Growth of the long bones continues into early adulthood and is maintained by FGF-dependent proliferation of chondrocytes in the growth plates (long bones have two growth plates, in smaller bones (phalanges), there is only one at the tip).Chondrocytes toward the shaft (diaphysis) undergo hypertrophy and apoptosis as they mineralize the surrounding matrix.Blood vessels invade the center of the model, where osteoblasts localize, and proliferation is restricted to the ends (epiphyses).Chondrocytes form a model of the prospective bone.
Development of limb bones is via endochondral ossification ( Peripheral nerve elements, of course, are derived from neural crest)
Dermatome gives rise to connective tissue of the dermis.Limb elements arise from paraxial ( somitic) and lateral plate mesoderm Click here to launch the Simbryo Limb Development animation (and some really trippy music -you'll understand once the window opens.)
