vestibular membrane

Reissner's membrane (vestibular membrane, vestibular wall) is a membrane inside the cochlea of the inner ear.

A set of membranes called the vestibular membrane and the basilar membrane separate the cochlear duct from the scala vestibule and the scala tympani.

The cochlear duct (or scala media) is an endolymph filled cavity inside the cochlea, located in between the scala tympani and the scala vestibuli, separated by the basilar membrane and Reissner's membrane (the vestibular membrane) respectively.

On the upper plate of that part of the lamina which is outside the vestibular membrane, the periosteum is thickened to form the limbus laminæ spiralis, this ends externally in a concavity, the sulcus spiralis internus, which represents, on section, the form of the letter C.