middle ear

Meaning: The middle ear is the air-filled chamber between the eardrum (tympanic membrane) and the cochlea's oval window. Its three ossicles, in order from the eardrum, are the malleus, incus, and stapes. They carry eardrum vibrations to the oval window, which moves the cochlear fluid. Sound passing from air to fluid would mostly reflect, so the middle ear amplifies pressure: the large eardrum focuses force on the small oval window, and the ossicles add lever action. The Eustachian tube equalizes pressure with the throat.

Equation: P = F/A, where P is pressure (Pa), F is force (N), and A is area (m²).

On the MCAT: Expect questions that order the sound pathway: eardrum, malleus, incus, stapes, oval window, cochlea, hair cells, auditory nerve, thalamus, temporal lobe cortex. Others sort structures into outer, middle, or inner ear, or link damage to the type of hearing loss: eardrum or ossicle problems cause conduction loss, while hair cell or nerve damage causes sensorineural loss.

Common confusion: The middle ear does not turn sound into neural signals. That transduction is done by hair cells on the basilar membrane in the cochlea, which is inner ear. The semicircular canals (balance) are also inner ear.