Skeletal (or striated) muscle consists of muscle fibers, which are long, cylindrical multinucleated cells with diameters of 10-100 μm. During embryonic muscle development, mesenchymal myoblasts (L. myo, muscle) fuse, forming myotubes with many nuclei. Myotubes then further differentiate to form striated muscle fibers. Elongated nuclei are found…[Read more]

Smooth muscle, also called involuntary muscle, muscle that shows no cross stripes under microscopic magnification. It consists of narrow spindle-shaped cells with a single, centrally located nucleus. Smooth muscle tissue, unlike striated muscle, contracts slowly and automatically. It constitutes much of the musculature of internal organs and the…[Read more]