The vestibular apparatus is important for keeping one`s balance, and for spatial orientation. It consists of three differently arranged semicircular ducts with each one receptor organ (lat. crista ampullaris), as well as utriculus and sacculus, whose receptor organ is the macula statica (lat.). The receptor organs consist of supporting cells, between which secondary sensory cells are embedded. These have hair on their surface, each one kinocilium (sensory hair) and several stereocilia (microvilli without proper motion), that extend into a gelatinous layer. When this layer is deflected due to a movement, the sensory hairs are bent: If the sensory hair bends towards the stereocilia, the nerve fiber is inhibited, if it bends away from the microvilli, it`s activated. There are crystals (gr. statoliths) laying on the gelatinous layer of the macula statica. The cristae ampullares primarily register angular, the maculae staticae linear acceleration.
