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Muscular System Development

The muscular system develops from the mesoderm layer and consists of cardiac, smooth, and skeletal muscles. Muscle contraction, generated by actin and the motor protein, myosin, facilitates movement and drives physiologic processes including circulation, respiration, and digestion. Cardiac and smooth muscle tissues develop from local populations of mesenchymal cells, while skeletal muscles develop from mesoderm within the somites. Myogenesis begins within a somite when cells respond to growth factors and activate the expression of myogenic basic helix-loop-helix transcription factors (MyoD). These cells become committed muscle precursor cells, or myoblasts, which fuse to form multinucleated myotubes that consist of terminally differentiated muscle cells. Many of the molecular mechanisms that regulate embryonic muscle cell proliferation and differentiation are thought be reactivated during adult muscle regeneration. For example, Wnt signaling can induce satellite cell proliferation and myoblast fusion. Investigating the pathways and mechanisms that regulate embryonic muscular system development may further our understanding of myopathies such as muscular dystrophy.