Final answer:
Most bones originate from cartilage, transitioning to bone through endochondral ossification, a process that begins during fetal development and continues as children grow.
Step-by-step explanation:
Most bones in the human body develop from cartilage through a process known as endochondral ossification before a baby is born. After birth, bones continue to grow and ossify through the existence of cartilage at growth plates.
In fetal development, the human skeleton starts as cartilage, which is a flexible connective tissue. This cartilage is gradually replaced by hard bone in a process termed ossification. Ossification starts at a primary ossification center in the middle of bones and later at secondary ossification centers at the ends of bones.
The axial skeleton begins to form during early embryonic development and continues to develop after birth. While most of the cartilage is converted to bone by the time of birth, certain areas known as growth plates allow for the lengthening of bones during childhood. Endochondral ossification is essential for the formation of the long bones of the arms and legs, as well as other skeletal structures.