A dilator muscle is a type of muscle that functions to widen or open a passage or structure in the body. These muscles are often found in areas such as the iris of the eye, where they help control the size of the pupil, allowing more or less light to enter. They play a crucial role in various physiological processes, including vision and circulation. In addition to the iris, dilator muscles can be found in other parts of the body, such as the airways and blood vessels. By relaxing and expanding, these muscles help improve airflow and blood flow, contributing to overall health and function.