1. Bone Growth Notes

2. Ossification Process of bone formation 2 types: Intramembranous
Occurs directly in connective tissue membranes
Flat bones of skull, mandible & clavicles
Fontanels – soft spots – still membrane

4. Endochondral
In embryos, skeleton is primarily hyaline cartilage
During development, much of this cartilage is replaced by bone
Most bones form this way

7. Bone Growth
Epiphyseal plates allow for growth of long bone during childhood
New cartilage is continuously formed
Older cartilage becomes ossified
Cartilage is broken down
Bone replaces cartilage

9. Appositional growth – growth in thickness; new bone added by periosteal osteoblasts

10. Types of Bone Cells Osteocytes Mature bone cells Osteoblasts
Bone-forming cells
Osteoclasts
Bone-destroying cells

11. Remodeling Bone is continually being broken down & changed (reformed)
Balance between actions of osteoclasts and osteoblasts

12. Hormonal Control Growth hormone : produced by pituitary gland
Thyroid hormone – stimulates epiphyseal plate closure
Not enough, affects growth
Plate closer = stops growth

13. Testosterone and estrogen
Plate closure
Osteoporosis in old age
Calcitonin – secreted by thyroid – inhibits osteoclasts and stimulates osteoblasts – decrease blood Calcium

14. Parathyroid hormone – stimulates osteoclasts and increased blood calcium