GENERAL HISTOLOGY

Detailed explanation-1: -The endoskeleton of echinoderms is composed of plates, known as ossicles, that are formed from networks of calcium carbonate crystals called the stereom.

Detailed explanation-2: -Echinoderm skeletons are made up of interlocking calcium carbonate plates and spines. This skeleton is enclosed by the epidermis and is thus an endoskeleton. In some, such as sea urchins, the plates fit together tightly.

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: -Ossicles are small calcareous elements embedded in the dermis of the body wall of echinoderms. They form part of the endoskeleton and provide rigidity and protection. They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids.

Detailed explanation-5: -Echinoderms possess a unique internal skeleton (or endoskeleton) composed of thousands to millions of calcium carbonate components known as ossicles.