Myofibril structure

The structure of the myofibril

The myofibrils contain the contractile apparatus of the muscle. These are called myofilaments and are divided into thick and thin filaments.

The thick filament is mainly composed of hundreds of myosin molecules. The thin filament consists of two chains of actin molecules helically intertwined. Also present on the thin filament are the regulatory proteins troponin and tropomyosin.

The myofibril has a very regulated structure with alternating light and dark bands. The repeating unit of the myofibril is known as the sarcomere.