osseous spiral lamina

From the spiral canal of the modiolus numerous canals pass outward through the osseous spiral lamina as far as its free edge.

The osseous spiral lamina consists of two plates of bone, and between these are the canals for the transmission of the filaments of the acoustic nerve.

The basilar membrane stretches from the tympanic lip of the osseous spiral lamina to the basilar crest and consists of two parts, an inner and an outer.

The osseous spiral lamina is a bony shelf or ledge which projects from the modiolus into the interior of the canal, and, like the canal, takes two-and-three-quarter turns around the modiolus.

In the lower part of the first turn a second bony lamina, the secondary spiral lamina, projects inward from the outer wall of the bony tube; it does not, however, reach the primary osseous spiral lamina, so that if viewed from the vestibule a narrow fissure, the vestibule fissure, is seen between them.