Editing Inner ear (section)

===Vestibular system===
By comparison with the [[cochlea]]r system, the [[vestibular system]] varies relatively little between the various groups of [[gnathostome|jawed vertebrates]]. 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 [[osseous ampullae|ampulla]] containing sensory cells at one end.<ref name=VB/>

An [[endolymphatic duct]] runs from the saccule up through the head and ending close to the brain. In [[cartilaginous fish]], this duct actually opens onto the top of the head, and in some [[teleost]]s, it is simply blind-ending. In all other species, however, it ends in an [[endolymphatic sac]]. In many reptiles, fish, and amphibians this sac may reach considerable size. 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]].<ref name=VB/>

The primitive [[lamprey]]s and [[hagfish]], however, have a simpler system. 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]]. Lampreys have only two semicircular canals, with the horizontal canal being absent, while hagfish have only a single, vertical, canal.<ref name=VB/>