Muscular system

- Muscle cells are found in every organ in the body and participate in every activity that requires movement. Together, they constitute nearly half of our body mass. The most obvious are the skeletal muscles that attach to the skeleton and give us strength and mobility. There are 3 types of muscles in our body: 1. Skeletal muscles: sculpt the body and contribute to our sense of attractiveness and well-being. Some of the smallest skeletal muscles control the focus of our eyes; some of the largest are responsible for the shivering that helps keep us warm when it is cold. 2. Cardiac muscles: Rhythmic contractions of the cardiac muscle of the heart pump blood throughout the body. 3. Smooth muscles: Powerful intermittent contractions of smooth muscle in the walls of the uterus propel the child through the birth canal. Slower waves of smooth muscle contractions push food through the digestive tract and transport urine from the kidney to the bladder. Steady, sustained contractions of smooth muscle in the walls of blood vessels regulate blood flow to every living cell in the body. Following are the major functions of the muscular system: 1. Movement of the body. Contraction of skeletal muscles is responsible for the overall movements of the body, such as walking, running, and manipulating objects with the hands. 2. Maintenance of posture. Skeletal muscles constantly maintain tone, which keeps us sitting or standing erect. We tend to think of muscles as producing movement, but another very important function of many muscles is to resist movement. The maintenance of posture while standing is a good example. If you faint, you collapse because you lose control over the muscles that support y