Skeletal muscle fibres. Coloured scanning electron micrograph (SEM) of a bundle of skeletal striated muscle fibres (myofibres), showing the myofibrils and transverse tubules. Muscles are composed of tubular cells called myocytes, also known as muscle fibres, and these cells in turn contain many chains of myofibrils. Skeletal muscles are responsible for the movement of the skeleton and organs such as the tongue and the globe of the eye. Magnification: x3150 when printed 10 centimetres wide.