Skeletal Muscle & Muscular Dystrophy: A Visual Approach

Abstract

Abstract Histologically, muscle is conveniently divided into two groups, striated and nonstriated, based on whether the cells exhibit cross-striations in the light microscope (Figure 3). Smooth muscle is involuntary: its contraction is controlled by the autonomic nervous system. Striated muscle includes both cardiac (involuntary) and skeletal (voluntary). The former is innervated by visceral efferent fibers of the autonomic nervous system, whereas the latter is innervated by somatic efferent fibers, most of which have their cell bodies in the ventral, motor horn of the spinal cord. Smooth muscle is designed to have slow, relatively sustained contractions, while striated muscle contracts rapidly and usually phasically. Both cardiac and smooth muscle cells are mononucleated, whereas skeletal muscle cells (fibers) are multinucleated. [In aging hearts or hypertrophied hearts, cardiac muscle cells are often binucleated.] Multinucleation of skeletal muscle arises during development by the cytoplasmic fusion of ...