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Bone Resorption

Bone Resorption. The unique ability of self-renewal in bone tissue. Osteoclasts. Multinucleated bone cells (many nuclei). Function: to remove damage or old bone tissue by creating an acidic environment between bone surface and cell.

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Bone Resorption

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  1. Bone Resorption The unique ability of self-renewal in bone tissue

  2. Osteoclasts • Multinucleated bone cells (many nuclei). • Function: to remove damage or old bone tissue by creating an acidic environment between bone surface and cell. • Leaves behind an empty space within bone tissue known as a resorption pit.

  3. Osteoblasts • Mononucleated bone cells (single nucleus). • Function: to deposit a fresh bone matrix in the resorption pit left behind by the osteoclasts. • Responsible for the deposition of new bone.

  4. Osteocytes Lacuna- Space in which individual osteocytes reside within bone tissue. Canaliculus- Cellular protrusion which connect individual osteocytes with one another. Forms a communication network within bone tissue. • Osteoblasts which become stuck in the fresh bone matrix they have recently laid down. • Communication between osteocytes is vital for bone tissue health. • Disruptions within this communication network signals for bone to be remodeled or replaced.

  5. Summary of Bone Cells Osteoclasts Osteocytes Osteoblasts Osteoblast activity must equal osteoclast activity

  6. Remodeling • Why does bone need to be remodeled? • It has become hypermineralized (old) or had been damage. • How does bone know it needs to under go remodeling? • Disruption in osteocyte communicate initiates the process of bone remodeling. Steps of Bone Remodeling • Osteoclasts resorb bone. • Osteoblasts deposit fresh bone matrix • Osteoblasts become embedded within this matrix, transitioning into osteocytes. • Communication has been re-established.

  7. Bone Remodeling/Repair Local factors Blood Vessel Osteoclasts Lining cells Osteoblasts Microcrack Osteocyte apoptosis Cement line New bone Osteocytes Bone Animation: Bajaj D. Ph.D., adapted from http://courses.washington.edu/bonephys/physremod.html

  8. Osteoporosis • Osteoporosis is an age related skeletal disease. • Osteoporosis means “porous bone”. • About 10 million Americans are diagnosed with Osteoporosis, of which 80% are women.

  9. Osteoporotic Healthy Courtesy of Michael J. Klein, M.D. Fritton & Schaffler, 2008 “Bone Quality”

  10. Pharmaceutical Countermeasures of Osteoporosis • How can drugs alter this process of bone remodeling? • Bisphosphonates, which inhibits bone resorption (osteoclast activity). • Parathyroid Hormone, which stimulates bone formation (osteoblast activity).

  11. How do Bisphosphonates Function? Osteoclast Apoptosis Ruffled Border Absence of Ruffled Border Inhibition of Bone Resorption Animation by Bajaj, D. Ph.D.

  12. To think about: • Why is bone resorption vital to bone health? • What can happen if bone cell activity is not balanced? • How can drugs treat this imbalance in bone cell activity which is observed in Osteoporosis?

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