Semicircular Canals
Anatomy
The semicircular canals are three tiny, fluid-filled tubes in your inner ear that help you keep your balance. When your head moves around, the liquid inside these canals sends signals to the brain to help it sense body motion and maintain balance.
The three canals are arranged roughly at right angles to each other, and are called the horizontal (or lateral), the anterior (or superior) and the posterior (or inferior) semicircular canals. Each of these canals is filled with a fluid called endolymph and contains a motion sensor with tiny hairs whose ends are embedded in a jelly-like cupula. When you move your head, the fluid in the canals moves and causes the cupula to flex, which in turn causes the hairs to bend. The bending of these hairs generates nerve impulses that are sent to the brain to interpret.
Function
The semicircular canals are part of the vestibular system, which contributes to our sense of balance and spatial orientation. The canals are sensitive to rotations of the head, so they play a crucial role in our perception of movement and maintaining balance.
Each of the three semicircular canals has a different orientation and each is responsible for a different type of head movement: up-and-down, side-to-side, and tilting from one side to the other. All three canals work together to send the brain complete information about the body's motion and orientation.
Clinical Significance
Problems with the semicircular canals can lead to issues with balance, including dizziness and vertigo. One common condition is benign paroxysmal positional vertigo (BPPV), which causes short episodes of mild to intense dizziness. BPPV occurs when tiny calcium particles clump up in the inner ear, causing brief episodes of mild to intense dizziness. BPPV can occur for no known reason and is often associated with age.
Meniere's disease is another condition that affects the inner ear and causes episodes of vertigo. This condition is thought to be caused by changes in the fluid in tubes of the inner ear. Other symptoms of Meniere's disease include ringing in the ear (tinnitus) and hearing loss.