What structure sections off the three tapering tubes of the cochlea?

The correct answer is the basilar membrane. The basilar membrane is a critical structure within the cochlea that separates the scala tympani and scala vestibuli. It plays a fundamental role in the auditory process, as it supports the organ of Corti, where hair cells are located. These hair cells transduce sound vibrations into neural signals, which are sent to the brain for interpretation.

The configuration of the cochlea consists of three fluid-filled chambers: the scala vestibuli, the scala media (or cochlear duct), and the scala tympani. The basilar membrane allows for the differentiation of frequencies of sound due to its varying stiffness along its length, leading to specific areas vibrating in response to certain sound frequencies. This structural specialization is essential for effective sound perception.

In contrast, structures such as the cochlear duct itself is a chamber rather than a separator, while the oval and round windows serve as membrane-covered openings that transmit sound vibrations from the middle ear to the cochlea but do not function as separators of the cochlear tubes.