Inferior ganglion of glossopharyngeal nerve

The inferior ganglion of the glossopharyngeal nerve (petrous ganglion) is larger than the superior ganglion and is situated in a depression in the lower border of the petrous portion of the temporal bone which is named fossula petrosa.

It contains the bodies of general somatic sensory neurons (GSA fibers) that innervate the pharynx, tonsils, tongue, middle ear, auditory tube and the ear canal. It also contains the neurons that innervate the carotid sinus baroreceptors (which is a type of mechanoreceptors) and carotid body (chemoreceptors) through the Hering's nerve and the rami glomi carotici respectively. Rr. glomi carotici are the branches of vagus nerve but the origin of these fibers is glossopharyngeal nerve.