Parasympathetic innervation of the salivary glands

The autonomic nervous system (ANS) is a mixed nervous system. There are two divisions of the ANS: the parasympathetic autonomous nervous system (PANS), and the sympathetic autonomic nervous system (SANS). The PANS plays a role in the conservation and homeostasis of bodily functions. The cells giving rise to parasympathetic fibers are situated at three different levels of the central nervous system: the midbrain, the medulla oblongata, and the sacral region of the spinal cord. The parasympathetic fibers leave the brain in the facial (VII CN), glossopharyngeal (IX CN), and vagus (X CN) nerves. The postganglionic parasympathetic fibers of the VII CN enter the sublingual and submanidublar glands and the minor salivary glands of the mucous membrane of the mouth, pharynx and nasopharynx, and those of the IX CN converge into the parotid gland. Parasympathetic postganglionic cholinergic nerve fibers supply cells of both the secretory end-piece and ducts and stimulate the rate of salivary secretion, inducing the formation of large amounts of a low-protein, serous saliva. Parasympathetic denervation of the major salivary glands leads to an immediate reduction of salivary secretion.