In the ear, which structure separates the outer ear from the middle ear?

In the ear, which structure separates the outer ear from the middle ear?

• A. Cochlea
• B. Eustachian tube
• C. Tympanic membrane
• D. Semicircular canals

Answer: (C)

The boundary between the outer ear and the middle ear is the tympanic membrane, also known as the eardrum. This thin, cone-shaped membrane sits at the end of the external auditory canal and vibrates when struck by sound waves, transferring those vibrations to the auditory ossicles in the middle ear. Its placement specifically separates the external auditory space from the air-filled middle ear. The Eustachian tube helps ventilate the middle ear but doesn’t form the boundary, while the cochlea and semicircular canals are in the inner ear and related to hearing and balance, not the external–middle ear separation.

The boundary between the outer ear and the middle ear is the tympanic membrane, also known as the eardrum. This thin, cone-shaped membrane sits at the end of the external auditory canal and vibrates when struck by sound waves, transferring those vibrations to the auditory ossicles in the middle ear. Its placement specifically separates the external auditory space from the air-filled middle ear. The Eustachian tube helps ventilate the middle ear but doesn’t form the boundary, while the cochlea and semicircular canals are in the inner ear and related to hearing and balance, not the external–middle ear separation.