GENERAL HISTOLOGY

Detailed explanation-1: -The water vascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. The system is composed of canals connecting numerous tube feet.

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: -Excretion in echinoderms is by simple diffusion of metabolic wastes (ammonia) across thin permeable regions of the body wall. A variety of gas exchange structures, including the tube feet, is found in various echinoderms.

Detailed explanation-4: -Echinoderms lack specialized excretory (waste disposal) organs and so nitrogenous waste, chiefly in the form of ammonia, diffuses out through the respiratory surfaces.

Detailed explanation-5: -Echinoderms do not have primary excretion organs, but instead expel their nitrogenous waste through their respiratory system in the form of ammonia. > However, the anus is present in most echinoderms and is often used to jettison waste.