Skeletal muscle is made up of a large number of muscle fibres, surrounded by a cell membrane called a sarcolemma (Fig 1).

Muscle fibres are surrounded by a system of tubules to allow the rapid transmission of the action potential around the muscle.

The muscle fibres are, in turn, made up of filamentous bundles that run along the length of the fibre called myofibrils.

These can be further subdivided into individual filaments, which have a thick and thin component. Each of these consists of a repeating unit known as a sarcomere.