Embryogenesis of the mammalian inner ear. III. Formation of the tectorial membrane of the CBA/CBA mouse in vivo and in vitro.

The development of the tectorial membrane in the basal coil of the cochlea has started already in the 15th gestational day inner ear and has reached a considerable thickness and maturation at birth. The development of the tectorial membrane occurs synchronously in in vivo labyrinths and the in vitro material cultured to an age corresponding to birth. At least during this part of the development the formation of the tectorial membrane is independent of the specific composition of endolymph. In the in vivo material a secretory maximum was reached on the 18th gestational day, whereafter the secretory activity was low, especially after birth. In the in vitro specimens, however, a rather constant secretion of material occurred also post partum, which indicates a lack of control mechanisms during in vitro conditions. A complete maturation of the tectorial membrane did not occur in vitro. When passing the point of time corresponding to birth, in the in vitro inner ear explants the gross structure of the tectorial membrane is only slightly changed. In vivo a mature configuration of the tectorial membrane is observed on the 14th DAB (day after birth).