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Bone Metabolism

Bone Metabolism. Notes in Notebook But first let’s see if this helps… Bob and Claude??? http://www.youtube.com/watch?v=5gpysdG1HoE. Bone Metabolism. Bone stores 99% of total calcium in body Calcium ions involved with many body systems nerve & muscle cell function blood clotting

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Bone Metabolism

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  1. Bone Metabolism Notes in Notebook But first let’s see if this helps… Bob and Claude??? http://www.youtube.com/watch?v=5gpysdG1HoE

  2. Bone Metabolism • Bone stores 99% of total calcium in body • Calcium ions involved with many body systems • nerve & muscle cell function • blood clotting • enzyme function in many biochemical reactions

  3. Bone Homeostasis/Metabolism

  4. Details…Details…  G-protein activates adenylate cyclase to convert ATP to cAMP in the cytosol • G proteins (guanine nucleotid -binding proteins) Proteins involved in transmitting chemical signals outside the cell, and causing changes inside the cell They communicate signals from many hormones, neurotransmitters, and other signaling factors

  5. Bone Metabolism Background Info • The thyroid gland is located in the front of the neck and wraps around the trachea; has a shape that is similar to a butterfly formed by two wings (lobes) and helps to regulate metabolism

  6. Bone Metabolism Hormones • *Parathyroid hormone (PTH) is secreted if Ca+2 levels falls • PTH gene is turned on and more PTH is secreted from gland • osteoclast activity increased • kidneys retain Ca+2 so it is not all lost in urine and produces calcitriol • *Calcitriolis a hormone that works with PTH & promotes absorption of calcium in digestive tract & blood

  7. Bone Metabolism Hormones • *Calcitonin is a hormone that produces the opposite effects: • if calcium level gets too high • less absorption in the digestive tract, • increased excretion by the kidneys, • movement of calcium from the blood into the bones • inhibits osteoclast activity • increases bone formation by osteoblasts

  8. CONTINUED NOTES in Notebook: Important Bone Metabolism Vitamins • Vitamin A: Necessary for osteoclast activity • Vitamin C: Needed to build durable bone matrix (osteoid) • Vitamin D: Calcitriol is formed from vitamin D

  9. Bone HomeostasisBone Tissue and Exercise • Pull on bone by skeletal muscle and gravity is mechanical stress. • Lack of mechanical stress results in bone loss • reduced activity while in a cast or bedridden person • Weight-bearing exercises build bone mass

  10. Osteoporosis Prevention (or decrease in severity) • Calcium supplements, weight-bearing exercise, & hormone replacement therapy (including a form of calcitonin) • behavior when young may be most important factor!

  11. Bone Remodeling • Ongoing process • Osteoclasts secrete enzymes and acids to break down bone • This releases calcium and other minerals of bone for resorption by blood • Osteoblasts rebuild osteons

  12. Bone Remodeling • Continual remodeling of bone matrix along lines of mechanical stress • The distal femur is fully remodeled every 4 months

  13. Fracture Repair • A fracture is break in a bone • STAGE 1 Inflammation) Repair starts with formation of fracture hematoma: damaged blood vessels produce clot, bone cells die • new capillaries grow into damaged area • STAGE 2 Repair) Callus (healing tissue) formation: • fibroblasts lay down collagen fibers • chondroblasts produce cartilage to span the broken areas of the bone

  14. Fracture Repair • Bone Formation: • osteoblasts secrete spongy bone that joins the broken areas of bone • lasts 3-4 months • Bone remodeling: • compact bone replaces the spongy in the callus • surface is remodeled back to normal shape

  15. Video Clip Principles of Fracture Healing http://www.youtube.com/watch?v=VZF3xicLtTw

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