Interior view of the petrous temporal bone and inner ear. The petrous temporal bone has been opened to reveal the petrous portion of the internal carotid artery and the inner ear. A sympathetic plexus surrounds the internal carotid artery as it courses intracranially. The pre-geniculate facial nerve runs between the semicircular canals and the cochlea. The greater superficial petrosal nerve courses anteriorly from the genu along the middle cranial fossa floor and under cranial nerve V3. The tympanic segment of the facial nerve is the first segment after the geniculate ganglion until the pyramidal eminence, a bony conical projection within the middle ear, where the transition is made to the mastoid segment of the facial nerve. (Image courtesy of AL Rhoton, Jr.)