Three dimensional measurements of hair cell stereocilia of Corti's organ in guinea pigs.

The surface of the organ of Corti of guinea pigs was examined with a scanning electron microscope. The sensory cilia showed an orderly gradation in height and diameter along the length of the cochlea. The cilia were taller and thicker at the apex and shorter and thinner at the base. The number of cilia on the outer hair cells increased with the distance from the apex of the cochlea. However, there was no significant change in the number of inner hair cells. The angle of the arrangement of the sensory cilia was wider at the base and narrower at the apex. These morphological findings suggest that there maybe an additional fine frequency analysis system built into the organ of Corti in addition to the basilar membrane.