A skeletal muscle muscle consists of muscle fibres. One muscle fibre is approximatels 100 µm in diameter and consists of several nuclei and many mitochondria. Each muscle fibre contains myofibrils. These are approximately 1 µm in diameter.
The myofibril is organised in repating units called sacromeres. These contain thick and thin filaments. Muscle contraction occurs when the thin filaments slide along the thick filament by hydrolysing ATP  by what is known as the Sliding Filament Theory.
- ↑ Berg J., Tymoczko J and Stryer L. (2001) Biochemistry, 5th edition, New York: WH Freeman.