1. Bone Remodeling

2. What is it? Bone breakdown & build-up
Happens throughout life (every bone in the body is COMPLETELY replaced every 7 years)
Most rapid after an injury—bone replaced totally within 1 year
Slows down after age 30
Also known as “bone metabolism”

3. Osteoclasts
“bone breakers”
Break down old bone

4. Osteoblasts
“bone sprouts”
baby bone cells

5. Osteocytes
“bone cells”
mature bone cells

6. Steps of Bone Remodeling
Step 1: Hematoma Formation
A hematoma is a “blood tumor” that forms at the site of the break
This painful, swollen area fills with blood from the broken blood vessels

7. Steps of Bone Remodeling
Step 2: Fibrocartilaginous callus formation
This is also called a “procallus” (before callus) or soft callus
Happens within one week
Connective tissue stem cells & capillary blood vessels penetrate
Phagocytes clear away junk
Cartilage and blood vessels start to form to create new bone

8. Steps of Bone Remodeling
Step 3: Bony Callus Formation
Takes several weeks to months
Osteoclasts break down fibrous cartilage
Osteoblasts lay new bone matrix, made of osteocytes
Bone is MOSTLY healed at this stage

9. Steps of Bone Remodeling
Step 4: Bone Remodeling
Compact bone replaces woven bone
Internal callus removed
Medullary cavity is restored