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Chapter 6: Osseous Tissue and Bone Structure

Chapter 6: Osseous Tissue and Bone Structure. 1. 2. Cells of Bone. Osteoprogenitor -precursor to osteoblast Osteoblasts -produce bone matrix Osteocytes -trapped osteoblast Osteoclasts -dissolve bone matrix. 3. Compact Verses Spongy Bone. 4. Long Bone Structure. 5.

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Chapter 6: Osseous Tissue and Bone Structure

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  1. Chapter 6: Osseous Tissue and Bone Structure 1

  2. 2

  3. Cells of Bone • Osteoprogenitor -precursor to osteoblast • Osteoblasts -produce bone matrix • Osteocytes -trapped osteoblast • Osteoclasts -dissolve bone matrix 3

  4. Compact Verses Spongy Bone 4

  5. Long Bone Structure 5

  6. Flat Bone Structure 6

  7. Ossification • Endochondrial • Intramembranous 7

  8. Intermembranous • Typical of flat bones • Ossification of mesenchymal cells 8

  9. Endochondral Ossification • Long bones • Hyaline cartilage breaks down 9

  10. Postnatal Bone Growth • Interstitial growth: • Increase bone length (adolescence) • Appositional growth: • Increase thickness and remodeling of all bones 10

  11. Epiphysial Plate 11

  12. 12

  13. Bone Growth • Growth hormone stimulates cell division • Thyroid hormone modulates growth hormone • Testosterone and estrogens (at puberty) • Promote adolescent growth spurts • End growth by inducing epiphyseal plate closure 13

  14. 14

  15. Bone Resorption • Osteoclasts secrete • Lysosomal enzymes (digest organic matrix) • Acids (convert calcium salts into soluble forms) • Dissolved matrix is transcytosed across osteoclast, enters interstitial fluid and then blood 15

  16. Control of Remodeling • What controls continual remodeling of bone? • Hormonal mechanisms that maintain calcium homeostasis in the blood • Mechanical and gravitational forces 16

  17. Bone Remodeling • Balance between resorption and formation 17

  18. Bone remodeling Bone growth Articular cartilage Cartilage grows here. Epiphyseal plate Cartilage is replaced by bone here. Bone is resorbed here. Cartilage grows here. Bone is added by appositional growth here. Cartilage is replaced by bone here. Bone is resorbed here. Figure 6.11

  19. Hormonal Control of Blood Ca2+ • Calcium is necessary for • Transmission of nerve impulses • Muscle contraction • Blood coagulation • Secretion by glands and nerve cells • Cell division 19

  20. Hormonal Control of Blood Ca2+ • Primarily controlled by parathyroid hormone (PTH) • Calcitonin has minor role • Leptin influences bone remodeling 20

  21. Exercise and Bones • Builds stronger bone • Inactivity leads to weak bones • Astronauts shrink as much as 4 inches 21

  22. Bone Repair 22

  23. Homeostatic Imbalances • Heterotrophic Bones -abnormal bone formation • Tendons, joints, kidneys, testes, sclera of the eye • Fibrodysplasia Ossificans Progressiva • Dwarfism -pituitary failure • Acromegaly -bone/cartilage thickening along facial contours • Gigantism -growth hormone overproduction • Marfan Syndrome -excessive cartilage at epiphyseal plates • Rickets -vitamin D deficiency • Paget's disease • Osteoporosis 23

  24. Osteoporosis 24

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