Confocal light micrograph of a section through fibres (purple) of skeletal muscle. Skeletal muscle attaches to joints and long bones, and is under the conscious control of the brain. It consists of parallel muscle fibres sheathed with a sugar-protein complex (red). The fibres themselves are composed of the proteins actin and myosin. Muscle fibres contract as the actin and myosin slide over one another. Cell nuclei are green.