The salivary glands consist of three paired major glands—parotid, submandibular, and sublingual—and the countless minor salivary glands found in almost every part of the oral cavity, except the gingiva and anterior regions of the hard palate. The secretion of saliva is essential for the normal function and health of the mouth, and disorders of salivary gland function predispose to oral disease. Functional disorders in salivary secretion may be associated with primary salivary gland disease but in other cases are a consequence of systemic factors, such as medications, endocrine disturbances, and neurological disease, which are discussed in Chapter 10. Developmental anomalies of the salivary glands are rare. Aplasia of one or more major glands and atresia of one or more major salivary gland ducts have been reported. Congenital aplasia of the parotid gland may be associated with other facial abnormalities, e.g. ectodermal dysplasia, mandibulofacial dysostosis, and hemifacial microsomia. Heterotopic salivary tissue has been reported from a variety of sites in the head and neck region, the most frequent being its inclusion at the angle, or within the body, of the mandible, called a Stafne bone cavity. It is usually an incidental radiological finding and appears as a round or oval, well-demarcated radiolucency between the premolar region and angle of the jaw, and is typically located beneath the inferior dental canal. The radiographic appearances are due to a saucer-shaped depression or concavity of varying depth on the lingual aspect of the mandible, which contains salivary tissue in continuity with the submandibular gland. Accessory parotid tissue within the cheek or masseter muscle is relatively common and is subject to the same diseases that may affect the main gland. Age changes can be detected in both major and minor salivary glands. Reduction in the weights of submandibular and parotid glands has been reported with increasing age, associated in the submandibular gland with an age-dependent reduction in flow rates. By contrast, several studies have demonstrated that there is no significant reduction in parotid flow rates in the elderly.
Nitric oxide in the control of submandibular gland function in the anaesthetized ferret
