Basal turn of cochlea

The basal turn of the cochlea is defined as the first, most proximal 360-degree spiral segment of the cochlear duct, beginning at the round window and extending anteriorly and inferiorly. It is located closest to the middle ear cavity and the stapes footplate, and is anatomically distinguished by its larger diameter compared to the more apical turns.

The basal turn is functionally significant as it houses the regions of the basilar membrane that are maximally responsive to high-frequency sounds, due to the tonotopic organization of the cochlea.