ANATOMY

Detailed explanation-1: -Myofibrils are long contractile fibres, groups of which run parallel to each other on the long axis of the myocytes (long single multinucleated cells that combine to form the muscle).

Detailed explanation-2: -The sarcomere is the fundamental contractile unit of the myofibril. Z lines separate each sarcomere. The A bands, located at the center of each sarcomere, contain the thick filaments, which may overlap with thin filaments.

Detailed explanation-3: -The contractile proteins are myosin, the principal component of thick myofilaments, and actin, which is the principal component of thin myofilaments.

Detailed explanation-4: -Skeletal and cardiac muscle are referred to as striated muscle because of the visible organization of repeating units of contractile filaments, known as sarcomeres, into cylindrical bundles called myofibrils.

Detailed explanation-5: -A myofibril (also known as a muscle fibril or sarcostyle) is a basic rod-like organelle of a muscle cell. Skeletal muscles are composed of long, tubular cells known as muscle fibers, and these cells contain many chains of myofibrils.