Cochlea of the human fetus: A scanning electron microscope study.

Abstract

To study the developmental microanatomy of the cochlea, fine structures of the human fetal cochlea were observed by scanning electron microscopy. The temporal bones of fetuses were removed and the membranous portions of the cochleas were prepared for observation. In a 14-wk 6-day-old fetus, the hair cells were arranged mainly in 4 rows. The sensory hairs differed in appearance from those in the adults. The innermost or 1st row hair cells corresponded to the inner hair cells and revealed certain characteristic structures. From the 2nd to the 3rd or outermost row, a rather uniform hair pattern with a bud-like appearance was noted. Neither W nor V letter formation of sensory hairs was found. One strong kinocilium was identified with its thick base; it was located lateral to the outermost stereocilia. With older fetuses, 22-wk 2-days and 24-wk 0-day of age, the hair patterns closely resembled those of the adult with the exception of the presence of a short kinocolium on the outer hair cells and a slim kinocilium on the inner hair cells. Structures including the sensory hairs and their attachment to the tectorial membrane, the Reissner''s membrane and the stria vascularis essentially complete their morphological development in 6 mo. after gestation.