Continuous process where bones are resorbed by osteoclasts and remade by osteoblasts. RANKL → initiates remodelingOsteoprotegerin → Turn off remodeling

Repairs tiny cracks due to normal activities.Help bones heal after a fracture.

Bone degradation:→ Osteoclasts sense microcracks and produce RANKL (receptor activator of nuclear factor κ ligand) → binds to RANK receptors on monocytes.→ Monocytes fuse to osteoclast cells.→ Osteoclasts secrete collagenase → digest collagen → drill pits known as Howship's lacunae→ Osteoclasts produce HCl which dissolves hydroxyapatite → Calcium and phosphate released in bloodstream

Bone resorption:- Osteoblasts secrete osteoprotegerin, which binds to RANKL and prevents it from activating RANK receptors → slows actiation of osteoclasts- Undergo apoptosis- Secrete osteoid seam to fill in lacunae → calcium and phosphate deposit on seam and form hydroxyapatite- Some osteoblasts become trapped in lacunae and turn into osteocytes

PTH promotes bone resorption.Calcitonin inhibits bone resorption.Mechanical stress causes high rate remodelling.Vitamin D decreases calcitonin → increased bone resorption.