MICROANATOMY

Detailed explanation-1: -A sarcomere (Greek sarx “flesh", meros “part") is the smallest functional unit of striated muscle tissue. It is the repeating unit between two Z-lines. Skeletal muscles are composed of tubular muscle cells (called muscle fibers or myofibers) which are formed during embryonic myogenesis.

Detailed explanation-2: -The sarcomere is the smallest functional unit of a skeletal muscle fiber and is a highly organized arrangement of contractile, regulatory, and structural proteins. It is the shortening of these individual sarcomeres that lead to the contraction of individual skeletal muscle fibers (and ultimately the whole muscle).

Detailed explanation-3: -The smallest contractile unit of skeletal muscle is the muscle fiber or myofiber, which is a long cylindrical cell that contains many nuclei, mitochondria, and sarcomeres (Figure 1) [58].

Detailed explanation-4: -According to sliding filament theory of muscle contraction, the actin and myosin filament slide past each other with the help of cross bridge to reduce the length of the sarcomeres. The smallest unit of muscle contraction is a sarcomere(which is delineated by Z-lines).

Detailed explanation-5: -The portion of the myofibril between two successive ‘Z’ lines is considered as the functional unit of contraction and is called a sarcomere Sarcomere is considered as the functional unit of contraction in a muscle fibre. So, the correct answer is ‘Portion of a myofibril between two successive Z-lines’.