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Muscle facts for kids

Muscle is the fleshy tissue that controls the movement of our bodies. When we turn our heads, bend our arms, or pick up something, we use muscles.

These actions are all carried out by voluntary muscles - those under the conscious control of the brain. These are also called skeletal muscles, because they are attached to the skeleton, generally forming a bridge over a joint. The attachments are tough cords called tendons. When you want to move your arm, your brain sends a nerve signal to the arm muscles. These contract (shorten) and pull on the tendons which pull on the arm bones to which they are attached, and the arm moves.

Muscle facts for kids
The Achilles tendon joins the calf muscle to the bone of the heel. In movement, the bone acts as a lever operated by the muscle, just as levers are used to move heavy weights	A muscle may be made up of many large bundles of muscle fibers. Each bundle is composed of smaller bundles of fibers

Some muscles are involuntary (not under conscious control). They do such jobs as opening and closing the ducts of glands, churning food in the stomach and regulating the size of blood vessels. All muscles are composed of hundreds of fibers. Those of voluntary muscle are each about 1/250 of an inch thick and up to three inches long. They are marked with alternate light and dark bands. For this reason, voluntary muscle is also called striped muscle. The fibers of involuntary muscle have no markings, and so it is called smooth muscle. The fibers are also much smaller - only about 1/120 of an inch long and 1/4000 of an inch thick. The muscle of the heart - cardiac muscle - looks like striped muscle but functions like smooth muscle. Besides, to build up muscle it is necessary to eat correctly, by means of sports nutrition, for example

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