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What is the Bone?

What is the Bone?. Connective tissue. Organic matrix (cells & proteins) Inorganic elements (calcium hydroxyapatite ). Modeling and Remodeling of Bone. The balance of bone formation and resorption determines skeletal mass.

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What is the Bone?

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  1. What is the Bone?

  2. Connective tissue • Organic matrix (cells & proteins) • Inorganic elements (calcium hydroxyapatite)

  3. Modeling and Remodeling of Bone The balance of bone formation and resorption determines skeletal mass.

  4. From the preadolescent years to the end of the second decade of life, bone size and bone mass increase rapidly. The peak bone mass attained by approximately 30 years. There is steady decrement in skeletal mass after 30 years.

  5. Factors effecting Bone mass • Genetic factors • Environmental factors: • Calcium and Vitamin D • Exercise • Smoking

  6. CALCIUM REQUIREMENTS • For pre-menopausal women 25-50 years old: 1,000-1,200 milligrams per day. • For pregnant or lactating women:1,500 milligrams per day • For men ages 25-65: 1,000 milligrams per day. • For all people (women and men) over age 65: 1,500 milligrams per day.

  7. Vitamin D

  8. Sources of Vitamin D • Sun light and ultraviolet light • Diet

  9. REQUIREMENTS • Variable and depends in part upon sun exposure • The Recommended Dietary Allowance (RDA) of vitamin D for adults through age 70 years is 600 IU • After 70 years RDA increases to 800 IU • For pregnant and lactating mothers RDA is 600 IU

  10. VITAMIN D DEFICIENCY • Impaired availability of vitamin D, secondary to inadequate dietary vitamin D, fat malabsorptive disorders, and/or lack of sun exposure • Impaired hydroxylation by the liver to produce 25-OH vitamin D • Impaired hydroxylation by the kidneys to produce 1,25-dihydroxyvitamin D • End organ insensitivity to vitamin D metabolites

  11. VITAMIN D DEFICIENCY • Lack of vitamin D activity leads to reduced intestinal absorption of calcium and phosphorus. • Persistent vitamin D deficiency leads to secondary hyperparathyroidism, which causes phosphaturia and demineralization of bones (osteomalacia in adults and rickets in children).

  12. OSTEOMALACIA Decreased mineralization of newly formed osteoid

  13. CLINICAL MANIFESTATIONS • Asymptomatic • Diffuse bone pain • Polyarthralgias • Muscle weakness, and difficulty walking • Fractures

  14. Diagnosis • Elevated Alkaline phosphatase • Reduced Serum calcium and phosphorus • Decrease 25-hydroxyvitamin D (calcidiol) <15 ng/ml • Elevated PTH • Osteopenia on X-ray • Bone biopsy

  15. Osteoporosis • Low bone mass with micro architectural disruption and fragility, resulting in an increased risk of fracture • Normal serum calcium and phosphorus • Decreased bone mass can occur because peak bone mass is low, bone resorption is excessive, or bone formation during remodeling is decreased.

  16. CAUSES • Hormone deficiency • Hormone excess • Immobilization • Genetic disorder • Tobacco/ alcoholism • Miscellaneous

  17. CLINICAL MANIFESTATIONS Osteoporosis has no clinical manifestations until there is a fracture

  18. DIAGNOSIS • bone mineral density (BMD) by Dual energy x-ray Absorptiometry (DXA) • CT scan of bones

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