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.
1. Expanded ampullary sac and
2. 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.