Left lateral view of tympanic cavity and bony labyrinth following mastoidectomy and posterior tympanotomy. For orientation, the top border of the image is anterior; the right border is superior. The profiles of the semicircular canals (lateral, superior, posterior) are in view. The tympanic membrane has been removed to expose the mesotympanum, the main compartment of the tympanic cavity between the tympanic membrane and the oval window that contains the ossicular chain. The head of the malleus and body and short process of the incus lie in the epitympanum portion of the middle ear cavity. Bone has been removed around the mastoid portion of the facial nerve and its chorda tympani branch. The chorda tympani arches across the tympanic cavity from posterior to anterior medial to the neck of the malleus between it and the incus bone. The facial recess, a small triangular space bounded by the fossa incudis superiorly, the facial nerve posteriorly, and the chorda tympani anteriorly, is surgically traversed to perform cochlear implantation surgery. (Image courtesy of AL Rhoton, Jr.)