"A series of three illustrations are shown. The top illustration shows a cochlea, which is shaped like a snail shell with two parallel chambers, the upper chamber and the lower chamber, coiling from the outside in. These chambers are separated by a flexible membrane basilar membrane. The oval window covers the inner of these parallel chambers. Sound waves enter here, and travel to the middle, or apex, of the coil. The membrane separating the two chambers gets thinner from the outside in, such that is vibrates at different sound frequencies, about 20,000 hertz on the outside and about 200 hertz on the inside. Sound then travels back out through the lower chamber, and exits through the round window. The middle illustration shows a closer view of a cross-sectional image of the cochlea. A roughly circular shape has a roughly circular bone exterior, with the middle portion of the circle divided into four major areas. Two of these are spaces labeled ""upper canal"" and ""lower canal."" In the middle is the organ of Corti, and extending from the middle out through the outer bone area is the cochlear nerve, which extends from the middle as a thin tube and then bulges into a larger oval shape as it extends through the bone. The bottom illustration is an enlarged image of the organ of Corti. In the view shown, the top section is a flattish pink area called the tectorial membrane. Extending beneath that membrane are three areas with hair-like connectors (stereocilia) that run from the membrane to the outer hair cells. The outer hair cells are shaped like rectangles with rounded corners. From the end of each protrudes a narrow tube: the cochlear nerve. These narrow tubes join to an inner hair cell, which looks similar to the outer hair cells but with its rectangular shape remaining a consistent width instead of narrowing into a nerve. At the bottom of the image, opposite the top tectorial membrane, is a basilar membrane."
{}