Circulation

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Echinoderms have a simply, but unique feature for circulation. They have a system of internal tubes filled with water that are part of the water vascular system. The water vascular system carries out many essential body functions needed for echinoderms like: respiration, circulation, and movement. This structure of water filled canals connecting numerous tube feet.

Other than the water vascular system, echinoderms have few adaptations to carry out respiration or circulation. Most species of echinoderms have thin-walled tissue that make up the tube feet. The tube feet provide the main surface for respiration. In other species skin gills, small outgrowths, also function in gas exchange.

Circulation of needed materials (such as oxygen and food) and wastes takes place throughout the water vascular system.

Movement & Support

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  An echinoderms mobility is determined in part by the structure of the endoskeleton it has. Most echinoderms moce using their tube feet and thin layers of muscle fibers attached to their endoskeleton. 
    The echinoderms called the sand dollar and sea urchins have movable spines attached to the endoskeleton, while sea stars and brittle stars have flexible joints that enable them to use their arms for movement. The sea cumbers crawl along the ocean floor by the combined action of tube feet and the muscles of the body wall. The body walls, which are soft and muscular, in sea cumbers contain reduced plates of endoskeleton.