The elucidation of Contraction of Skeletal Muscle is delivered in this Sqadia video. All skeletal muscles are composed of numerous fibers ranging from 10 to 80 micrometres in diameter. The sarcolemma is a thin membrane enclosing a skeletal muscle fiber. The sarcolemma consists of a true cell membrane, called the plasma membrane, and an outer coat made up of a thin layer of polysaccharide material that contains numerous thin collagen fibrils. Myofibrils are composed of actin and myosin filaments. Each muscle fiber contains several hundred to several thousand myofibrils. The thick filaments are myosin, and the thin filaments are actin. The myosin and actin filaments partially interdigitate and thus cause the myofibrils to have alternate light and dark bands. The ends of the actin filaments are attached to a Z disk. These bands give skeletal and cardiac muscle their striated appearance. The side-by-side relationship between the myosin and actin filaments is maintained by a large number of filamentous molecules of a protein called titin. These springy titin molecules act as a framework that holds the myosin and actin filaments in place. Also, in the sarcoplasm surrounding the myofibrils of each muscle fiber is an extensive reticulum called the Sarcoplasmic Reticulum.
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