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(1) The innermost auditory ossicle of the middle ear in man and most other mammals. Together with the malleus (hammer) and incus (anvil), the stapes participates in the transmission of sound into the inner ear. The bony plate at the base of the stapes is situated in the oval window of the vestibule of the cochlea, which is found on the inner wall of the tympanic cavity. Two thin crura depart from the base of the stapes and unite to form the stapedial arch. The head of the stapes, which articulates with the incus, is found at the apex of the arch.
In many mammals the stapes resembles a stirrup, hence the common name of the bone.
(2) The only auditory ossicle in most amphibians and in all reptiles and birds. The term “columella” is also used in reference to the ossicle.