On the upper and lower surfaces of the head a number of tin- branched structures are present. They are called ampullae of lorenzini. Each ampulla contains two parts. Expanded ampullary sac and A long narrow ampullary canal. The ampullary sac contains 8 to 9 chambers. They are separated by septal walls. They are arranged around a central axis. These chambers contain sensory papillae. These sensory papillae are connected with nerve fibers.The ampullary canal is long and narrow. It is filled with mucus. It opens out through a pore. These sense organs will work as thermo receptors. They detect the temperature changes of the water. They also detect the changes in the pressure.