Skeletal Muscles

Skeletal muscles are the muscles attached to the bones of the skeleton. A skeletal muscle is built from a large number of bundles called fasciculi, each wrapped in a connective-tissue sheath called the perimysium, and the whole muscle in turn is wrapped by an outer connective-tissue sheath called the epimysium or fascia. Each individual fasciculus is itself made up of many muscle fibres, called myofibres.

Each muscle fibre is a syncytial fibre — that is, it contains several nuclei within one continuous cell, formed by the fusion of many embryonic cells. The fibre's cell membrane is called the sarcolemma, which encloses the cytoplasm, or sarcoplasm. Because the sarcoplasm is packed with parallel, closely arranged myofibrils, the fibre's nuclei get pushed to the periphery of the cell. …