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The Muscular System Muscle tissue is one of the four basic tissue types that exist in the human body. There are three different muscle tissues: skeletal, cardiac, and smooth. They all have different organizations. Skeletal muscle tissue cells are long, cylindrical, striated, and have many nucleus. Cardiac muscle tissue, just like the skeletal is also in striations. However, these cells are short and branched. Unlike, the skeletal muscle tissue these cells die single nucliated. They are connected by intercolated discs. Smooth muscle tissue is not striated. Cells are short, spindle- shaped. Like the cardiac muscle it too is single nucleated. The T tubules in a cardiac muscle cell are short and broad and no trads. The T tubules encircle the sarcomeres at the Z lines rather than at the zone of overlap. The SR of a cardiac muscle cell lacks terminal cisternae. The appearance of an action potential triggers calcium release from the SR and contraction of sarcomeres like in skeletal muscle. Cardiac muscle cells are almost totally dependent on aerobic metabolism to obtain the energy needed to continue contracting. Cardiac muscle cell contractions last roughly 10 times longer than do those of skelet