Do the muscles pull the structures, or push them? Explain briefly.

The muscles in the body provide the means of all movements. Muscles pull the structures. Each muscle usually has two ends- a fixed end where the muscle originates and a movable end which pulls some other part. The movable end is shorter and thicker and hence pulls the bone at the movable end. Muscles can only contract and relax, they cannot lengthen or elongate.
The movable end is projected out to form a tough structure referred to as a tendon which is attached to the bone. When a muscle is triggered by a nerve, contraction of the muscle occurs and it becomes thicker and shorter which causes the bone to be pulled at the movable end.