Semicircular ducts

  • The semicircular ducts are three membranous canals that resemble two thirds of a circular arch, each occupying its own bony semicircular canal oriented perpendicular to the others.

    The anterior semicircular duct (latin: ductus semicircularis anterior) is a membranous tube  located in the bony labyrinth of the inner ear forming about two thirds of a circle. It is oriented in the vertical plane and somewhat perpendicular to the petrous part of the temporal bone, situated medially and laterally over the roof of the utriculus. The anterior semicircular duct detects vertical head movements when the head is moved up and down.

    The lateral semicircular duct (latin: ductus semicircularis lateralis) is a membranous tube forming about two thirds of a circle and is oriented in the horizontal plane. It has two openings in the lateral wall of the utriculus. The lateral semicircular duct detects angular acceleration of the head.

    The posterior semicircular duct (latin: ductus semicircularis posterior) is a membranous tube forming about two thirds and oriented in the vertical plane and in a plane parallel to the longitudinal axis of the petrous part of the temporal bone, directed downwards and laterally behind the utriculus. The posterior semicircular duct detects vertical head movements when the head is moved up and down.