A histological study of the developing condylar cartilage of the fetal mouse mandible using coronal sections.

The first indication of cartilage formation was detected on day 14.5 of pregnancy in close connection to the ossifying mandible. A separated blastema was never observed. Thus the findings support the concept that the condylar cartilage develops from already differentiated cells, not from primary undifferentiated mesenchymal cells. Moreover, endochondral bone formation started on day 16 of pregnancy. Although the condylar cartilage basically undergoes the same processes of endochondral bone formation as the long bone, many hypertrophic chondrocytes may survive and are released into the primary spongiosa.