Skeletal muscle

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Like cardiac muscle, skeletal muscle is part of the striated musculature and includes all muscles that can be controlled voluntarily. Skeletal muscle fibers can vary greatly in length and thickness and consist of many individual cells fused together. This is called a morphological syncytium, which explains why individual fibers can have up to 100 nuclei.

The striations, which are visible under light microscopy, result from the organized arrangement of actin and myosin filaments in the sarcomere, the smallest contractile unit of a muscle fiber. Sarcomeres strung together form a myofibril and numerous myofibrils together form a muscle fiber.

Each muscle fiber is surrounded by a connective tissue sheath, the endomysium. Several muscle fibers together are called fascicles and are surrounded by another layer of connective tissue, the perimysium. Lastly, the entire muscle is covered by the epimysium.

Watch the following two videos to learn more about skeletal muscle in general as well as the motor unit:

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Now, it is time to put this newly acquired knowledge to the test! Start off by taking our quiz on skeletal muscle:

Ready to take it a notch further? Move onto the next quiz to test yourself on the motor unit of skeletal muscle and its components:

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Browse atlas

Before delving into the histological appearance of skeletal muscles, let us review each structure in further detail in the image galleries below:

Ready to look at these structures under the microscope?