Ch. 6 … ** Need x-rays of fractures **

6.4 … E. Bone Remodeling - When: % annually in an adult -Function: 1) 2) 3) - Importance of Calcium  Nerve  Muscle  Blood Clotting  Cell division REMODELING: CONTINUED SLIDE 10

F. Types of 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  Closed Reduction  Open Reduction  Immobilization  The Body’s Process of Repair

G. Bone Repair The Body’s Process of Repair 1. Fracture Hematoma (immediate – 1 st day or 2)  Hemorrhage  Hematoma  Bone cells die Figure

G. Bone Repair … 2. Internal Callus of Fibrocartilage (few days – 1-2 weeks)  Chondroblasts produce: 3. External Callus  Chondrocytes and Osteoblasts: Figure

Repair … 3. Bony callus of Spongy Bone - few weeks – 2 to 3 months  Osteoblasts:  Internal and External Calli:  Spongy bone:  Compact bone: Figure

Repair … 4. Bone remodeling - (up to several months after bony callus)  Excess material:  Compact bone: Figure

6.6 Exercise, Nutrition, Hormones, and Bone Tissue A. Exercise and Bone Tissue 1. Mechanical Stress  Affects of Gravity  Exercise 2. Typical Effects produced in different types of bones: a) Long Bones  Thickest midway along shaft (↑ stress)  Thinnest in center b) Curved bones:  thickest where most likely to buckle c) Trabeculae: form along lines of stress d) Large, bony projections: occur where heavy, active muscles attach

B. Nutrition and Bone Tissue 1.Vitamin D 2.Calcium 3.Magnesium 4.Fluoride

1. Hormones That Influence Osteoblasts a) Infancy & Childhood:  growth hormone  Thyroid Hormone regulates growth hormone b) During puberty:  Testosterone and  Estrogens:  Promote adolescent growth spurts  Cause masculinization & feminization  Then induces epiphyseal closure– end growth C. Hormonal Regulation of Bone Growth

Control of Remodeling … 2. Hormones That Influence OsteoclastsControls - Function: in Modeling and Determines When Remodeling Occurs - Negative Feedback Loops  Stimulus =  Receptors & Control Center =  Effectors = a) Parathryroid Hormone  Parathyroid Glands  Primary control  PTH increases  Activates Osteoclasts  ________  PTH decreases  __________  __________  Stimulus to increase PTH =  Stimulus to reduce PTH =

b) Calcitonin  Much less involved  Thyroid

Homeostatic Imbalances  Rickets  Osteoporosis  30% of women over age (70% by 80); 20% men over 70  Makes bones fragile and fracture- prone– especially spongy bone  Often results in vertebral collapse (broken hips)  Risk Factors– page 193  END

Osteoporosis: Treatment  Bone reabsorption outpaces formation of Bone  Calcium and vitamin D supplements  Increased weight-bearing exercise  Hormone (estrogen) replacement therapy (HRT) slows bone loss  Increased risk of cancer and cardiovascular disease  Drugs: Biophophonates (↓ osteoclast activity), Selective Estrogen Receptor Mondulators (+, No – of estrogen), and Statins (↓ cholesterol & increase bone mineral density)

H. Calcium Homeostasis  Calcium only from the Diet 1. Hypocalcemia  Regulated by Vitamin D and PTH  PT Gland Cells have receptors for Calcium a) When Calcium is not bound, PTH is released and bone resorption occurs  PTH also causes  Ca reabsorption from urine  And stimulates production of Vitamin D  Which causes Ca absorption from intestines b) Blood Ca returns to normal and Ca binds to receptors on cells of PT Gland 2. Hypercalcedmis  Calcitonin released from Thyroid Gland

END

ab Participating... 2b. Why do exercisers have denser and stronger bones? A.Bones develop over longer time periods in exercisers B.Bone remodeling adds bone tissue to compensate for the stress of exercise C.Exercisers need more calcium for their muscles 2a. List 2 reasons why bones are remodeled in adults? Regulate blood calcium, compensate for stress, also to repair fractures, renew matrix

Participating… 4. Which of the following might help delay or even prevent the effects of osteoporosis? Why? A.Being sure to include plenty of calcium in the diet. B.Getting regular exercise. C.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 Falling blood Ca 2+ levels Calcium homeostasis of blood: 9–11 mg/100 ml Imbalance Figure 6.11

Hormonal Control of Blood Ca – raising Ca concentration Parathyroid glands release parathyroid hormone (PTH) Thyroid gland Parathyroid glands Falling blood Ca 2+ levels Calcium homeostasis of blood: 9–11 mg/100 ml Imbalance Figure 6.11

Hormonal Control of Blood Ca – raising Ca concentration Parathyroid glands release parathyroid hormone (PTH) Thyroid gland Parathyroid glands Falling blood Ca 2+ levels Calcium homeostasis of blood: 9–11 mg/100 ml PTH Imbalance Figure 6.11

Hormonal Control of Blood Ca – raising Ca concentration Parathyroid glands release parathyroid hormone (PTH) Thyroid gland Parathyroid glands Osteoclasts degrade bone matrix and release Ca 2+ into blood Falling blood Ca 2+ levels Calcium homeostasis of blood: 9–11 mg/100 ml PTH Imbalance Figure 6.11

Hormonal Control of Blood Ca – raising Ca concentration Parathyroid glands release parathyroid hormone (PTH) Thyroid gland Parathyroid glands Osteoclasts degrade bone matrix and release Ca 2+ into blood Falling blood Ca 2+ levels Calcium homeostasis of blood: 9–11 mg/100 ml PTH Figure 6.11

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