Bone Remodeling Bone Remodeling Bones are remodeled continually

Bone Remodeling

Bone Remodeling • Bones are remodeled continually – Means that they are broken down, built back up, change in shape, etc • Bone remodeling is in response to 2 factors: – Calcium levels in the blood – The pull of gravity and muscles

Bone Remodeling: Calcium Levels • When calcium levels drop below homeostatic levels, your parathyroid gland releases parathyroid hormone (PTH) – This stimulates osteoclasts to break down bone to release calcium in the blood • When calcium levels are too high, calcium is deposited in the bone • This is how bones are storage organs!!

Bone Remodeling: Gravity and Muscles • The more weight-bearing exercises you do, the stronger your bones will be – This causes an increase in bone size • Bedridden patients and astronauts suffer from bone mass/atrophy from lack of stress on their bones

Balance • There is a balance between osteoclasts and osteoblasts • Predict: – What would happen if the osteoblasts were too good at their job? • Melorheostosis (remember this? ? ) – What would happen if the osteoclasts were too good at their job?

Gorham’s Disease • “Vanishing Bone Disease” • Osteoclasts are overproductive and bones are broken down faster than they are built • http: //www. youtube. com/watch? v=l. HN 3 Qwb m 86 Q