Innervation The pharyngeal orifice of the eustachian tube is innervated by a branch from the otic ganglion, the sphenopalatine nerve, and the pharyngeal plexus.
The remainder of the tube receives its sensory innervation from the tympanic plexus and the pharyngeal plexus. The glossopharyngeal nerve probably plays the predominant role in tubal innervation. Sympathetic innervation of the tube depends on the sphenopalatine ganglion, the otic ganglion, paired glossopharyngeal nerves, the petrosal nerves, and the caroticotympanic nerve (Proctor, 1967). Mitchell (1954) suggested that the parasympathetic nerve supply is derived from the tympanic branch of the glossopharyngeal nerve. Nathanson and Jackson (1976) provided experimental evidence for secondary parasympathetic innervation via the Vidian nerve from the sphenopalatine ganglion. Innervation of the tensor veli palatini is from the ventromedial part 8 of the ipsilateral trigeminal motor nucleus through the trigeminal nerve (mandibular division), and the levator veli palatini muscle receives its innervation from the nucleus ambiguus through the vagus nerve .
Function The eustachian tube has at least three physiologic functions with respect to the middle ear:
(1) ventilation of the middle ear to equilibrate air pressure in the middle ear with atmospheric pressure;
(2) drainage and clearance into the nasopharynx of secretions produced within the middle ear; and
(3) protection from nasopharyngeal sound pressure and secretions.
(Swarts and Rood, et al 2005).