Fig. 2- 2. Diagrams of the development of a long bone. A, Cartilaginous model. B, Bone collar. C, Vascular invasion of bone collar and cartilage. D, Endochondral ossification begins. E, Cartilaginous epiphyses begin to be vascularized (arrows). F, An epiphysial center of ossification appears. G, An epiphysial center begins in the other end. H, Two epiphysial discs are evident. I, The last (second) epiphysial center to appear fuses first with the shaft. J, The first epiphysial center to appear (where most growth in length occurs) fuses last with the shaft. Click for high resolution image.