![]() ![]() Post-synaptic neurons in the otic ganglion travel along the auriculotemporal nerve to distribute to the parotid gland. Along the superior aspect of the tympanic cavity, the tympanic plexus converges to form the lesser petrosal nerve which provides preganglionic parasympathetic innervation to the otic ganglion. The tympanic nerve (nerve of Jacobson) arises from the inferior ganglion, traverses the tympanic canaliculus and provides innervation to the middle ear cavity, mastoid air cells and auditory tube via the tympanic plexus. Axons reaching the rostral SN convey gustatory sense from the posterior one-third of the tongue those reaching more caudal SN relay visceral sensory information from the pharynx, middle ear, oral cavity and carotid sinus/body. Axons reaching the STN convey pain and thermal sense from the external ear. These primary sensory neurons project to the spinal trigeminal nucleus (STN) or solitary nuclei (SN). ![]() Together, these sensory ganglia include pseudounipolar cell bodies that provide general somatic, visceral and special visceral innervation across the territory of CN IX. There are two sensory ganglia associated with CN IX: the superior and inferior (petrosal). The ISN provides preganglionic parasympathetic innervation to scattered ganglion cells in the tympanic cavity and otic ganglion. The NA includes lower motor neurons that provide innervation to the stylopharyngeus muscle. A focal weakness or deficiency in this area of the pharyngeal wall is termed a Killian dehiscence and can produce a pulsion-pseudodiverticulum, known as a pharyngeal diverticulum or pouch (Zenker diverticulum).Efferent axons in CN IX are derived from the nucleus ambiguous (NA) and the inferior salivatory nucleus (ISN). The area of the pharyngeal wall at the junction between the thyropharyngeus and the cricopharyngeus is a potentially weak area.
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