Fundic view of right internal auditory canal and inner ear. The petrous bone has been drilled to visualize the three parts of the bony labyrinth: cochlea, vestibule, and semicircular canals. The ampullae and ducts of the superior, lateral, and posterior semicircular canals are indicated by the colored pins and wires. The oval window is the lateral boundary of the vestibule, while the cochlea and semicircular canals form its anterior and posterior boundaries, respectively. The facial and vestibulocochlear nerves separate in the fundus of the internal auditory canal. The facial nerve is separated from the superior vestibular nerve by the vertical crest or Bill's bar, with the facial nerve being the anterior of the two nerves here. The superior vestibular nerve conveys sensory fibers from the hair cells of the lateral and superior semicircular canals and the utricle. The transverse crest separates these superior compartment nerves from the inferior compartment nerves consisting of the cochlear (anteriorly) and inferior vestibular (posteriorly) nerves. The cochlear or auditory nerve conveys sensory fibers from hair cells in the organ of Corti, while the inferior vestibular nerve conveys sensory information from the saccule. The singular nerve is a branch of the inferior vestibular that carries sensory fibers from the ampulla of the posterior semicircular canal. (Image courtesy of AL Rhoton, Jr.)