E, Enlarged view. The vestibule, into which the semicircular canals open, communicates below the meatal fundus with the cochlea. The vertical crest, often called Bill’s bar, separates the superior vestibular and facial nerves at the meatal fundus. The tendon of the tensor tympani makes a right-angle turn around the trochleariform process in the medial margin of the tympanic cavity to insert on the malleus. F, Enlarged view. The superior canal projects upward in the floor of the middle fossa. The lateral canal is situated above the tympanic segment of the facial nerve in the posteromedial part of the epitympanic area, and the posterior canal is located lateral to the posterior wall of the internal acoustic meatus. G, Bone has been removed below the greater petrosal nerve to expose the petrous carotid. The tensor tympani muscle above and the eustachian tube below are layered along the anterior surface of the petrous carotid. H, Enlarged view. Suture has been placed in the three semicircular canals. The anterior end of the superior and lateral canals and the lower end of the posterior canal are the site of the ampullae. The posterior end of the superior canal and the upper end of the posterior canal join to form a common crus. The facial and superior vestibular nerves have been removed to expose the cochlear and inferior vestibular nerves. The singular branch of the inferior vestibular nerve innervates the posterior ampullae. The superior vestibular nerve innervates the superior and lateral ampullae. (Images courtesy of AL Rhoton, Jr.)