Freeze-fracture study of the vestibular hair cell surface during development.

The ciliary arrangement and external surface of the vestibular receptor cell were studied in their immature stages. In the first stages, immature stereocilia are similar to the microvilli of the adjacent supporting cells. Later, when the cilia grow, a geometric arrangement of the stereocilia occurs, while the peripheral microvilli disappear. The size of the hair cell apex increases. The biggest and more bulbous cells correspond to type I hair cells, but in the newborn cat it is difficult to distinguish accurately type II flat hair cells from immature hair cells.