This is a closer view of one turn of the cochlear spiral.
The scala vestibuli and the scala tympani are labeled;
note that one is above and one below the scala media (labeled
here as SM). The scala media is the same as the cochlear duct. The scala vestibuli and scala tympani are bony labyrinth structures, filled with periplymph. The scala media/cochlear duct is membranous labyrinth; note that it's it's inside
the bony labyrinth. It is filled with endolymph. Also easily seen in this image are elements of the spiral ganglion, (SG). The spiral ganglion is a group of neuron cell bodies whose afferent fibers are attached to the "hair cells" of the organ of Corti (OC). This the ganglion receives input from the transducer cells of the ear and sends it to the brain via its efferent fibers. The organ of Corti, the actual site of sound transduction, lies enclosed within the scala media.
Inner ear; H&E stain, paraffin section, 100x