GENERAL HISTOLOGY

Detailed explanation-1: -Tube feet not only help the urchin move, they also are used to grasp food, and they are part of the respiratory or breathing system. Sea urchin extending beyond the spines.

Detailed explanation-2: -Sea stars have a water vascular system and tube feet much like those of the sea urchins. Ambulacral grooves (from the Latin root ambul meaning walk) are narrow channels in the oral surface of a sea star filled with tube feet. The tube feet are used mainly for grabbing and locomotion.

Detailed explanation-3: -It is these suction-bottomed tubes that the sea star uses to move about. It draws in water and channels it to canals that run throughout its body, usually ending in the tube feet. By changing the pressure of water in its body, the sea star can move the tubed feet, and thus move forward.

Detailed explanation-4: -Mucus on the tube feet can trap phytoplankton, bacteria, and even medusae from the water or particles from sediment that are moved by the tube feet to the mouth; some ophiuroids capture small crustaceans or worms by looping the organisms with their rays.