The enigmatic root cell - Emerging roles contributing to fluid homeostasis within the cochlear outer sulcus

► Outer sulcus root cells have morphological and functional features that show tonotopic variation. ► In low frequency coding regions they contact endolymph and likely absorb cations. ► In high frequency regions the basolateral membrane is specialized for K+ recirculation. ► Root cells may contribute to the cochlear response to stress. ► Root cell function may be adversely affected by numerous deafness gene mutations.