Posterior semicircular canal

Nerves · Latin: Canalis semicircularis posterior

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The posterior semicircular canal is the upright canal that lies along the back surface of the petrous bone, at right angles to the anterior canal of the same ear. It senses turning of the head in its plane, mostly tipping the head towards the shoulder and nodding. Its ampulla is at its lower end; its upper end joins the anterior canal in the common crus. Loose crystals from the utricle that drift into it are the usual cause of benign paroxysmal positional vertigo: short spells of spinning when lying down or rolling over in bed. This model is a simplified shape built from textbook measurements.