Skeletal muscle is the single largest tissue mass in the body, constituting 40% to 45% of the dry body weight.
Muscles attach to the bones and produce movements or exert static forces. They can be connected directly to bone or insert on a bone by means of a tendon, which is a specialized type of connective tissue. The area of interface between a skeletal muscle and its tendon is called the musculotendinous junction.
Skeletal muscles may take a variety of forms, from the slender sartorius to the broad, fan-shaped pectoralis major. However, their histologic architecture remains the same. Each muscle is composed of muscle fibers called myofibers (Fig. 1).
Each of these fibers is essentially one large multinucleated cell created from the fusion of many other cells. An individual muscle fiber typically spans part of the muscle, though it may run its entire length.
A framework of connective tissue sup- ports muscle. Each fiber is surrounded by an endomysium. Groups of fibers are surround- ed by a perimysium, resulting in fascicles that are often large enough to be visible to the naked eye. The entire muscle is enveloped by an epimysium. This architectural arrangement supports integrated motion among the fibers.
Tendons allow the force generated by the muscle to be transferred into motion by connecting the skeletal muscle to the bony skeleton.