The cochlear duct (lat .: cochlear duct ) or scala media (lat .: middle staircase) is the name given to the middle of the three ducts of the cochlea in the inner ear .
The cochlear duct is at the top through the Reissner membrane ( Membrana vestibularis Reissner) from the Scala vestibuli (lat .: atrial staircase), at the bottom by the lamina spiralis ossea (lat .: spiral bone sheet) or its continuation outwards, the limbus spiralis ( lat .: spiral edge) and the basilar membrane separated from the scala tympani (lat .: tympanic staircase). Scala vestibuli and scala tympani are connected to each other at the apex via the helicotrema and filled with perilymph . The cochlear duct is filled with endolymph and ends blindly at the tip of the cochlea. However, it is connected to the sacculus by a thin duct ( ductus reuniens ) and thus further via the ductus endolymphaticus to the saccus endolymphaticus , a blind sac between two sheets of the hard meninges on the posterior wall of the temporal bone.
The cochlear duct contains the organ of Corti with the hair cells and the tectorial membrane , a thin membrane that lies over the organ of Corti and ends free outside the outer hair cells.