The skeleton

The skeletal system is the body’s internal frame: about 206 bones in a typical adult, connected at joints, that give the body its shape, hold it upright against gravity, and provide rigid anchor points that muscles pull on to create movement. Without it, the body would have no defined form and no way to convert a muscle’s pull into a controlled motion like a step or a grip.

Beyond shape and movement, the skeleton has a second, less obvious job: protection. Bone is dense and rigid, so the body wraps its most vulnerable organs in a bony cage. The skull encloses and protects the brain. The rib cage shields the heart and lungs. The vertebrae of the spine form a bony tunnel around the spinal cord. In each case, a soft, critical organ sits inside hard, load-bearing bone.