It’s easy enough to assume that if a part of the human body is inside the ear, then it must help a person to hear in some way. But that’s not necessarily true of the semicircular canals, which are part of the inner ear. Instead, they help a person maintain a sense of balance.
The semicircular canals inside the inner ear are lined with cilia. These are very tiny hairs, and they’re filled with a liquid substance that’s called endolymph.
Whenever you move your head, the liquid endolymph moves much like the water in a cup moves when you move the cup. The endolymph in turn moves the cilia. The cilia movements are then communicated to your brain, which makes the cilia function as some sort of motion sensor. The brain interprets the information from the cilia and instinctively sends messages to the rest of the body so that your body can keep its balance, regardless of your posture.
It’s fair to describe the semicircular canals as a grouping of 3 tiny tubes or canals filled with fluid. These are the anterior, posterior, and horizontal canals. Every one of these canals gives a distinct sense of directional balance, and each canal on one ear works with its counterpart in the other ear. The anterior canal senses head movements that go forward and back, such as if you’re nodding your head. The posterior canal senses head tilts, such as if you tip your head toward your right shoulder. The horizontal canal senses the horizontal movement of your head, such when you swivel your head from side to side.
You may remember a children’s game in which you spin in place for an extended period of time and then right after you’re supposed to walk in a straight line. Most children (and adults for that matter) find it difficult to maintain their balance as they try to walk in a straight line. The reason for this is that after you’re done spinning in place, the liquid inside the canals are still moving. The cilia still detect the movement of the liquid, like how your coffee is still moving even after you’re done stirring it with a spoon.
The microscopic hairs continue to tell your brain that you’re still spinning even when you’ve already stopped. These conflicting reports result in your rather poor sense of balance. This is also the reason why you may feel dizzy during car trips and amusement park rides. It’s not an inherent weakness on your part. It’s just that your ears, or at least your semicircular canals, are working as they’re sup
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