GENERAL HISTOLOGY

Detailed explanation-1: -The sea star’s skeleton, like the sea urchin’s, is an endoskeleton consisting of small plates of calcium carbonate embedded in the epidermis. These plates, called ossicles, are much smaller than those of sea urchins.

Detailed explanation-2: -Plates are tabular ossicles that fit neatly together in a tessellated manner. They form the main skeletal covering for sea urchins and sea stars. Spines are ossicles that project from the body wall and articulate with other ossicles through ball and socket joints mounted on tubercles.

Detailed explanation-3: -Echinoderms possess a unique internal skeleton (or endoskeleton) composed of thousands to millions of calcium carbonate components known as ossicles. Similar to a complicated 3-D puzzle, these pieces are infused with tissue and covered by an epidermis, or skin like covering.

Detailed explanation-4: -Echinoderms have an internal skeleton made of bony plates (ossicles) of calcium carbonate. They deposit this material after extracting dissolved calcium and carbonate (bicarbonate) ions from sea water. In some species, such as the sea urchin, plates of the skeleton are locked together to form a rigid structure.