The semicircular canals are three bony canals within the internal ear situated behind the vestibule and arranged in three mutually perpendicular planes. The semicircular canals of the bony labyrinth contain perilymphatic fluid and the membranous semicircular ducts.
The anterior semicircular canal (latin: canalis semicircularis anterior) is oriented vertically and somewhat perpendicular to the axis of the petrous part of the temporal bone. It shares a common crus with the posterior semicircular canal.
The posterior semicircular canal (latin: canalis semicircularis posterior) is the posterior and most inferior semicircular canal that is oriented somewhat vertically and parallel to the longitudinal axis of the petrous part of the temporal bone. It shares a common crus with the anterior semicircular canal.
The lateral semicircular canal (latin: canalis semicircularis lateralis) is oriented horizontally and sometimes creates a bulge in the medial wall of the tympanic cavity.
Each semicircular canal of the bony labyrinth is filled with perilymph and encloses the corresponding semicircular duct of the membranous labyrinth, which is filled with endolymph.