Editing Cochlea (section)

=== Microanatomy ===
The walls of the hollow cochlea are made of bone, with a thin, delicate lining of [[Epithelium|epithelial tissue]]. This coiled tube is divided through most of its length by an inner membranous partition. Two fluid-filled outer spaces (ducts or ''scalae'') are formed by this dividing membrane. At the top of the snailshell-like coiling tubes, there is a reversal of the direction of the fluid, thus changing the vestibular duct to the tympanic duct. This area is called the helicotrema. This continuation at the helicotrema allows fluid being pushed into the vestibular duct by the oval window to move back out via movement in the tympanic duct and deflection of the round window; since the fluid is nearly incompressible and the bony walls are rigid, it is essential for the conserved fluid volume to exit somewhere.

The lengthwise partition that divides most of the cochlea is itself a fluid-filled tube, the third 'duct'. This central column is called the cochlear duct. Its fluid, endolymph, also contains electrolytes and proteins, but is chemically quite different from perilymph. Whereas the perilymph is rich in sodium ions, the endolymph is rich in potassium ions, which produces an [[ion]]ic, electrical potential.

The hair cells are arranged in four rows in the organ of Corti along the entire length of the cochlear coil. Three rows consist of outer hair cells (OHCs) and one row consists of inner hair cells (IHCs). The inner hair cells provide the main neural output of the cochlea. The outer hair cells, instead, mainly 'receive' neural input from the brain, which influences their [[motility]] as part of the cochlea's mechanical "pre-amplifier". The input to the OHC is from the [[olivary body]] via the medial olivocochlear bundle.

The cochlear duct is almost as complex on its own as the ear itself.  The cochlear duct is bounded on three sides by the [[basilar membrane]], the ''[[stria vascularis]]'', and Reissner's membrane.  The ''stria vascularis'' is a rich bed of capillaries and secretory cells; Reissner's membrane is a thin membrane that separates endolymph from perilymph; and the basilar membrane is a mechanically somewhat stiff membrane, supporting the receptor organ for hearing, the organ of Corti, and determines the mechanical wave propagation properties of the cochlear system.