2. What is Chondrogenesis? Chondrogenesis is the earliest phase of skeletal development, which involves: 1. mesenchymal cell recruitment and migration 2. condensation of progenitors 3. chondrocyte differention and maturation 4. results in the formation of cartilage and bone during endochondral ossification

3. How does chondrogenesis occur? Chondrogenesis is initiated by the differentiation of mesenchymal cells that arise from three sources: 1. neural space cells of the neural ectoderm that gives rise to craniofacial bones 2. the sclerotome of the paraxial mesoderm which forms the axial skeleton 3. the somatopleure of the lateral plate mesoderm which yields the skeleton of the limbs

5. Endochondral and intramembranous bone development

6. Diagram of endochondral ossification

9. What are Bone Morphogenetic Proteins? Bone Morphogenetic Protein comes from the family of secreted growth factors which forms a subgroup of molecules within the transforming growth factor β (TGF-β) superfamily.

14. F GF in developing Limb

24. Results

25. Control Day 2

26. BMP4 Day 2

27. FGF2 Day 2

28. PTH Day 2

29. Control Day 4

30. BMP4 Day 4

31. FGF2 Day 4

32. PTH Day 4

33. FGF and BMP signaling pathways

34. BMP action in chondrogenesis

35. Parathyroid hormone signaling