The Muscular System
While most people associate muscles with strength, they do more than assist in lifting heavy objects. The 650 muscles in the body not only support movement— controlling walking, talking, sitting, standing, eating and other daily functions that people consciously perform — but also help to maintain posture and circulate blood and other substances throughout the body, among other functions. Did you know you have more than 600 muscles in your body? They do everything from pumping blood throughout your body to helping you lift your heavy backpack. You control some of your muscles, while others — like your heart — do their jobs without you thinking about them at all. Muscles are all made of the same material, a type of elastic tissue (sort of like the material in a rubber band). Thousands, or even tens of thousands, of small fibers make up each muscle.You have three different types of muscles in your body: smooth muscle, cardiac muscle, and skeletal muscle.