Anterior semicircular canal

Nerves · Latin: Canalis semicircularis anterior

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The anterior (superior) semicircular canal is one of three fluid-filled bony loops, each about 6 mm across and at right angles to the others, that sense turning of the head. Each canal has a swelling at one end, the ampulla, holding a crest of hair cells capped by a jelly flap (the cupula). When the head turns in the canal's plane the fluid lags behind, bends the cupula and changes the firing of the nerve. The anterior canal stands upright at about 45 degrees to the midline and mostly senses nodding and tilting of the head. Its inner end joins the posterior canal's upper end in the common crus. This model is a simplified shape built from textbook measurements.