The semicircular canals are part of the inner ear. They are lined with cilia and filled with a fluid known as endolympth. Every time the head moves, the endolymph moves the cilia. This works as a type of motion sensor, as the movements of the cilia are communicated to the brain. As a result, the brain knows how to keep the body balanced in all postures. The semicircular canals contain three main parts: the horizontal, posterior, and superior canals. Each of these canals provides a separate sense of directional balance. The superior canal detects head rotations on the anterior-posterior axis. The posterior canal detects rotations on the saggital plane. The horizontal canal senses movement on a vertical basis, as the head rotates up-and-down on the neck. Damage or injury to the semicircular canals may be twofold. If any of the three separate parts do not work, a person can lose their sense of balance. A diminished ability to hear may also result from any damage.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Semicircular canals