Otolithic membrane

The otolithic membrane is a gelatinous membrane located in the vestibular apparatus of the inner ear, and plays an essential role in the brain's interpretation of equilibrium. Both the saccular macula and utricular macula are covered by an otolithic membrane, thus providing the common name of "the otoliths" to the untricle and saccule.

The membrane is composed of crystalline particles of calcium carbonate called otoliths. When the head is moved the otoliths shift, causing cilia in the nearby saccule and utricle to distort. This produces nerve signals which are sent to the brain, which then uses them to establish its sense of balance.

The embedded crystals are very and dense and make the density of the otolithic membrane higher than that of the endolymph surrounding it. When the head accelerates along a line or tilts to change its orientation to gravity, the otolithic membrane shifts relative to the bone supporting the maculae. This shift bends the hair cells whose processes are embedded in the otolithic membrane.