Ossification of the Femur and Tibia of the Post-Hatching Japanese Quail

The current study aimed to describe the histological changes of the femur and tibia of the post-hatching quail. Femur and tibia from 1-day- to 6-weeks post-hatching quail were processed for light microscopy. Histological examination revealed that endochondral ossification was a delayed process in the development of femur and tibia preceded by periosteal ossification. Femur and tibia of 1-day-post-hatching quail consisted of growth cartilage enclosed in a tube of periosteal bone collar. The collar extended toward the epiphysis dividing it into articular cartilage proper and lateral articular cartilage. Down to the articular cartilage, there was a physeal growth cartilage, in which the chondrocytes were organized into resting, proliferative and hypertrophic zones. Focal areas of hypertrophic chondrocytes were observed in the epiphysis of the tibia but not of the femur, which acted as a nidus for formation of the secondary ossification centre after in 2-week-posthathcing quail. Primary ossification centre was seen in both femur and tibia after 2 weeks and ossification continued replacing the cartilage until the 6th week when only permanent articular cartilage remained. Cartilage canals were present in both femur and tibia starting from the day 1, but chondrified and completely disappeared after the 6th week. The current study suggests that the periosteal ossification preceded the endochondral ossification and plays an important role in quail long bones development.