Anterior semicircular canal

Canalis semicircularis anterior

Sensory (eye & ear)OrgansHeadLeft and right

View left in 3D View right in 3D

What it is

The anterior (superior) semicircular canal arches upward in a vertical plane set at about 45 degrees to the midline, at right angles to the long axis of the petrous bone. Its dilated ampulla lies at the anterolateral end; its other limb joins the posterior canal in a common crus.

Function

Senses rotation of the head in its own plane, such as nodding forward and down.

Size

Radius of curvature about 3.2-4 mm; bony lumen about 1 mm, membranous duct 0.3 mm; ampulla about 2 mm.

Clinical note

Its summit raises the arcuate eminence on the floor of the middle cranial fossa; a thinned roof (superior canal dehiscence) lets patients hear their own eye movements.