sphincterA circle of muscle surrounding a hollow viscera or body tube, usually near the outlet, that can temporarily prevent the movement of the contents of the tube. A sphincter may be a voluntary or involuntary muscle. For example, the pyloric sphincter regulates the flow of food from the stomach into the small intestine. Related category ANATOMY AND PHYSIOLOGYAlso on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History |