The cochlea propagates these mechanical signals as waves in the fluid and membranes and then converts them to nerve impulses which are transmitted to the brain.

The type of motion or attitude detected by a hair cell depends on its associated mechanical structures, such as the curved tube of a semicircular canal or the calcium carbonate crystals (otolith) of the saccule and utricle.

They contain the sensory hair cells and otoliths of the macula of utricle and of the saccule, respectively, which respond to linear acceleration and the force of gravity.

The utricular division of the auditory vesicle also responds to angular acceleration, as well as the endolymphatic sac and duct that connect the saccule and utricle.

Beginning in the fifth week of development, the auditory vesicle also gives rise to the cochlear duct, which contains the spiral organ of Corti and the endolymph that accumulates in the membranous labyrinth.

[6] The vestibular wall will separate the cochlear duct from the perilymphatic scala vestibuli, a cavity inside the cochlea.

The lateral wall of the cochlear duct is formed by the spiral ligament and the stria vascularis, which produces the endolymph.

The hair cells develop from the lateral and medial ridges of the cochlear duct, which together with the tectorial membrane make up the organ of Corti.

Both types of pillar cell have thousands of cross linked microtubules and actin filaments in parallel orientation.

Hardesty's membrane is the layer of the tectoria closest to the reticular lamina and overlying the outer hair cell region.

Neurons within the ear respond to simple tones, and the brain serves to process other increasingly complex sounds.

Georg von Békésy (1899–1972) employed the use of a microscope in order to examine the basilar membrane located within the inner-ear of cadavers.

He found that movement of the basilar membrane resembles that of a traveling wave; the shape of which varies based on the frequency of the pitch.

It is a fairly rare disorder while at the same time, a lack of proper diagnostic testing has meant that its precise incidence cannot be determined.

The cochlea of birds is also similar to that of crocodiles, consisting of a short, slightly curved bony tube within which lies the basilar membrane with its sensory structures.

From here, sound waves are conducted through a short perilymphatic duct to a second opening, the round window, which equalizes pressure, allowing the incompressible fluid to move freely.

The lagena is separated from the perilymphatic duct by a basilar membrane, and contains the sensory hair cells that finally translate the vibrations in the fluid into nerve signals.

[12] In most reptiles the perilymphatic duct and lagena are relatively short, and the sensory cells are confined to a small basilar papilla lying between them.

As a result of this increase in length, the basilar membrane and papilla are both extended, with the latter developing into the organ of Corti, while the lagena is now called the cochlear duct.

[12] In therian mammals, the lagena is extended still further, becoming a coiled structure (cochlea) in order to accommodate its length within the head.

[12] Although many fish are capable of hearing, the lagena is, at best, a short diverticulum of the saccule, and appears to have no role in sensation of sound.

The central part of the system consists of two chambers, the saccule and utricle, each of which includes one or two small clusters of sensory hair cells.

All jawed vertebrates also possess three semicircular canals arising from the utricle, each with an ampulla containing sensory cells at one end.

In amphibians the sacs from either side may fuse into a single structure, which often extends down the length of the body, parallel with the spinal canal.

The inner ear in these species consists of a single vestibular chamber, although in lampreys, this is associated with a series of sacs lined by cilia.