oval window

Meaning: The oval window is a membrane-covered opening between the middle ear and the fluid-filled cochlea of the inner ear. The stapes, the last of the three ossicles, pushes on it and sets the cochlear fluid moving. The eardrum has a much larger area than the oval window, and the ossicles act as levers, so force is concentrated on a small area and pressure rises (P = F/A). This helps move sound from air into fluid, which is harder to vibrate.

On the MCAT: Expect to trace the path of sound: pinna → auditory canal → tympanic membrane → malleus → incus → stapes → oval window → cochlear fluid → basilar membrane → hair cells → auditory nerve. A passage may describe stiff or damaged ossicles and ask you to separate hearing loss from poor conduction of vibrations from hearing loss due to hair cell or nerve damage.

Common confusion: The oval window does not transduce sound into neural signals; the hair cells on the basilar membrane do. It is also not the round window, which bulges outward to relieve pressure as the cochlear fluid is displaced, and it is not the eardrum (tympanic membrane), which is the larger membrane at the start of the middle ear.