The skeleton comprises the first pa

The skeleton comprises the first part of the musculoskeletal system—the bones. There are 206 bones in the human body and they comprise the skeleton. The skeletal system is responsible for supporting the weight of the body, for posture, and for gait.Muscles comprise the second part of the system. They are responsible for most body movements. There are three main types of muscle—skeletal, smooth, and cardiac.Skeletal muscles are sometimes called striated muscles because of their striped appearance when seen under the microscope. They attach to bones of the skeleton and are under voluntary control. This allows us to engage in physical activities suchas walking, running, smiling, winking, and grasping. Skeletal muscles also allow us to manipulate things like holding a pencil or buttoning a shirt. Smooth muscles comprise the walls of organs such as the liver, spleen, and kidneys. They are responsiblefor the transport of nutrients and other materials through the body. Smooth muscles are not under voluntary control. We cannot make them work. Cardiac muscle is also involuntary. This particular type of muscle allows the heart to pump and accommodate (respond) to changes in the entire body that require it to pumpfaster or more slowly.