Final answer:
The semicircular canals are found in both the auditory and vestibular systems of the inner ear, playing a key role in balance and spatial orientation by detecting head movements and sending signals to the brain.
Step-by-step explanation:
The structure that is found in both the auditory system and the vestibular system is the semicircular canals. These canals are part of the vestibular apparatus that helps in maintaining balance and orientation in space. In the auditory system, while the semicircular canals themselves don't directly facilitate hearing, they are contained within the same bony labyrinth as the cochlea, which is the primary organ for hearing. The vestibular system, including the semicircular canals, is responsible for our sense of balance and spatial orientation, aiding in activities such as standing, walking, and any movement that requires us to maintain our posture and equilibrium.
As part of the inner ear structure, the semicircular canals contain fluid and hair cells. When we turn our head or move it in any direction, the fluid in the canals moves. This movement bends the hair cells within the canals, and they send signals to the brain via the vestibular nerve, informing it of the direction and speed of the movement. The brain integrates this information to help us balance and move smoothly.