fibrillar muscle

Fibrillar muscle, also known as striated muscle, is characterized by transverse dark and light bands. It is composed of elongated, often multinucleated fibers and includes skeletal, cardiac, and most arthropod muscles.1

Within fibrillar muscle, the myofibril is the fundamental structural and functional unit responsible for contraction. Myofibrils are cylindrical arrays of thick and thin filaments. The alternating overlap of these filaments creates the characteristic striated appearance. The region between two dark bands, known as a sarcomere, is the primary unit of muscle contraction. During contraction, these filaments slide past each other, increasing their overlap rather than shortening. Small structures called cross bridges on the thick filaments are believed to generate the force for this movement.234