The part of the vertebrate ear which contains
the organs of hearing and balance (see vestibular
sense). The inner ear is surrounded by the temporal
bone of the skull and is connected to
the brain by the auditory
nerve. It consists of of two connected chambers with sensory walls.
From one, the utricle, arise the semicirculuar
canals, which are concerned with balance. From the other, the sacculus,
arises the cochlea. The whole inner ear
is filled with a fluid (endolymph) and is separated from the surrounding
skull wall by another fluid (perilymph).