A skeleton that is internal is known as an endoskeleton. It is a bony and cartilaginous structure that comprises the axial and appendicular skeleton. Endoskeletons are found in vertebrates, including humans.
The internal skeletons of vertebrates may also be called bony skeletons. These skeletons are composed of calcified bone tissue. It is created through the process of ossification using bone precursor cells known as osteoblasts, which replace softer cartilage tissue that was previously formed. The skeleton in its entirety is made up of bone, cartilage or a combination of the two. The function of skeletons, including endoskeletons, is to provide support for the body and its internal soft tissue.