1. Chapter 6 … III. Bone Formation and Development … E
Chapter 6 … III. Bone Formation and Development … E. Hormonal Regulation of Bone Growth In Children
1. Infancy & Childhood:
Growth Hormone:
Thyroid Hormone:
2. During puberty: Test. and Estrogens:
 adolescent growth spurts
induces epiphyseal closure– end growth

2. F. Bone Remodeling in Adults - When:
- Amount: 5-10% annually in an adult
Function: 1) 2) 3)
1. Importance of Calcium
Nerve
Muscle
Blood Clotting
Cell division

3. Control of Remodeling … 2. Hormones That Influence Osteoclasts Controls
- Affected by Ca+ blood levels
- Negative Feedback Loops
Parathryroid Hormone– determines when to remodel
Parathyroid Gland cells: If low blood Ca+2, PTH increases  Activates Osteoclasts  Ca+2 blood levels increase
b) Calcitonin
Much less involved
Functions in oposition to PTH
3. Where to Remodel: determined by mechanical stresses
Gravity
Exercise
4. Other Factors: UV light & Vitamine D

4. IV. Bone Repair- Fractures
Classification by complexity, location, and other features:
Closed (Simple) vs. Open (Compound):
Completeness of break:

5. F. Types of Fractures …
Table 6.2.1

6. Table 6.2.2

7. Table 6.2.3

8. G. Bone Repair Treating Fractures Reduction = realignment
Immobilization
The Body’s Process of Repair
1. Fracture Hematoma (immediate – 1st day or 2)
Swollen
Painful
Inflamation
Figure

9. 2. Fibrocartilage Callus (few days – 1-2 weeks) New capillaries grow
G. Bone Repair …
2. Fibrocartilage Callus
(few days – 1-2 weeks)
New capillaries grow
Phagocytes clean up the dead
Fibroblasts & osteogenic cells come in and collagen fibers are produced to span the break
Chondrocytes develop and produce fibrocartilage
Externally bulging cartilage matrix forms
Figure

10. 3. Bony callus of Spongy Bone - few weeks – 2 to 3 months
Repair …
3. Bony callus of Spongy Bone
- few weeks – 2 to 3 months
Osteoblasts begin forming spongy bone that invades cartilage
Figure

11. - (up to several months after bony callus)
Repair …
4. Bone remodeling
- (up to several months after bony callus)
Excess material on outside and inside removed
Resembles original with slight bulge
Figure

12. Homeostatic Imbalances STUDENTS DO
Rickets
Osteoporosis

13. END

14. Participating . . .
2a. List 2 reasons why bones are remodeled in adults?
Regulate blood calcium, compensate for stress, also to repair fractures, renew matrix
2b. Why do exercisers have denser and stronger bones?
Bones develop over longer time periods in exercisers
Bone remodeling adds bone tissue to compensate for the stress of exercise
Exercisers need more calcium for their muscles
Figure 5.3: Osteoporosis. (a) Normal bone tissue. (b) After the onset of osteoporosis, replacements of mineral ions lag behind withdrawals. In time the tissue erodes, and the bone becomes hollow and brittle. a b

15. Participating…
4. Which of the following might help delay or even prevent the effects of osteoporosis? Why?
Being sure to include plenty of calcium in the diet.
Getting regular exercise.
Resting bones as often as possible.

16. Participate: 3. List 4 steps of bone repair.
1. Hematoma (blood-filled swelling) is formed
2. Break splinted by fibrocartilage to form a callus
3. Fibrocartilage callus replaced by a bony callus
4. Bony callus is remodeled to form a permanent patch
Hematoma
External callus
Bony callus of spongy bone
Healed fracture
New blood vessels
Internal callus (fibrous tissue and cartilage)
Spongy bone trabecula
Hematoma formation
Fibrocartilage callus formation
Bony callus formation
Bone remodeling

17. Hormonal Control of Blood Ca – raising Ca concentration
Imbalance
Calcium homeostasis of blood: 9–11 mg/100 ml
Falling blood
Ca2+ levels
Imbalance
Figure 6.11

18. Hormonal Control of Blood Ca – raising Ca concentration
Imbalance
Calcium homeostasis of blood: 9–11 mg/100 ml
Falling blood
Ca2+ levels
Imbalance
Thyroid
gland
Parathyroid
glands
Parathyroid
glands release
parathyroid
hormone (PTH)
Figure 6.11

19. Hormonal Control of Blood Ca – raising Ca concentration
Imbalance
Calcium homeostasis of blood: 9–11 mg/100 ml
Falling blood
Ca2+ levels
Imbalance
Thyroid
gland
Parathyroid
glands
Parathyroid
glands release
parathyroid
hormone (PTH)
PTH
Figure 6.11

20. Hormonal Control of Blood Ca – raising Ca concentration
Imbalance
Calcium homeostasis of blood: 9–11 mg/100 ml
Falling blood
Ca2+ levels
Imbalance
Thyroid
gland
Osteoclasts
degrade bone
matrix and release
Ca2+ into blood
Parathyroid
glands
Parathyroid
glands release
parathyroid
hormone (PTH)
PTH
Figure 6.11

21. Hormonal Control of Blood Ca – raising Ca concentration
Calcium homeostasis of blood: 9–11 mg/100 ml
Falling blood
Ca2+ levels
Thyroid
gland
Osteoclasts
degrade bone
matrix and release
Ca2+ into blood
Parathyroid
glands
Parathyroid
glands release
parathyroid
hormone (PTH)
PTH
Figure 6.11

22. Control of Remodeling … Response to Mechanical Stress
Surgical Neck- most common break point
Control of Remodeling … Response to Mechanical Stress
Determine WHERE remodeling occurs
Wolff’s law – bones remodel in response to stresses