=== Endolymph and Perilymph ===

The membranous labyrinth is filled with endolymph and is surrounded by perilymph. Endolymph is a unique fluid, with high K+ concentration and very low Na+ concentration. This endolymph provides the proper ionic environment for hair cell function. Endolymph is secreted by cells of the stria vascularis, along the scala media of the cochlea.