Myofibrils are composed of which structural unit?

Myofibrils are composed of repeated structural units called sarcomeres. Sarcomeres are the basic contractile units found in striated muscle tissue, including both skeletal and cardiac muscles. Each sarcomere contains overlapping thick and thin filaments, which interact to facilitate muscle contraction.

Understanding the composition of myofibrils is essential in grasping how muscles function. Each myofibril is a long, thread-like structure bundled within a muscle fiber, and it consists of numerous sarcomeres lined up end to end. This organization allows for the coordinated contraction of the muscle when the sarcomeres shorten in response to stimuli.

While filaments (thin and thick) are found within the sarcomeres, they do not represent the structural unit of the myofibrils themselves. Tendons are connective tissues that anchor muscles to bones and do not form part of the myofibrillar structure. Therefore, the correct identification of sarcomeres as the structural unit of myofibrils highlights the foundational aspect of muscle anatomy and function.