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Left Lateral View of Mesotympanum, Epitympanum, and Semicircular Canals

Surgical Correlation


Left lateral view of mesotympanum, epitympanum, and semicircular canals. The jugular bulb can be seen in the lower part of this image inferior to the posterior semicircular canal. The facial canal contains the facial nerve and it's tympanic and mastoid segments.  The tympanic segment of the nerve passes inferior to the lateral semicircular canal. Inferior to this is the oval window and the base of the stapes. Along the posterior wall of the mesotympanum is the pyramidal eminence containing the stapedius muscle. Its tendon emerges from the summit of this eminence to attach to the neck of the stapes. Inferior to the eminence is the round window. Just beyond the pyramidal eminence the facial nerve continues as the mastoid segment, which gives rise to the stapedial nerve and chorda tympani, the latter of which arches forward in the tympanic cavity between the handle of malleus and long process of incus. The incus and it's short limb (located in the fossa incudis) are seen in the epitympanum that opens posteriorly into the mastoid antrum. The facial recess, a small space on the posterior wall of the mesotympanum lateral to the pyramidal eminence, is located immediately anterior to the upper portion of the mastoid segment of the facial nerve.  (Image courtesy of AL Rhoton, Jr.)