The labyrinth is a complex system of chambers and tubes in the inner ear. There are actually two labyrinths in each ear: the osseous—or bony—labyrinth and the membranous labyrinth. The three regions of the bony labyrinth are the vestibule, the cochlea, and the semicircular canals. There are two membranous sacs within the vestibule, the saccule and utricle, which contain receptors that respond to linear acceleration (e.g., the pull of gravity, acceleration in a vehicle, and changes in head position).