Skeletal muscle fibres. Light micrograph of a longitudinal section through muscle tissue, showing numerous long muscle fibres with repeating dark and light striations. These are the protein contractile filaments that occupy most of the fibre cytoplasm. Skeletal muscle fibres are the product of fusions of many individual muscle cells. Skeletal muscle fibres are therefore multi-nucleated with nuclei (dark ovals) located peripherally although they may appear to be central depending on the orientation in the sectioned tissue. This tissue sample is from a dog.