Smooth muscle (non-striated)

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Description:

Smooth muscle tissue consists of two types - visceral (single-unit) smooth muscle and multiunit smooth muscle. Visceral smooth muscle is the more common type. Visceral smooth muscle forms sheets with fibers connected to one another by gap junctions, while multiunit smooth muscle consists of individual fibers with its own motor nerve terminals and few gap junctions. Stimulation of one visceral muscle fiber results in the contraction of many adjacent fibers, while stimulus of a multiunit fiber causes contraction of that fiber only. Visceral smooth muscle forms the walls of small arteries and veins, the walls of stomach, intestines, uterus, and urinary bladder. Multiunit smooth muscle forms the walls of large arteries, the airways to the lungs, the arrector pili muscles, the muscles of the iris, and the ciliary body that adjusts the focus of the lens.