Endoskeleton means internal skeleton.

All vertebrates and a few invertebrates, the echinoderms, have an endoskeleton.

As opposed to an exoskeleton, an endoskeleton grows as the organism grows. The endoskeleton is usually made up of bones. Endoskeletons of vertebrates are made up of two parts.

• The axial skeleton, which includes the backbone, skull and ribs.
• The appendicular skeleton, which includes the bones of the appendages such as arms, legs, hips and shoulders.