Diagram of the key measurements made from the organ of Corti to illustrate the differences between dimensions at the base and apex of the cochlea.

The profiles illustrated in this figure were taken from histological sections cut near to the apex and close to the base of a guinea pig cochlea. The profile from the apex is labeled to indicate the basilar membrane (bm), reticular lamina (rl), inner and outer pillar cells (ipc, opc), a single Deiters' cell (Dc) and a single outer hair cell (ohc). The lower profile from the base illustrates the angle between the upper ends of ipc and opc (α), and inside the arch of Corti between the ipc and bm (β) and between the opc and the bm (χ). The distance w defines the separation between the bottom ends of the ipc and opc. Note that the greatest measured changes in cell length were in the ohc and opc with the length of the Dc remaining almost constant. Whilst w decreased towards the base the associated changes in cell length meant that α remained almost constant.