Time And Order Of Appearance Of Ossification Centres Of The Rat Skeleton

Abstract

The time and sequence of ossification pattern of the skeletal system of the Rattus rattus were studied in serial whole mounts prepared from Day 10 to Day 21.5 (day of delivery). In the neurocranium, each bone is represent by a single ossification centra. At birth, the neurocranium is a well formed miniature of that in the adult. Four stages can be distinguished in the ossification of the vertebral column. All ossification centres in the vertebrae were found to be present at birth. In the appendicular skeleton, the chondrogenesis and osteogenesis patterns proceed in proximo-distal sequence with postero-anterior direction. It is possible to map limb part giving rise to each skeletal element as it appears. The pelvic limb bones are ossified later than those of the pectoral limb. Sexual dimorphism during ossification is not pronouced.