Structure and Functions of the Sensory Hairs of the Inner Ear

The structure and relationships of the hairs of the cochlear and vestibular sensory cells have been investigated in fixed and fresh tissue by light, phase contrast, and electron microscopy. The cochlear hairs closely resemble the stereocilia of the vestibular cells, but there are differences in size, number, and arrangement between those of the inner and outer hair cells. In the cuticlefree region of the cell surface, a basal body is found, corresponding to the single kinocilium on each vestibular cell. The stiff cochlear stereocilia are regarded simply as levers, transmitting mechanical energy from the overlying tectorial membrane by way of the cuticular plate to the basal body. It seems unlikely that their bending as such has the importance generally ascribed to it. In view of the great functional significance of modified kinocilia in other sense organs, the basal body, like the vestibular kinocilium with its associated mitochondria, membranes, granules, appears to be the essential excitable structure o...