Understanding Smooth Muscle: Found in Intestines, Bladder & Blood Vessels

The intestines, bladder, and blood vessels are made of smooth muscles. Smooth muscle is a type of involuntary muscle that is found in the walls of internal organs such as the stomach, intestines, and blood vessels. Smooth muscle cells are long and spindle-shaped, and they contain actin and myosin filaments, which are the same proteins that are found in skeletal muscle cells. However, smooth muscle cells are not arranged in sarcomeres, and they do not have the same striated appearance as skeletal muscle cells. Smooth muscle cells are also innervated by the autonomic nervous system, which means that they are not consciously controlled.

Smooth muscle is responsible for a variety of functions, including:

* Peristalsis: The rhythmic contraction and relaxation of smooth muscle cells that propels food through the intestines.

* Vasoconstriction: The narrowing of blood vessels, which increases blood pressure.

* Vasodilation: The widening of blood vessels, which decreases blood pressure.

* Urination: The emptying of the bladder.