Final answer:
The internal ear structures, including the cochlea and vestibule in the inner ear, function in both hearing and equilibrium. While the external and middle ear are involved in hearing only, the inner ear assists in balance.
Step-by-step explanation:
The external and middle ear are designed primarily for the reception and transmission of sound, generally referred to as hearing or audition. The external ear is comprised of the auricle, ear canal, and tympanic membrane, which funnel sound waves toward the middle ear. The middle ear contains three bones known as the ossicles the malleus, incus, and stapes, which amplify and transmit vibrations to the inner ear.
The inner ear, however, serves a dual function. It houses the cochlea, essential for hearing reception, but it also contains the vestibule and semicircular canals, which are responsible for maintaining equilibrium or balance. This balance function of the inner ear is also identified as the vestibular system.