Superior Salivatory Nucleus

The Five Senses and Beyond: The Encyclopedia of Perception - Jennifer L. Hellier 2017

Superior Salivatory Nucleus

The superior salivatory nucleus is a structure associated with cranial nerve VII or the facial nerve that innervates the submandibular and sublingual salivary glands and is important in the secretion of saliva for digestion. It works together with the inferior salivatory nucleus to allow for full function of the parotid gland. The superior salivatory nucleus has portions that are also part of the lacrimal nucleus, which innervate the lacrimal and mucosal glands.

Basic Salivary Gland Anatomy

The major salivary glands in humans are responsible for the synthesis and secretion of saliva, a product that helps with the initial steps of digestion of food. There are three major paired salivary glands that make up this system: (1) the sublingual glands, which are the smallest of the major salivary glands and are located under the tongue, and which secrete saliva into the floor of the mouth through the duct of Rivinus; (2) the submandibular glands, which are somewhat larger than the sublingual glands and are located under the mandible (or jaw bone) and also secrete saliva into the floor of the mouth; and (3) the parotid glands, which are the largest of the salivary glands and are located just below and behind the ear. The parotid glands are the glands that become inflamed when a person has the mumps. Saliva is secreted into the mouth from the parotid gland through the Stensen duct (or parotid duct). Sensory and autonomic nerves including cranial nerve IX or the glossopharyngeal nerve, which is composed in part by the inferior and superior salivatory nuclei, regulate the parotid gland.

Autonomic Innervation of the Submandibular and Sublingual Glands

The peripheral nervous system in humans is composed of the somatic nervous system, which sends nerves to many of the muscles that we control voluntarily and exits the central nervous system from the spinal cord, and the autonomic nervous system, which regulates the organs and structures of the body that we do not voluntarily control. In the autonomic nervous system there are two neurons that are important to the function of this system: (1) the preganglionic neuron, which passes from the spinal cord or brain to a peripheral autonomic “ganglion,” where a synapse is formed with the second neuron known as the (2) postganglionic neuron, which passes from the autonomic ganglion after forming a synapse with the preganglionic neuron to the organ or other structure innervated by the nerve.

Cranial nerve VII is responsible for the innervation of the submandibular and sublingual glands. It is composed of two neurons, both a preganglionic and a postganglionic neuron. The first neurons, or the preganglionic neurons, are distributed partly via the chorda tympani and lingual nerves to the submandibular ganglion. The postganglionic fibers then travel to the submandibular gland and sublingual gland to innervate the secretory cells. When these secretory cells are activated they release saliva, which is required for early digestion in the mouth.

Autonomic Innervation of the Lacrimal and Mucosal Glands

Some of the preganglionic fibers of the superior salivatory nucleus travel with the greater petrosal nerve through the pterygoid canal. These fibers stimulate the pterygopalatine ganglion, which has postganglionic fibers that travel to the lacrimal and mucosal glands. Activation of these postganglionic fibers produces tears from the lacrimal gland in the eye as well as mucus from the mucosal glands in the nose, palate, and pharynx.

Pathology of the Superior Salivatory Nucleus

The superior salivatory and its adjoining lacrimal nuclei are dispersed and lie just medial of the motor portion of the facial nucleus. Thus, damage to the facial nucleus generally results in damage to the superior salivatory nucleus. This would result in the lack of ability to produce saliva from the submandibular and sublingual glands, tears from the eye, and mucus on the same side of the lesion. This is often seen in Bell’s palsy, which may be caused by edema (swelling) and inflammation of the facial nerve. It is characterized by unilateral (one side) and temporary weakness or total paralysis of the facial nerve

Jennifer L. Hellier and Charles A. Ferguson

See also: Autonomic Nervous System; Bell’s Palsy; Chorda Tympani Nerve; Facial Nerve; Inferior Salivatory Nucleus; Taste Bud; Taste System

Further Reading

Holsinger, F. Christopher, & Dana T. Bui. (2007). Anatomy, function, and evaluation of the salivary glands. In Eugene N. Myers and Robert L. Ferris (Eds.), Salivary gland disorders (pp. 1—16). Berlin and Heidelberg: Springer-Verlag.

Kiernan, John A. (2005). Barr’s The human nervous system: An anatomical viewpoint (p. 150). Baltimore, MD: Lippincott Williams & Wilkins.