The muscular system supports the movement of the body, the circulation of blood, and the process of digestion. The muscular system works closely with the skeletal system, and together they form the musculoskeletal system.
Though there are hundreds of muscles in our bodies, they are all made of the same thing. A muscle is a type of elastic tissue that consists of many small fibers. Like a rubber band, un-exercised muscles are quite brittle. Their elasticity improves with constant use. This is why athletes and performers take such care during warm-ups and stretches.
There are three muscle categories: smooth, cardiac, and skeletal. Smooth muscles are involuntary muscles, meaning you can't make them move by thinking about it. You can find smooth muscles in your stomach and bladder. Cardiac muscles are so named because they make up the heart. Skeletal muscles are the most common variety, responsible for posture and movement.