The cochlear (round window) and vestibular (oval window) windows connect the middle ear to the inner ear. The cochlear duct (scala media) is bounded superiorly by Reissner's membrane and inferiorly by the basilar membrane. High-frequency sounds are transduced at which part of the basilar membrane?
- A Base of the cochlea (narrowest, stiffest part of the basilar membrane) ✓
- B Apex of the cochlea (widest, most flexible part of the basilar membrane)
- C Middle turn of the cochlea
- D Helicotrema
Correct answer: A. Base of the cochlea (narrowest, stiffest part of the basilar membrane)
Explanation
The basilar membrane varies along its length: it is narrow and stiff at the base (near the oval window) and wide and flexible at the apex. According to the place theory of hearing, high-frequency sounds maximally deflect the stiff basal portion, while low-frequency sounds travel to the flexible apex. This tonotopic organisation is preserved from the cochlea all the way to the primary auditory cortex. Noise-induced hearing loss typically affects the basal turn (4000 Hz region) first.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.