What is a "sphincter"?

A sphincter is a muscular structure found in various locations throughout the body. Sphincters are ring-like muscles that encircle and control the opening and closing of certain passages or orifices in the body. They act as valves, regulating the flow of substances through these openings. Sphincters are essential for maintaining proper control and coordination of bodily functions such as digestion, urination, defecation, and the control of blood flow. They provide a barrier between different regions of the body and help prevent the backward flow of fluids or substances. Sphincters can be voluntarily or involuntarily controlled, depending on their location and function. Their presence and proper functioning are crucial for the normal functioning and regulation of various physiological processes.