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Skeletal Muscle

The three types of muscle in the human body are cardiac muscle, smooth muscle, and skeletal muscle. Skeletal muscle is responsible for around 40 percent of the body's mass. Skeletal muscle however, is the only type of muscle that is voluntary. This means you mustfirst send a message to your brain and tell it to do something, then you brain tells your body what to do (Kimball).
The structure of skeletal muscle is not common to many other cells in the body. For one, muscle cells are multinucleated. This means that they have more than one nuclei. When speaking of muscle cells, the terms fiber and cell are used interchangeably. Because muscle fibers are not single cells, the parts are given different names.Muscle cells as seen from a microscope have a very unique shape. They appear to be elongated and striated in appearance (Kimball). The outermost layer of a muscle is the epimysium. According to the NDI Foundation's definition, this is a fibrous sheath around the entire muscle. Moving in from the epimysium is the perimysium. This connective tissue surrounds bundles of muscle fibers or cells. The bundles that the perimysium surrounds are called fasciculus. From there each of the individual muscle fibers are surrounded by a connective tissue called the endomysium. Each of the individual muscle fibers is a thin and elongated cylinder that in most cases extends as long as the muscle itself. The cell membrane of the muscle cell is called the sarcolemma. Below the sarcolemma is the sarcoplasm. The sarcoplasm is simply the cytoplasm of a muscle cell. In the sarcoplasm
there are cellular proteins, various organelles and myofibrils. Myofibrils are many thread-like structures that contain contractile proteins. The myofibrils are composed of either myosin or actin protein filaments. The way that the myosin and actin are arranged gives the muscle its striated appearance. Within the actin molecule there are the filaments troponin…

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