Reissner’s membrane

Reissner's membrane, also known as the vestibular membrane, is a thin layer of cells that separates the scala vestibuli from the cochlear duct (scala media) within the cochlea of the inner ear. This membrane is crucial for maintaining the distinct fluid environments within the cochlea: the perilymph in the scala vestibuli and the endolymph in the cochlear duct.12

The Reissner membrane is composed of only two layers of flattened cells, forming a selective barrier that plays a role in the formation and ionic balance of the endolymph. It stretches from the inner margin of the limbus to the upper border of the stria vascularis. The unique ionic composition of endolymph, with a high concentration of potassium and low sodium, is maintained partly by the Reissner membrane's function.12