smooth muscle

Smooth muscle is a type of non-striated muscle, found within the "walls" of hollow organs and elsewhere like the bladder and abdominal cavity, the uterus, male and female reproductive tracts, the gastrointestinal tract, the respiratory tract, the vasculature, the skin and the ciliary muscle and iris of the eye. The glomeruli of the kidneys contain a smooth muscle like cell called the mesangial cell. Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure and function.
See more at Wikipedia.org...

One of the three types of muscle tissue in the body (skeletal, smooth, cardiac). Generally forms the supporting tissue of blood vessels and hollow internal organs such as the stomach, intestine, and bladder. So named because of the absence of microscopic lines called "cross-striations" which are seen in the other two types.

Noun
1. a muscle that contracts without conscious control and found in walls of internal organs such as stomach and intestine and bladder and blood vessels (excluding the heart)
(synonym) involuntary muscle
(hypernym) muscle, musculus
(hyponym) myometrium
2. muscle tissue that does not appear striated under the microscope; has the form of thin layers or sheets
(hypernym) muscle, muscular tissue
(part-meronym) smooth muscle cell