Section 161: The chorda tympani (ct) is still visible in the middle ear spacemedial to the manubrium of the malleus (mm) and lateral to the long process of the incus (i). The tendon of the tensor tympani (ttt) hooks around a bony prominence (cochleariform process - cp) on the medial wall of the middle ear in order to run in a medial-lateral direction. The utricular macula (mu) is still visible along with the entrance into the vestibule of the non-ampullated portion of the lateral canal (lsc) and common crus (cc). Three turns of the cochlear spiral (c1, c2, a) are seen pointing anterolaterally, medial to the tensor tympani muscle (ttm). VIId - Tympanic segment of facial nerve.
Surgical perspective - At this level as well as that shown in sections 101 and 141, the facial nerve canal is part of the lateral wall of the vestibule. The medial wall of the vestibule is the lateral wall of the internal auditory meatus.