The role of cartilage in osteogenesis in the human fetal vertebral body.

The cartilage canals of the thoracic and lumbar vertebrae of fetuses ranging in crown-rump (C.R.) length from 33 to 180 mm were examined under light microscopy. The activity of the cells within these canals contributed to the anterolateral growth of the vertebral body. Bone formation was seen to commence in the center of the vertebral body. The cells of the connective tissue contained within the cartilage canals appeared to participate in the process of osteogenesis in multiple, discrete foci. In five-month-old fetuses, periosteal bone was noted on the anterior and posterior surfaces of the vertebral body, and calcification in the walls of the cartilage canals gave the histologic appearance of bone spicules.