GENERAL HISTOLOGY

Detailed explanation-1: -Echinoderms have a unique water vascular system. This network of fluid-filled tubes helps them to breathe, eat, and move. Therefore, they can function without gill slits. Echinoderms also have a very simple digestive system, circulatory system, and nervous system.

Detailed explanation-2: -How Do Echinoderms Breathe? Echinoderms have a simple respiratory system. Depending on the species, they breathe by diffusion through simple gills or projections on their bodies, such as tube feet.

Detailed explanation-3: -The bodies of echinoderms are made of tiny, hard calcium-based plates. The plates are often spiny and always covered by a thin skin. Because the echinoderm skeleton is on the inside, it is called an endoskeleton. Echinoderms seem little more than a skeleton of tiny plates and water.

Detailed explanation-4: -The spines serve a protective function and are also used for locomotion. Pedicellariae are compound ossicles that articulate with other ossicles and protrude from the aboral (upper) surface of some sea stars (and also the test of sea urchins).