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

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

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

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

F. Types of Fractures … Table 6.2.1

Table 6.2.2

Table 6.2.3

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 6.13.1

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 6.13.2

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 6.13.3

- (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 6.13.4

Homeostatic Imbalances STUDENTS DO Rickets Osteoporosis

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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

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.

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

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

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

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

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

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

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