Emergency!
Although bones are very strong, a powerful blow can break them. Unfortunately, it looks like that’s what happened when you hit the pavement. But not to worry—bones are amazing masters of self-repair.
While a neighbor calls your parents and 911, your broken bone calls for help too. Blood from broken blood vessels inside the bone causes swelling and signals the body’s repair centers. Meanwhile, an ambulance crew rushes you to the hospital emergency room.
At the hospital, a technician takes an X-ray photograph of your arm. X-rays are a high-energy form of light that passes right through soft tissue (such as muscles), but not bone. This lets doctors see the break so
