How does the body constantly rebuild its own skeleton?

The answer

Bone remodeling is a continuous process in which old or damaged bone is removed and replaced with new bone tissue. Osteoclasts (bone-dissolving cells) secrete acids and enzymes that break down small areas of bone in a process called resorption, while osteoblasts (bone-building cells) follow behind, depositing new collagen matrix that is then mineralized with calcium and phosphorus. This cycle takes about 4 to 6 months per remodeling unit, and at any given moment roughly 10% of your skeleton is being actively remodeled. The entire adult skeleton is replaced approximately every 10 years. This process allows bones to repair microdamage, adjust their architecture in response to mechanical loading (Wolff's law), and serve as the body's calcium reservoir. After about age 30, resorption begins to slightly outpace formation, leading to gradual bone density loss.