Vestibule of inner ear

Nerves · Latin: Vestibulum

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The vestibule is the central chamber of the bony labyrinth, about 4 to 5 mm across, between the cochlea in front and the semicircular canals behind. The footplate of the stapes sits in the oval window in its outer wall. It holds the utricle and the saccule, two sacs each with a patch of hair cells under a jelly layer weighted with tiny crystals of calcium carbonate (otoconia). When the head tilts or moves in a straight line the crystals lag behind and bend the hairs, which tells the brain which way is down and how the head is speeding up or slowing down. The signals travel in the vestibular nerve. This model is a simplified shape built from textbook measurements.