The Smallest Bone

The stapes is the smallest bone in the human skeleton, measuring about 3 mm. It is the last of the three auditory ossicles in the middle ear: the malleus transfers eardrum motion to the incus, and the stapes moves at the oval window to transmit vibrations into the fluid of the inner-ear cochlea. The ossicular chain helps couple sound from air to the fluid-filled inner ear; the resulting mechanical motion ultimately triggers hair-cell signals carried by the auditory nerve.