Petrosal fossula

The petrosal fossula refers to a small depression on the inferior surface of the petrous temporal bone. It is located in the ridge between the jugular fossa and external opening of the carotid canal. The petrosal fossula houses the inferior (petrous) ganglion of the glossopharyngeal nerve (origin of Jacobson nerve) and superiorly gives rise to the (inferior) tympanic canaliculus . The structure may be considered part of pars nervosa of the jugular foramen .

The petrosal fossula is distinct from and located below the external opening of the cochlear aqueduct , which in turn arises from the pyramidal fossa, the part of the roof of the jugular foramen that covers the pars nervosa .