HENNING DALHOFF / SCIENCE PHOTO LIBRARY HENNING DALHOFF / SCIENCE PHOTO LIBRARY
Muscle fibre anatomy. Illustration showing the structure of human muscles from the macroscopic (centre) to the microscopic (far right) levels. A skeletal muscle (red) is shown attached to a bone. The muscle consists of muscle bundles (fascicles). Each fascicle consists of muscle fibres, which are shown here with nerves (blue) enervating them. The fibres consist of myofibrils, and the smallest element are the myofilaments within the myofibrils, consisting of the proteins actin (green) and myosin (blue). It is the movement of these overlapping protein strands that causes muscle contraction.
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