Basilar membrane

The osseous spiral lamina extends only part of the distance between the modiolus and the outer wall of the cochlea, while the basal lamina stretches from its free edge to the outer wall of the cochlea, and completes the roof of the scala tympani.

The basal lamina (basilar membrane) stretches from the tympanic lip of the osseous spiral lamina to the basal crest and consists of two parts, an inner and an outer. The inner is thin, and is named the zona arcuata: it supports the spiral organ of Corti. The outer is thicker and striated, and is termed the zona pectinata. The under surface of the membrane is covered by a layer of vascular connective tissue; one of the vessels in this tissue is somewhat larger than the rest, and is named the vas spirale; it lies below Corti’s tunnel.