HOW BONES MOVE
• Bones move with the help of joints.
• Joints cannot bring about movement without the help of muscles.
• Muscles bring about movement by contracting (shortening) and relaxing (lengthening).
• One end of a muscle is attached to a movable bone, whereas the other end is attached to a fixed bone.
• When the muscle contracts, it pulls the movable bone.
• Since muscles are only capable of pulling, they work in pairs.
• A pair of muscles 'biceps and triceps' helps us to move our arm.
• The muscles in our legs work in a similar manner.
• When arm is straightened, biceps relax (lengthens) while triceps contract (shortens).
• When arm is bent, biceps contract (shortens) while triceps relax (lengthens).
• The ends of the bones are covered with a tough, elastic tissue called cartilage.
• Cartilage makes the ends of the bones smooth and reduces friction between the bones during movement.
• Cartilage is also present in various other parts of our body.
• We could feel cartilage in the upper part of our ear and in the front part of our nose.
• These parts are not as hard as bones and can be bent.