Final answer:
The receptor hair cells in each semicircular canal are located on top of a saddle-shaped ridge in the ampulla, which is a swelling at the base of the canal.
Step-by-step explanation:
The semicircular canals are part of the vestibular system, which is responsible for detecting changes in head position and rotational movement. Each semicircular canal has a swelling called the ampulla, where receptor hair cells are located.
These hair cells respond to rotational movement and are situated on top of a saddle-shaped ridge in the ampulla. The cupula, a membrane, is connected to the top of the ampulla and contains stereocilia that are bent by the movement of fluid in the canals, sending signals to the brain.