Endoskeleton

As endoskeleton (also called internal skeleton ) is known in biology, a mechanical support structure ( skeleton), which is not part of the outer shell of the body. It is one of the most striking common features of vertebrates ( Vertebrata ).

An endoskeleton is composed of rigid elements ( so-called hard portions ) which can be moved over each other muscles. In humans, as in most vertebrate groups, these elements consist of calcium phosphate and collagen and are referred to as bone. Other important building blocks of endoskeletons of vertebrates are the cartilage that do not contain mineral substance.

The skeleton of the echinoderms ( Echinodermata ) whose hard parts are made of calcium carbonate, is not like the lime shells of snails and mussels, a part of the body surface, but underneath lies a thin epidermis and is therefore also an endoskeleton.