The skeletons of human babies have about 300 bones, but these soon fuse together as the baby grows and a human adult has only 206. This framework of bones supports our bodies. Our bones also allow us to move (think of the arm and leg bones) as well as protecting our organs. The skull is like a helmet which surrounds our brain, protecting it from knocks, and the breastbone and ribs form a protective cage around our heart and our lungs.