Long bone development occurred through endochondral ossification. The current study investigated the main histological changes associated with the development of humerus from the New Zealand white rabbits. The upper limb or humerus during embryonic (12, 14, 15, 16, 18, 21, 24 and 27 days) and neonatal (3 and 7 days) development was processed for light microscopy. Three stages preceded endochondral ossification; limb bud (mesenchymal cells), cartilage primordia (mesenchymal condensation and differentiation into chondrocytes) and cartilage template (organization of chondrocytes into proliferative and hypertrophic zones) by 12, 14 and 15 days, respectively. At day 16, cartilage template elongated forming a cartilaginous diaphysis of the prospective humerus. At day 18, cartilaginous epiphyses were formed. Medullary cavity was established by day 21 with no signs of calcification in the bone collar. Primary ossification center appeared within the diaphysis at day 24 of embryonic development. Secondary ossification centers were seen within the epiphyses by day 3 of neonatal development. Two types of cartilage canals were investigated; short epiphyseal canals appeared from day 21 and long transphyseal canals appeared from day 27. At day 7 of neonatal development, the cartilage of the humerus was limited in two places; articular epiphyseal growth cartilage between articular surface and secondary ossification center, epiphyseal physeal growth cartilage between the secondary and primary ossification centers. The current study summarized the main histological stages of development of rabbit humerus. These results should be considered in molecular studies of endochondral bone formation.
Ahmed, Y. A., Abdelrahim, E. A., & Khalil, F. (2015). Histological Sequences of Long Bone Development in the New Zealand White Rabbits. Journal of Biological Sciences, 15(4), 177.