Outer–Middle–Inner Ear and Central Hearing System Anatomy

Sound waves emitted by the surrounding environment are received and transmitted via the outer ear, composed of the pinna, external auditory canal, and tympanic membrane (TM). The ossicles—the malleus, incus, and stapes—are bones that transport vibrations from the tympanic membrane to the inner ear. The middle ear is an air-filled region that contains these bones. The malleus sends vibrations via the incus to the stapes, which then contacts the cochlear oval window. The cochlea, semicircular canals, utricle, and saccule comprise the inner ear, housed within the bony labyrinth of the temporal bone. Within the bony labyrinth, these organs form the membrane labyrinth, with perilymph as the sole divider. Endolymph, a fluid contained in the membranous labyrinth, is essential for stimulating hair cells that transmit vestibular signals and sound.