Bone development

1. BONE DEVELOPMENT By: Madiha Shams BDS 1 st Year , Dow University Of Health Sciences

2. BONE Bone is specialized, mineralized connective tissue consisting by weight of 33% organic matrix, 28% type l collagen, and 5% noncollagenous proteins, including osteonectin, osteocalcin, bone morphogenitic proteins, bone proteoglycan and bone sialoprotein. This organic matrix is permeated by hydroxypatite (Ca10 (PO4)6 (0H)2 ), which makes up the remaining 67% of bone.

3. COMPOSTION OF BONE

4. BONE FORMING CELLS OSTEOBLAST: * Uninucleated * Cuboidal and columnar in shape. * Forms bone 2. OSTEOCYTES: * Star-shaped cell * Most abundant cell found in compact bone. * Maintain bone (together with inactive osteoblasts lining cells) 3. OSTEOCLAST: * Large, Multinucleated * Resorb bone

5. Endochondral Bone Formation Chondroblasts develops in primitive Mesenchymal & form an early Perichondrium Cartilage model. The developing Cartilage model assumes the Shape of bone to be formed and a surrounding Perichondrium becomes identified.

6. Endochondral Bone Formation At the midshaft of the diaphysis the perichondrium becomes a p eriosteum through development of Osteoprogentor cells and Osteoblasts, producing a collar of Bone by Intramembrane ossification Calcium salts are deposited in e nlarging cartilage model. Blood vessels grow through the periostem and bone collar carrying Osteoprogenitor cell within them. These cells establish a primary ossification center Diaphysis.

7. Endochondral Bone Formation Bony trabeculae spread out from t he primary ossification center to occupy the entire diaphysis linking up with previously formed bone collar with now forms the cortical bone of diaphysis. At this stage the terminal Dub-shaped epiphysis are still composed of cartilage.

8. Endochondral Bone Formation At both of them (the presise t ime varies between long bones) secondary or epiphysal ossification c entre are established along with blood Vessels of mesenchymal cells which becomes Osteoprogentor cells and Osteoblast.

9. Endochondral Bone Formation

10. Intramembranous Bone Formation

11. Intramembranous Bone Formation COARSE WOVEN BONE: The bone is cellular and disorganized.

12. Intramembranous Bone Formation IMMATURE BONE: The bone is less cellular and slightly more organized, Some primary osteons are forming.

13. Intramembranous Bone Formation MATURE LAMELLAR BONE: The tightly packed osteons create an organized bone matrix; fewer cells and little loose connective are apparent. As remodeling of the bone in its mature state takes place, the periosteal bone surface becomes more regular and eventually will be covered with circumferential lamellae.