Enchondral Ossification
The long bones are created by the ossification of cartilaginous skeleton, which functions as the precursor of the definitive skeleton. It is of mesodermal origin and the ossification occurs by the replacement of cartilage by bone. In enchondral ossification, the mesoderm first develops into cartilage and then into bone (in the neurocranium, mesenchyme from the neural crest is converted directly into bone).