Muscle

You already know a great deal about muscle structure and function from anatomy, physiology, and kinesiology classes. Important here is the basic structure of skeletal muscles. In skeletal muscles, thousands of long, cylinder-shaped fibers called myofibers (muscle fibers) lie parallel to one another. Myofibers are made up of very fine fibers called myofibrils that run lengthwise and consist of even smaller structures called myofilaments. Each myofiber is encased in fascia called the endomysium. Groups of myofibers are bundled together into fascicles by sheets of fascia called the perimysium. Individual muscles are formed by groups of fascicles wrapped in fascia called the epimysium. The muscle’s layers of fascia merge at both ends of the muscle and thicken into tough tendons that attach the muscle to the connective tissue covering of the bone (the periosteum). At every layer of muscle, fascia wraps fibers, groups of fibers, and the entire muscle organ, and then weaves the muscle into tendon and to the connective tissue covering bone (Fig. 20-1).

<FIG20-1>

<BX20-1>

<TITLE>Concept Brief: Structure of Muscle

1. Myofilaments → myofibrils = myofibers (fascial wrap = endomysium)
2. Bundles of myofibers = fascicles (fascial wrap = perimysium)
3. Groups of fascicles = muscle (fascial wrap = epimysium)
4. Fascia merge at either end of muscle to tendons to attach muscle to bone

</BX>