A diagram of the human ear. It is divided into the outer ear - A, middle ear - B, and inner ear - C. 1: ear trumpet or pinna, 2: outer ear passage with the drum that vibrates when sound waves hit it or the tympanum (3) across the inner ear, 4-5-6: the ear ossicles: hammer (malleus) anvil (incus) and stirrup (stapes) which transmit vibrations from the drum to the inner ear (they are also the smallest bones in the body), 7: the Eustachian tube, which connects to the mouth and through which air can indirectly enter, 8: largest chamber in the inner ear, called the utriculus, that has three semicircular canals, 9: the smallest chamber, called the sacculus, which is connected to the cochlea (10) which is the important hearing organ, 11: a "window" in the periotic bone, called the fenestra rotunda, 12: the endolymphatic duct.

Human Ear

A diagram of the human ear. It is divided into the outer ear - A, middle ear - B, and inner ear - C.…

"Transverse Section through Side Walls of Skull, showing the Inner Parts of the Ear. Co, concha or external ear, or pinna; EM, external auditory meatus; TyM, tympanic membrane; Inc, incus; Mall, malleus; ASC, PSC, ESC, anterior, posterior, and external semicircular canals; Coc, cochlea; Eu, Eustachian tube; IM, internal auditory meatus, through which the auditory nerve passes to the organ of hearing." -Whitney, 1911

Inner Ear

"Transverse Section through Side Walls of Skull, showing the Inner Parts of the Ear. Co, concha or external…

The membranous labyrinth is lodged within the bony labyrinth and has the same general form; it is, however, considerably smaller and is partly separated from the bony walls by a quantity of fluid, the perilymph. In certain places, it is fixed to the walls of the cavity. The membranous labyrinth contains fluid, the endolymph, and on its walls the ramifications of the acoustic nerve are distributed. Within the osseous vestibule, the membranous labyrinth does not quite preserve the form of the bony cavity, but consists of two membranous sacs, the utricle, and the saccule. The membranous labyrinth is also the location for the receptor cells found in the inner ear.

Membranous Labyrinth

The membranous labyrinth is lodged within the bony labyrinth and has the same general form; it is, however,…