Consists of over 600 named muscles<ref>Stoppard, 1988.</ref>. Muscles are classified into three types: smooth or involuntary, striated or voluntary, and cardiac.
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*''Smooth muscle'' is found in the linings of arteries, in the lining of the digestive system, and in various organs. Smooth muscle is also called "involuntary" muscle.
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Most smooth muscle, such as the lining of the stomach, is controlled by the sympathetic and parasympathetic nervous system. Some smooth muscles, such as the [[myometrium]] (smooth muscle of the uterus), act mostly in response to hormones.