Saliva

Saliva is a clear, watery secretion produced by the salivary glands in the oral cavity. The major glands are the parotid, submandibular, and sublingual glands, with minor glands contributing as well. Secretion is regulated by the autonomic nervous system and varies with stimulation, sleep, and health. At rest, saliva flow is relatively low; during meals it increases, yielding an average daily production of about 0.5 to 1.5 liters.

Composition is complex. Saliva is about 99% water, with electrolytes, mucus, and a range of proteins. Digestive enzymes include salivary amylase, which starts starch digestion, and, in some individuals, lingual lipase. Antimicrobial components include lysozyme, lactoferrin, peroxidases, and secretory IgA. Minerals such as calcium and phosphate support remineralization of enamel.

Functions include lubrication of the mouth, protection of mucosa, initiation of digestion, buffering of acids, cleansing, taste facilitation, and antimicrobial defense. The mineral content and pH help stabilize the oral environment and promote tooth remineralization.

Clinical relevance: reduced saliva flow, or xerostomia, can result from aging, medications, Sjögren's syndrome, or radiation therapy, increasing the risk of dental caries, infections, and mucosal discomfort. Saliva plays an important role in oral health and comfort, and its properties are often considered in dental and medical assessments.