Skeletal Muscles

Skeletal muscles are attached to the bones. They move the bones of the arms, legs, fingers, and other parts of the skeleton. We can consciously control the skeletal muscles, and so they are sometimes called voluntary muscles. The fibres that make up a skeletal muscle have alternate light and dark crossbands called striations.

One end of each skeletal muscle is attached to a bone that does not move when the muscle contracts. In most cases, the other end of the muscle is attached to another bone, either directly or by means of cordlike bundles of connective tissue called tendons. This second bone moves when the muscle contracts.

Muscles move the body only by pulling. They cannot push the tissues to which they are attached. Two sets of muscles therefore control most skeletal movements, such as the raising and then lowering of the forearm. One set of muscles pulls the bones in one direction, and the other set pulls the bones in the opposite direction. For example, one set of muscles pulls the forearm up, but it cannot push the forearm down. To lower the forearm, a second set of muscles must contract and pull it down.