E, The petrous apex medial to the internal acoustic meatus has been removed to expose the petrous carotid. The lateral genu of the petrous carotid, located at the junction of the vertical and horizontal segments of the petrous carotid, is situated below and medial to the cochlea. The jugular bulb extends upward toward the vestibule and semicircular canals adjacent to the posterior meatal wall. The inferior petrosal sinus courses along the petroclival fissure and enters the petrosal part of the jugular foramen, and the sigmoid sinus descends in the sigmoid groove and enters the sigmoid part of the foramen. The glossopharyngeal, vagus, and accessory nerves pass through the central or intrajugular part of the foramen between the sigmoid and petrosal parts. F, Bone has been removed along the anterior margin of the meatal fundus to open the cochlea, and along the posterior margin to expose the vestibule. The jugular bulb extends upward toward the semicircular canals and vestibule. G, Enlarged view. The cochlear nerve penetrates the modiolus of the cochlea where its fibers are distributed to the turns of the cochlear duct. The basal turn of the cochlea communicates below the modiolus with the vestibule. H, Enlarged view of the vestibule and cochlea. The stapes has been removed from the oval window. The promontory in the medial wall of the tympanic cavity is located lateral to the basal turn of the cochlea. A silver fiber has been introduced into the superior canal, a red fiber into the lateral canal, and a blue fiber into the posterior canal. The ampullated ends are located at the bulbous ends of the three fibers. The common crus of the superior and posterior canals is located at the site where the tips of the blue and silver fibers overlap. The superior vestibular nerve passes to the ampullae of the superior and lateral canals. The singular branch of the inferior vestibular nerve innervates the posterior ampullae. A small black fiber has been introduced into the opening of the endolymphatic duct into the vestibule. (Images courtesy of AL Rhoton, Jr.)