GENERAL HISTOLOGY

Detailed explanation-1: -The echinoderms have an open circulatory system, meaning that fluid moves freely in the body cavity. But echinoderms have no heart. This may be due to their simple radial symmetry-a heart is not needed to pump the freely moving fluid.

Detailed explanation-2: -Echinoderms also lack a centralized nervous system. They have an open circulatory system and lack a heart. On the other hand, echinoderms have a well-developed coelom and a complete digestive system. Echinoderms use pheromones to communicate with each other.

Detailed explanation-3: -Echinoderms do not have a true circulatory system like the ones found in humans or other mammals. Instead, they have a system of fluid-filled canals throughout their bodies that perform many of the functions that our circulatory systems do.

Detailed explanation-4: -The phyla in which the circulatory system is open and the body cavity is filled with blood are present in Mollusca and Arthropoda. Open circulatory systems work by pumping blood into a hemocoel. The species in the phylum Arthropoda have an open circulatory system.