In reality, no one really knows how complicated the process of simply moving your arm up and down. Garenteed anybody's first time learning about the anatomy of our muscles and the microscopic structures will be mind blown. Imagine we are in the "Magic School Bus" (I always do), and we are in any skeletal muscle in your body. We "ride" from the bone to the tendon (made of epi-, peri- and endomysiums). Then we suddenly come across a new surface: a little less strong. The epimysium! Feeling adventurous, we venture deeper into the muscle. We come across the perimysium, the connective tissue that surrounds the fascicles. Deeper, we enter a fascicle (bundle of muscle fibers). The last of the mysiums, endomysium, surrounds each muscle fiber. In each muscle fiber, the myofibrils contain sacromeres. We are traveling to see the infamous actin and myosin in action! Entering the sacromere, we see layers and layers and layers of what we know as the thick and thin filaments. Specially designed to overlap, the thick filaments (myosin) bind to the thin (actin) and "slide" all the actin simultaneously, creating CONTRACTION!
After we leave the body, we notice the skeletal muscle contains all the mysiums (epi-,peri- and endo-). Why? After seeing how much work a simple movement takes, we realize that the muscle is responsible for movement of an entire bone! SOO therefore, the muscle needs to have all three mysiums for strength to make movement possible without tearing. Yeah. Our body is amazing.
