Cochlear Anatomy

Cross-section of the cochlea

Image produced in collaboration with Dr Robert Kimura, Harvard University.
This slide shows a mid-modiolar section through the cochlea. The cochlea consists of a single bony tube which spirals around a middle "core" containing the auditory nerve. Similar to a snail, the spaces are larger in the basal turn (lower part of the figure) than they are in the apex (upper part of the figure). In each turn, the bony tube is divided into three separate compartments by the membranous tissues.

Cross-section through one cochlear turn

This section shows how each turn of the cochlea is divided into three chambers, called scalae. Scala tympani and scala vestibuli contain perilymph. Scala media contains the endolymph which is bounded on three sides by stria vascularis, Reissner's membrane and the organ of Corti. The organ of Corti contains the sensory "hair cells" which tranduce mechanical stimuli (sound) into electrical signals.

Schematic of one cochlear turn

This schematic shows the fluid spaces of one turn of the cochlea.
The perilymph is shown orange and the endolymph is shown blue. Although the chemical composition of perilymph in scala vestibuli and scala tympani is slightly different, these compartments are not independent of each other. There is considerable "cross-communication" across the spongy spiral ligament in all turns of the cochlea, so that substances present in scala tympani will rapidly diffuse into scala vestibuli (and vice versa).

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Page generated by: Alec N. Salt, Ph.D.,
Cochlear Fluids Research Laboratory,
Washington University, St. Louis