Cochlear Duct

00:00 Here is a section. On the left-hand side, low magnification section through the organ of Corti, and on the right-hand side, a high magnification. It shows the organ of Corti projecting into the endolymph of the cochlea duct. There's the organ of Corti there. It has a component, or the endolymph is contained within the scala media, you see labelled there. That's the endolymph component of the cochlea duct. There's a spiral ganglion there. The spiral ganglion is the bipolar neurons that send dendritic branches to the hair cells in the organ of Corti. And then the other component of those ganglion cells sends information through the cochlea nerve back into the central nervous system. So that spiral ganglion sits in the bone adjacent to each coil of the cochlea duct. The bone is the modiolus that I've explained earlier. There is two compartments of perilymph, the scala vestibuli and the scala tympani. Both those compartments, as I mentioned, contain perilymph. The scala vestibuli starts at the oval window, and the scala tympani ends at the round window. They contain perilymph.

01:45 And actually those two chambers come together and the perilymph passes between one on the other at the very apex of the cupula at a place called the helicotrema. And you can see on the left-hand diagram the very apex part of the cochlea.

02:07 So again, the organ of Corti is embedded in endolymph. Above it, you can see a very small membrane. That's the vestibular membrane. And the organ of Corti actually sits on a basilar membrane, separating the endolymph from the perilymph of the scala tympani.