Muscles are what allow and make your skeleton able to move around. The muscles are attached to the bones by strips of dense connective tissue called tendons. The origin is one end of the muscle which remains stationary during a muscle contraction. This gives the muscle something to pull against. The insertion is the other side of the muscle, it is attached to a bone that moves when the muscle contracts. A muscle's insertion always moves towards its origin. Flexors cause the limbs to bend at a joint, while extensors cause them to straighten. …
