Early aspects of human cochlea development and tectorial membrane histogenesis.

Several human embryos and foetuses cochlea from the first half of pregnancy were studied by light, transmission and scanning electron microscopy. Cochlea development in man is the result of three coexisting processes: First, coiling and maturation of the cartilaginous otic capsule. Second, resorption of the periodic mesenchymal reticulum with the appearance of the labyrinthine fluids. Third, differentiation of the sensory epithelium. Tectorial membrane morphogenesis is closely related to the apocrine secretory activity of the greater and lesser epithelial ridges in the 50 mm c.r.l. specimen. In the 70, 110 and 120 mm c.r.l. specimens the secretory activity rests on the interdental cells of the spiral limbus, the undifferentiated cells of Corti's primordium and in the most external cells of the lesser epithelial ridge.