The human ear has three important regions— external, middle, and internal. The external ear consists of the cartilaginous auricle and the auditory canal, which directs the sound waves to the eardrum or tympanic membrane. The eardrum is a thin, transparent tissue membrane that vibrates to the incoming sound. It separates the middle ear from the external ear. The middle ear is an air-filled space that is connected to the nasopharynx by the auditory tube. During swallowing or yawning, the tube opens briefly to equalize air pressure. The middle ear includes three auditory ossicles—the malleus, incus, and stapes. These ossicles transmit vibrations from the eardrum to the fluid-filled internal ear. The vestibule is the central oval-shaped structure in the internal ear. Projecting from the vestibule are the three semicircular canals. The vestibule and semicircular canals detect changes in the head position and maintain body equilibrium. Anterior to the vestibule is the cochlea, a spiral structure resembling a snail shell. It houses the organ of Corti, which contains the receptors for hearing.