9.7 Development of joints  (Page 6/7)

Intramembranous ossification is the process by which mesenchymal cells differentiate directly into bone producing cells. This process produces the bones that form the top and sides of the skull. The remaining skull bones and the bones of the limbs are formed by endochondral ossification. In this, mesenchymal cells differentiate into hyaline cartilage cells that produce a cartilage model of the future bone. The cartilage is then gradually replaced by bone tissue over a period of many years, during which the cartilage of the epiphyseal plate can continue to grow to allow for enlargement or lengthening of the bone.