An electron microscopic study on the lining mucosa of developing rat vocal cords.

To explain the developmental process of epithelial cells of true vocal cords, larynges obtained from 42 fetal and 36 developing young rats were examined using scanning and transmission electron microscopies. Although the membranous portion was indistinguishable from the arytenoid portion in the prenatal stage, there was no squamous cell epithelium on the glottis. The lining epithelium of vocal cords in 15, 16, and 17 day fetal rats was composed of cuboidal and columnar cells which had a primary cilium. Immediately after birth the membranous portion of vocal cords became recognizable, and ciliated cells present on vocal cords retrogressed rapidly while nonciliated squamous cells grew and extended. Results of the present study show that epithelial cells of ciliated columnar type covering vocal cords change remarkably to nonciliated squamous cells between prenatal and postnatal stages.