Smooth, or involuntary, muscle has no cross stripes under a microscope. Small spindle-shaped cells with a single nucleus form it.

Smooth muscle contracts automatically and gently. It makes up much of the organs’ and digestive system’s musculature. 3-10 m thick and 20-200 m long, smooth muscle cells. Myofilaments dominate the eosinophilic cytoplasm. The core’s nucleus becomes cigar-shaped during contraction.