral cavity. Salivation is a reflex action in animals and man, arising in response to unconditioned and conditioned stimuli. It involves stimulation of the receptors of any of the centripetal nerves of the oral cavity or the pharynx—the lingual branches of the trigeminal or glossopharyngeal nerve or the branches of the superior laryngeal nerve—by food or by such objectionable substances as acids, alkalies, or sand. This stimulation results in simultaneous unconditioned salivation from the parotid and submaxillary glands. Salivation may also be a natural conditioned reflex arising from the sight or smell of food. When such conditioned stimuli as light and sound accompany the consumption of food, they eventually become signals evoking the conditioned reflex of salivation. This discovery enabled I. P. Pavlov to use the salivary glands as a model for the study of higher nervous activity in man and animals.
Excitation of the receptors of the oral cavity, eyes, ears, and olfactory organs is transmitted along the centripetal nerves to the center of salivation—the cerebral cortex, hypothalamus, and medulla oblongata. Here, the excitation is transmitted to the centrifugal parasympathetic nerves (the chorda tympani and the auriculotemporal nerves) and to the sympathetic nerves that proceed to the secretory portions of the salivary glands. Electrostimulation of the chorda tympani causes copious secretion of liquid saliva from the submaxillary glands, and stimulation of a sympathetic nerve causes limited secretion of viscid saliva rich in organic matter.
Salivation is also affected by hormones of the pituitary, thyroid, pancreas, and gonads. On an empty stomach, humans secrete saliva continuously at a basal rate of 0.24–0.9 milliliters per min. Dogs salivate every 1½ to 2 hr, and in ruminants the basal rate of secretion increases during ingestion and rumination. For purposes of examination, human saliva is collected from the salivary glands with a Krasnogorskii-Lashley capsule attached to the opening of the salivary duct. Fistulas are created in the salivary ducts of animals to study the secretion of animal saliva.
Salivation is affected by emotional excitement and by various pathological states. For example, excessive salivation (ptyalism) occurs in nausea, trigeminal neuralgia, and stomatitis, and decreased salivation (hypoptyalism) in some infectious diseases and diabetes.
REFERENCESPavlov, I. P. Lektsii o rabote glavnykh pishchevaritel’nykh zhelez, Poln. sobr. soch., 2nd ed., vol. 2, book 2. Moscow-Leningrad, 1951.
Abuladze, K. S. lzuchenie reflektornoi deiatel’nosti sliunnykh i sleznykh zhelez. Moscow, 1953.
Babkin, B. P. Sekretornyi mekhanizm pishchevaritel’nykh zhelez. Leningrad, 1960. (Translated from English).
Semenov, N. V. Biokhimicheskie komponenty i konstanty zhidkikh sredi tkanei cheloveka. Moscow, 1971.
V. D. SUKHODOLO