Internal ear
a central cavity (the vestibule), semicircular canals (which open into the vestibule) and the cochlea (a snail-shaped spiral tube). The membranous labyrinth also has a vestibule which consists of two sacs (called the utriculus and sacculus) connected by a narrow tube. The utriculus, the larger of the two sacs, is the principal organ of the vestibular system (which informs us about the position and movement of the head). The smaller of the two sacs, the sacculus (literally, the little sac) is connected with a membranous tube in the cochlea containing the organ of Corti. It is in the organ of Corti that are situated the hair cells, the special sensory receptors for hearing. The internal ear is also called the inner ear.
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