The Skeleton
This provides a tough flexible framework.
It stores contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons (calcium and phosphorous).
It makes red blood cells, platelets and some white blood cells in the bone contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons.
It forms a system of levers, enabling contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons.
It contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons the internal organs.

Bone is continually broken down and rebuilt. Bone density can be increased by weight-bearing contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons, and contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons can make the bones less dense and weaker.

Joints and Movement
Bones meet at joints.
contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons hold bones together.
contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons attach muscles to bones.
Different types of joint allow different sorts of movement.
Most joints are synovial joints - they are lubricated with contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons fluid.

Muscles
Skeletal muscles can be moved at will. contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons impulses from the brain pass a signal to the muscle to make it contractexercisesinactivityLigamentsmarrowmineralsmovementNerveprotectssynovialTendons.
Muscles cannot push, they can only pull.
To move a bone back into place, another muscle has to pull it back.