Saliva Essay

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Saliva The functions of saliva are reflected by its con- stituents. Mucins serve to lubricate the food, making it easier to swallow, and to keep the mouth moist to facilitate masticatory and speech-related movement. Saliva dissolves compounds in food, which is a prerequisite for taste buds stimulation and for dental and oral hygiene. Saliva has a low NaCl con- centration and is hypotonic, making it suitable for rinsing of the taste receptors (NaCl) while eating. Infants need saliva to seal the lips when suckling. Saliva also contains α-amylase, which starts the digestion of starches in the mouth, while immunoglobulin A and lysozyme are part of the immune defense system . The high HCO3– concentration in saliva results in a pH of around 7, which is opti- mal for α-amylase-catalyzed digestion. Swal- lowed saliva is also important for buffering the acidic gastric juices refluxed into the esophagus. The secretion of profuse amounts of saliva before vomiting also pre- vents gastric acid from damaging the enamel on the teeth. Saliva secretion is very dependent on the body water content. A low content re- sults in decreased saliva secretion—the mouth and throat become dry, thereby evoking the sensation of thirst. This is an important mecha- nism for maintaining the fluid balance Secretion rate. The rate of saliva secretion varies from 0.1 to 4 mL/min (10–250 μL/min per gram gland tissue), depending on the degree of stimulation. This adds up to about 0.5 to 1.5 L per day. At 0.5 mL/min, 95% of this rate is secreted by the parotid gland (se- rous saliva) and submandibular gland (mucin- rich saliva). The rest comes from the sublingual glands and glands in the buccal mucosa. Saliva secretion occurs in two steps: The acini (end pieces) produce primary saliva which has an electrolyte composition simi-

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