Inner ear, also called labyrinth of the ear, part of the ear that contains organs of the senses of hearing and equilibrium. The bony labyrinth, a cavity in the temporal bone, is divided into three sections: the vestibule, the semicircular canals, and the cochlea. Within the bony labyrinth is a membranous labyrinth, which is also divided into three parts: the semicircular ducts; two saclike structures, the saccule and utricle, located in the vestibule; and the cochlear duct, which is the only part of the inner ear involved in hearing. The cochlear duct forms a shelf across the cochlea dividing it into two sections, the scala vestibuli and the scala tympani. The entire inner ear is bathed in a cushioning fluid, called the endolymph when it lies within the membranous labyrinth and the perilymph when it separates the bony and membranous labyrinths.