Skeletal muscle fibres. Coloured scanning electron micrograph (SEM) of a freeze-fractured bundle of skeletal (or striated) muscle fibres. The fracture planes across the fibres, and the removal of the sheath of connective tissue, has revealed the banding pattern that arises from the regular arrangement of the microscopic fibres (myofibrils) found in a muscle fibre. Skeletal muscle is under voluntary control. Magnification unknown.