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How do middle-ear ossicles help transfer sound from air to the inner ear?
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Mechanoreception
In human skin, specialized nerve endings known as Meissner's corpuscles (or tactile corpuscles) are sensitive to touch. They are one of several different types of mechanoreceptors found in human skin.
The middle-ear ossicles—the malleus, incus, and stapes—function as an impedance-matching transformer to overcome the resistance encountered when sound moves from air into the fluid-filled inner ear. Without this mechanism, most sound energy would be reflected away from the fluid, resulting in significant hearing loss.1
The ossicular chain achieves this through two primary mechanical actions:
- Area Reduction: Sound energy vibrating the relatively large tympanic membrane is concentrated onto the much smaller area of the stapes footplate. This concentration increases the pressure exerted on the inner ear fluids at least 13-fold.1
- Leverage: The malleus and incus form a lever system that provides additional mechanical advantage, further amplifying the force.1
Together, these features increase the total pressure at the oval window at least 17-fold, allowing airborne vibrations to effectively displace the cochlear fluids and stimulate the hearing mechanism.12