Final answer:
The vestibular system of the inner ear, consisting of the utricle, saccule, and three semicircular canals, is responsible for maintaining body equilibrium by sensing head position and movement.
Step-by-step explanation:
The structure of the inner ear that helps to maintain body equilibrium is the vestibular system, which includes the utricle, saccule, and three semicircular canals. These structures work together to sense head position and movement, allowing us to maintain balance. The utricle and saccule are sensitive to linear movements, like gravity, due to their hair cells topped with a gelatinous layer containing calcium carbonate crystals. When the head tilts, these crystals move, causing the gelatin to shift and the stereocilia to bend. This bending stimulates neurons that signal the brain about head orientation. On the other hand, the semicircular canals are responsive to angular movements, like turning the head. They too contain fluid and hair cells that monitor the fluid's movement and send signals to the vestibulocochlear nerve, which communicates with the brain to help maintain balance.