Which of the following are parts of the middle ear?

• A. Tympanic membrane; ossicles (malleus, incus, stapes)
• B. Cochlea; basilar membrane
• C. Semicircular canals; vestibule
• D. Eustachian tube; tympanic cavity

Answer: (A)

The middle ear is defined by its role in transferring sound energy from the eardrum to the inner ear through a chain of tiny bones. The tympanic membrane, or eardrum, marks the boundary between the outer and middle ears and vibrates in response to sound. Those vibrations are passed to the first bone, the malleus, then to the incus, and finally to the stapes. The stapes pushes on the oval window of the inner ear, delivering the mechanical energy into the cochlea. This lever-like system also helps adjust for the air-to-fluid impedance difference, making sound transmission more efficient. By contrast, the cochlea and basilar membrane reside in the inner ear and convert vibrations into neural signals; the semicircular canals and vestibule are involved in balance; and while the Eustachian tube connects to the middle-ear region to equalize pressure, it is not a primary structural component of the middle-ear cavity itself.