![]() When stimulated, the parotids provide most of the saliva and flow can increase by up to fivefold. In the resting state 70% of saliva is secreted by the submandibular and sublingual glands. Saliva may be secreted in the absence of exogenous stimuli, then referred to as the resting or unstimulated salivary flow. 6 A dry mouth is a common experience where there is fear. ![]() 5 Autonomic nerves also have an important role in both gland development and function. The flow of saliva is enhanced by sympathetic innervation, which promotes contraction of muscle fibers around the salivary ducts. The cranial nerve VII provides control of the submandibular, sublingual, and minor glands, whereas the cranial nerve IX controls the parotid glands. The efferent part of the reflex is mainly parasympathetic. Impulses affecting secretion depending on the emotional state are carried by afferent cranial nerves V, VII, IX, and X to the CNS salivary nuclei (salivation center) in the medulla oblongata. 4 Olfaction, mental processes, and stretch of the stomach are weak stimuli. The afferent arm is mainly activated by stimulation of chemoreceptors (located in the taste buds) and mechanoreceptors (located in the periodontal ligament). Salivary secretion and maintenance of a film of saliva on oral surfaces is dependent upon nerve-mediated, reflex salivary gland secretion mainly stimulated by taste. ![]() The composition of saliva is modified, depending on factors such as secreted amount, circadian rhythm, duration and nature of stimuli, diet, and medication intake, among others.ĭespite this heterogeneous composition, from the functional point of view saliva has to be considered as a unique biological fluid, and not as the sum of its biochemical components. 1 Cellular elements such as epithelial cells, leucocytes and various hormones, and vitamins have also been detected. Salivary constituents can be grouped into proteins (e.g., amylase and lysozyme), organic molecules (e.g., urea, lipids, and glucose mainly), and electrolytes (e.g., sodium, calcium, chlorine, and phosphates). In the mouth saliva is a colorless, odorless, tasteless, watery liquid containing 99% water and 1% organic and inorganic substances and dissolved gases, mainly oxygen and carbon dioxide. Saliva is produced by both major (parotid and submandibular and sublingual) and minor (located in the mouth) glands, with different constituents and properties between the two groups.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |