Section 200: Laterally, the external auditory meatus (EAM) or external ear canal is visible. The tympanic membrane (eardrum) forms the boundary between the external and middle (ME) ears. The manubrium (mm) of the malleus is attached to the medial surface of the eardrum. The long process of the incus (i) is located medial to the manubrium and lateral to the stapes (ac - anterior crus). Anteriorly, the middle ear narrows down to form the bony portion of the Eustachian (auditory) tube (et) which connects the middle ear to the nasopharynx. Running parallel to the auditory tube is the tensor tympani muscle (ttm) in its bony semicanal. The chorda tympani (ct) is nearing the back wall of the middle ear space. The footplate (fp) of the stapes which is held in the oval window by the annular ligament forms the boundary between the middle and inner ears. In this section both the auditory (i.e., cochlear - c) and vestibular (v) portions of the inner ear are visible. Note that the cochlea is anterior to the vestibular portion of the membranous labyrinth. In the cochlea, 5 cuts through the coiled cochlear duct are visible as it spirals around the modiolus (m). The vestibule (v) and the posterior semicircular canal (psc) are visible. The inferior division (id) of the VIII nerve (to cochlea and saccule) is visible in the internal auditory meatus (IAM). VIIf - Mastoid segment of facial nerve; ICA - Internal carotid artery.