Right superior view of internal auditory canal, inner ear, and mastoid antrum. The roof of the internal auditory canal has been removed to reveal the facial nerve, nervus intermedius, geniculate ganglion, and greater superficial petrosal nerve. Posterior to the facial nerve within the canal is the superior vestibular nerve to the membranous labyrinth. Inferior to it is the cochlear nerve transmitting sensory impulses from the organ of Corti in the cochlea. Posterior to the cochlear nerve is the inferior vestibular nerve to the membranous labyrinth. The tegmen has been drilled out to reveal the epitympanum and aditus leading posteriorly to the mastoid antrum. Lateral to the tympanic cavity is the external auditory canal. Crossing the apex of the petrous portion of temporal bone is the trigeminal nerve, which expands as the trigeminal ganglion before giving rise to its three divisions. The motor root of the trigeminal nerve can be seen entering the foramen ovale where it fuses with its sensory root as the mandibular nerve. Posterolateral to the foramen ovale is the foramen spinosum and middle meningeal artery.  (Image courtesy of AL Rhoton, Jr.)