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Medical Term:

smooth muscle


one of the involuntary muscle fibers of the internal organs, blood vessels, and other body structures not under direct control of the will; contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei and a length of 20–200 mcm, or even longer in the pregnant uterus; although transverse striations are lacking, both thick and thin myofibrils occur; smooth muscle fibers are bound together into sheets or bundles by reticular fibers, and frequently elastic fiber nets are also abundant.

Synonym(s): unstriated muscle, unstriped muscle, visceral muscle

See Also: involuntary muscles

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