Bend the arm to see why muscles must work in pairs, then explore the three big jobs the skeleton does for your body.
Biceps
Triceps
Elbow
Check yourself
Why must muscles work in antagonistic pairs?
A muscle can only pull as it contracts, it cannot push. So a second muscle is needed to pull the bone back the other way. The biceps bends the elbow and the triceps straightens it.
What joins a muscle to a bone, and what joins a bone to another bone?
A tendon joins muscle to bone. A ligament joins bone to bone at a joint.
Name the three main jobs of the skeleton.
Support (holding the body up and giving it shape), protection (the skull guards the brain, the rib cage guards the heart and lungs), and movement (bones act as levers for muscles to pull on at joints).