ABSTRACT
The lateral line organs and the organs of the inner ear, the semicircular canals and otolith organs, are mechanical displacement detectors that share a common hair cell receptor structure. Receptor cells and adjacent support cells make up the sensory epithelia of the mechanosensory organs; the neuromasts, cristae and maculae of the mechanosensory lateral line, semicircular canals and otolith organs, respectively. The mechanosensory receptor cell has an arrangement of displacement-sensitive ‘hairs’ that project from the apical surface to form an asymmetric assemblage of stereocilia that progressively increase in length along an axis approaching a longer, single, more rigid kinocilium. The stereocilia-kinocilium complex of mechanosensory lateral line and semicircular canal organs project into an acellular gelatinous mass, the cupula, which is secreted by support cells within the sensory epithelium.
