GENERAL HISTOLOGY

Detailed explanation-1: -Echinoderms are exclusively marine organisms with spiny bodies. They have an endoskeleton rich in calcium, basically made of calcareous ossicles .

Detailed explanation-2: -Echinoderms have a spiny endoskeleton. They have radial symmetry as adults but bilateral symmetry as larvae. Echinoderms have a unique water vascular system with tube feet.

Detailed explanation-3: -While many echinoderms do begin life as a bilateral larva, later they become radial with five-part symmetry and no central brain. The bodies of echinoderms are made of hard calcium-based plates that are often spiny and always covered by a thin skin. The echinoderm skeleton is thus on the inside-called an endoskeleton.

Detailed explanation-4: -Echinoderms have an exoskeleton made up of spicules. These spicules are spiny structures that are made up of Calcium carbonate minerals. They are very hard and provide a tough and protective skeleton for the body.

Detailed explanation-5: -Echinoderms do not have an exoskeleton. The skeleton of echinoderms is composed of calcium carbonate plates that are enclosed or covered by a thin layer of skin (epidermis) and supported by the mesodermal tissue and therefore, this is an endoskeleton.