Definition: A sphincter is a circular band of muscle that opens and closes a tubular opening. According to
Wikipedia, there are over 40 different sphincters in the human body. Examples include: your iris (pupil of the eye), your mouth, your esophogus or, going smaller, a bile duct in your liver. These circular bands of muscle may be
voluntary (you can control) or
involuntary (controlled by the body).
Many of the sphincters in the body regulate the movement of fluids, food, and waste in the body. If a sphincter loses its tone (strength) incontinence or reflux may be seen, as in the case of urinary sphincters or esophogeal sphincters, respectively. Less commonly, sphincters can spasm and constrict, causing often painful conditions, such as Sphincter of Oddi Dysfunction. For a medical article on this condition, please see this article (with diagrams) from the Johns Hopkins University Gastroenterology and Hepatology Resource Center.
Veterinary Glossary Index
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