Scanning and transmission electron microscope studies on the organ of corti and stria vascularis in human fetal cochlear ducts.

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Abstract
The organ of Corti in human fetuses aged 5 and 7 mo., respectively, was observed with the scanning and transmission electron microscope (SEM and TEM). By SEM observation, bulbous cytoplasmic structures protruding from the apical surface of the outer and inner hair cells were observed, as was the case in previous SEM reports. By TEM observation, these structures were shown to be cytoplasmic projections from the so-called cuticular notch which, in adults, houses the basal body and is a site for synthesis of auditory stereocilia and a single kinocilium. The stria vascularis was examined only in the 5 mo. specimen. Cytoplasm of the differentiating marginal cells is characterized by the presence of thick walled tubular membranes. This tubular system may represent a particular site for secretion of some ions into the endolymph in the fetal condition.