Skeletal muscle. Coloured scanning electron micrograph (SEM) of a bundle of skeletal muscle fibres (dark red). This tissue, which is under voluntary control, is responsible for the movement of long bones. It is also known as striated muscle, because the regular arrangement of its contractile proteins forms a pattern of bands (just visible) across the fibres. Each fibre is normally surrounded by a connective tissue sheath (endomysium, grey). The outer fibrous sheath (pink, upper right) still partially covers the whole bundle. This outer sheath is called the perimysium. Magnification: x200 at 6x7cm size.