Final answer:
The semicircular canals are cartilage-containing structures in the inner ear that are responsible for detecting changes in head position and rotational movements. They are filled with fluid and hair cells and play a crucial role in maintaining balance and coordination.
Step-by-step explanation:
The semicircular canals are part of the inner ear and are responsible for detecting changes in head position and rotational movements. They are cartilage-containing structures that are filled with fluid and hair cells. When the head moves, the fluid in the semicircular canals also moves, stimulating the hair cells and sending signals to the brain to help maintain balance and coordination.