“The sphincter at the entrance of the esophagus helps regulate the flow of food into the stomach.”

“The thin sheet of circular muscle of the iris which constricts the pupil of the eye is also known as a sphincter.”

“A thickened band at the caudal extremity of the inferior pharyngeal constrictor forms the upper esophageal sphincter, or cricopharyngeus muscle.”

“In the urogenital tract, there are sphincters at the exit from the bladder.”

“Muscular sphincters may exist anteriorly or posteriorly in the pharyngeal bulb.”

“This muscle thickens near the urethra to form the internal and external sphincters.”