Expert Football > Training > Soccer Fitness > Muscles & Strength > Structure of the Muscles
Skeletal muscles
Skeletal muscles are made up of many fascicules, bundles of about 10 to 100 long cylindrical cells, surrounded by the perimysium. These long cells are called fibers and vary between 1 to 40 microns in length and 10 to 100 microns in diameter. That is considered a lot, keeping in mind that a standard body cell's diameter is about 10 microns and a strand of hair is about 100. Muscle fiber cells themselves are enclosed by the endomysium layer and contain cylinders of protein called myofibrils. Myofibrils have thin (made up of actin protein) and thick (made up of myosin protein) filaments, both running parallel along the long axis of the muscle fiber. Filaments in the myofibril are arranged in hexagonal pattern - each thick filament is encircled by six thin ones.
Z-bands (also called Z-disks or Z-lines) are structures (perpendicular to the filaments) that separate myofibrils into segments called sarcomeres. The thin actin filaments are anchored to the Z-bands at one end only. Their other end is just slightly overlapping the thick filaments who remain centered in a sarcomere.
