Muscles are constructed of bundles of fibers contained in protective sheaths, called fascia, which are then bundled together. The biggest bundle is the muscle itself. The next bundles in line are the fascicles, which contain the long, single-celled muscle fibers. Muscle fibers are then sub-divided into myofibrils, which are divided again into bundles of myofilaments, made up from chains of sarcomeres.
There are several important elements in the construction of our muscles: Epimysium - A layer of connective tissue that encases the entire muscle. Endomysium - A layer of connective tissue that covers the muscle fibers and also contains capillaries (tiny blood vessels) and nerves. Perimysium - A layer of connective tissue that bundles together between ten to several hundreds of individual muscle fibers into fascicles.