1. Bone Development

2. Composition of Bone Approximately 33%-Organic  Collagen  Glycosaminoglycans (GAGs)  Contain Chondroitin sulfate  Resilience and toughness

3. Composition of Bone Approximately 66% Inorganic  Calcium phosphate (hydroxyapatite), calcium carbonate and magnesium phosphate  Hardness and rigidity  Radiopaque-xray cannot penetrate  Decalcify with acid—bone biopsies  Alkaline phosphatase plays a role in mineralization

4. Review the components Osteocytes Osteiod Lacunae Canaliculi

5. Review Osteoblasts  Form new bone  Periosteum and endosteum holds in reserve Osteoclasts  Bone destroying

6. Terms Ossification=true bone formation  Calcium deposited in osteoid matrix Calcification=calcium salts deposited in other tissue  Generally pathologic!!

7. Types of new bone formation Endochondral ossification=replacing fetal cartilage model with bone Intramembranous ossification=fibrous tissue infiltrated by osteoid tissue  Flat bones-i.e. skull

8. Intramembranous Ossification

9. Endochondral Ossification Cartilage pattern Ossification process starts in the midshaft  Replacing cartilage with bone  Osteoblast or osteoclasts? Ossification centers-primary (diaphysis) and secondary (epiphysis) Physis-proliferation of cartilage  Bone growth!

10. Ossification Centers Primary Ossification Center Secondary Ossification Center

11. Endochondral Ossification

12. What controls bone length growth?? Growth hormone  Stimulates release of insulinlike growth factors ( in liver and cells near growth plate)  Stimulate chondrocyte-increase cartilage production in epiphyseal cartilage Androgens (Testosterone> estrogen)  Ultimately, brings on epiphyseal closure  Stimulate ossification center vs. cartilage production

13. Mechanical Stress to bone Static vs. Dynamic load Stretch Compression Bending Torsion (twisting) Shearing

14. Remodeling Continuous turnover of bone in mature animals  Atrophy  Hypertrophy  Reshapes to minimize mechanical stress

15. Hormonal control of remodeling

16. Types of Fractures Simple vs. Open Fracture

17. Types of Fractures Greenstick fractures vs. Complete fracture

18. Types of Fractures Physeal fracture –young animals

19. Where are the fractures??

20. Types of Fractures Comminuted fractures

21. Fracture Repair Apposition and Immobilization Process  Clot formation  Granulation tissue  Periosteal and endosteal osteoblasts  Release osteoid to produce callus  Callus becomes ossified  Remodeling-osteoclasts remove excess

23. Callus formation

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