Semicircular canals are three tiny fluid-filled tubes inside each side of the ear that help in maintaining balance and sense of direction. The canals contain a fluid which sloshes around as the head moves, making the tiny hairs that line the canal move. The movements of these hairs send messages to the brain that is perceived as movement and balance.
When you spin around for a few seconds and stop suddenly, the fluid in these canals continues to move sending information of movement to the brain. This is the reason you feel dizzy after spinning around or going round and round in the rides at the amusement park.
The three semicircular canals in each ear are situated at right angles to each other. Movement of the head in different planes stimulates fluid in the particular canal. When the movement of the head in not exactly in the direction of one of the canals, the fluid in more than one canal is stimulated.
The three semicircular canals are:
The ends of the three semicircular canals joint to form a common stem.
Let us see how we feel the motion:
Damage to the semicircular canals may cause serious problems in sense of balance. Usually, hearing is also affected as the semicircular canals are located in the vestibular portion of the ear.
Superior canal dehiscence syndrome (SCDS) is a congenital condition in which the canal fails to close or thicken in the normal way. This condition leads to the following symptoms:
Diagnosis of the condition is done using tests like vestibular symptoms and signs, CT imaging tests and testing of the reaction of muscles behind the ear by stimulating them.
Semicircular canals, along with vision and somatosensory system (involving the skin, muscles and joints) play an important role in maintaining balance, which is an important aspect of each and every movement.