Osteogenic cellsor osteoprogenitor cells, which are undifferentiated precursor cells, respond to a stimulus such as bone injury or damage by dividing and differentiating into osteoblasts. 

Osteoblastsare bone-forming cells. They mature and give rise to other bone cells such as osteocytes and bone lining cells.  

Osteocytes monitor changes in stress and pressure that affect the bones, responding to every movement and change from small normal movements involved with using the body to more intense changes such as injuries. 

On sensing an injury, such as a damaged, cracked, or broken bone, osteoclasts activate and send signals to osteoclasts and osteoblasts to work on repairing the damaged bone tissue. On receiving the signal, osteoclasts resorb damaged bone tissue. This involves dissolving the area around the break. Osteoblasts then start laying down healthy new bone tissue in the spaces that need to be repaired and strengthened. The newly deposited bone matrix solidifies and hardens into new, healthy bone.