Posterior semicircular canal

The posterior semicircular canal, vertical like the superior, is directed backward, nearly parallel to the posterior surface of the petrous bone. It is part of the bony labyrinth and is used by the vestibular system to detect rotations of the head in the sagittal plane.

It is the longest of the three canals, measuring from 18 to 22 mm.

Its lower or ampullated end opens into the lower and back part of the vestibule, its upper into the crus commune already mentioned.