Le site de vulgarisation scientifique de l’Université de Liège. ULg, Université de Liège
sphincter

A circular muscle situated around a duct; by contracting, it makes it possible to close the duct. This contraction can be automatic (reflex) or voluntary. The human body contains several kinds of sphincters: around the anus, the urethra, but also the pylorus, for example, which at the base of the stomach interrupts the passage of food to the bowel.

© 2007 ULi�ge