NCIt definition : Involuntary muscle tissue of the internal organs. It is composed of elongated muscle
cells or fibers that are not arranged in a striated pattern and form layers of muscle
tissue. The smooth muscle cells contain a contractile apparatus composed of thin and
thick filaments and a cytoskeleton composed of intermediate filaments.;
Alternative definition : CDISC: Primarily involuntary, non-striated muscle tissue of the internal organs and
blood vessels.;