Of what substance is the developing human embryonic skeleton initially composed; what new substance increasingly replaces the initial skeletal substance? What characteristics of cartilage make it suitable for forming body parts that require both flexibility and strength? What parts of the body does cartilage form?
In the human embryo, the early skeleton is formed of cartilage which is gradually replaced by bone as development progresses. Cartilage is a specialized form of dense connective tissue with a rather rubbery intercellular matrix, and, like all types of dense connective tissue, cartilage has a relatively small quantity of connective tissue cells. These characteristics make cartilage flexible and somewhat elastic yet very strong. Thus, cartilage is found in those parts of the body where both flexibility and firmness are required: cartilage forms parts of the nose and ears as well as the larynx, trachea, end of ribs, inter vertebral discs, and surfaces of skeletal joints.
