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تسجيل

Anatomy and physiology of saliva , The saliva glands

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  p166-167

2026-10-06

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Anatomy and physiology of saliva

The saliva glands

 The human saliva glands produce between 0.5 and 1.5 L of saliva daily. During resting conditions, most mixed saliva is supplied by the submandibular glands (70%) with a lesser amount (25%) from the parotid glands and the remaining (5%) from the sublingual and other minor glands (Baum 1993). During stimulation, the parotid saliva output increases to about half of the total. Saliva is composed of 99% water, 0.3% protein (largely amylase) and 0.3% mucins. The parotid gland produces mostly serous fluid. The submandibular and sublingual glands excrete both serous fluid and mucins. The saliva glands, like the liver, kidney and brain, are well supplied with arterial blood.

Saliva glands comprise two regions, the acinar region (which contains the cells capable of secretion) and the ductal region lined with water impermeable cells that carry the secretions to the outlets in the mouth (Turner 1993). Similarly, saliva formation occurs in two steps. Water and exocrine proteins are secreted by the secretory cells in the acinar region. The fluid collected in the acinar lumen is isotonic with plasma. As the fluid travels down the saliva ducts, sodium and chloride are reabsorbed, while potassium and bicarbonate are secreted. Therefore, when saliva moves rapidly through the ducts, less time is available for sodium reabsorption than other wise and the pH of the saliva is higher (Dawes and Jenkins 1964; see later). When the fluid reaches the mouth it is hypotonic to plasma. Saliva glands are activated by the autonomic nerves. Generally, sympathetic stimulation via noradrenaline (norepinephrine) causes low levels of fluid and high concentrations of protein, while parasympathetic stimulation via acetylcholine induces large amounts of fluid secretion.