All sensory hair cells of the inner ear exist in extracellular fluid, but in some areas the fluid has the characteristics of intracellular fluid, as far as concentrations of K+ and Na+ are concerned. The membranous labyrinth contains the intracellular fluid-like endolymph, and is surrounded by a distinct extracellular fluid, the perilymph. The sensory hair cells of the cochlea are surrounded by extracellular fluid called cortilymph in a separate compartment. Excessive accumulation or leakage of any of these fluids may affect the functions of the whole or partial inner ear.