Right posterolateral view of epitympanum and mesotympanum following mastoidectomy. The auricle is located at the top of the image (anterior); superior is toward the left border. The mastoid process has been drilled out to reveal the floor of the external auditory canal and the facial canal descending in the posterior wall of the mesotympanum. The epitympanum contains the head of the malleus and body and short crus of the incus. The fossa incudis is a small depression in the posteroinferior part of the epitympanum that contains the short crus of the incus and its posterior ligament. The long crus of the incus articulates with the head of the stapes in the mesotympanum, whose base attaches to the oval window, The facial recess is a small recess in the posterior wall of the mesotympanum and is bounded by the mastoid portion of the facial nerve posteriorly, the chorda tympani anteriorly, and the fossa incudis superiorly. The posterior buttress is a bony bridge between the floor of the external auditory canal and the upper posterior wall of the facial canal lateral to the facial nerve. (Image courtesy of AL Rhoton, Jr.)