We propose a set of models for the mechanical and hydrodynamical processes in the organ of Corti (OoC). In this model the motion of the basilar membrane is provided as input, and we concentrate on the other components of the OoC. The model consists of a set of equations, all based on Newton's laws, describing the motions and mutual interactions of the outer hair cells, the outer hair bundles, Deiters cells, the reticular lamina, Hensen cells, and the inner hair bundle. In addition, the model includes the equations describing the endolymph fluid motion in the subtectorial channel. A key ingredient in the model is the nonlinear constitutive laws governing the vibrations of the outer hair bundles and outer hair cells. The inner hair bundle oscillates via interaction with the endolymph flow. It is shown that under a minimal set of assumptions, and using basic mechanical principles, the components of the OoC listed above can act as a second filter, along with the basilar membrane filter, that enhances frequency selectivity, amplitude compression and signal to noise ratio