- a circular band of voluntary or involuntary muscle that encircles an orifice of the body or one of its hollow organs.
Origin of sphincter
Examples from the Web for sphincter
This sphincter opens automatically only in connection with the act of swallowing.Physiology
Ernest G. Martin
The sphincter is kept in a state of tonic contraction by a nervous centre situated in the lumbar portion of the spinal cord.
Thus, Jules Aron reports from the epidemic at Joigny a case of recovery after complete paralysis of the sphincter ani.
These are usually fibrous when situated below, or vascular when situated above, the sphincter ani muscle.
The sphincter ani is constantly in a state of tonic contraction, but the force of its contraction may be voluntarily increased.
- anatomy a ring of muscle surrounding the opening of a hollow organ or body and contracting to close it
Word Origin and History for sphincter
1570s, from Middle French sphincter, from Late Latin sphincter "contractile muscle," from Greek sphinkter "band, anything that binds tight," from sphingein "to squeeze, bind," of unknown origin. First used in anatomical sense by Galen.
- A ringlike muscle that normally maintains constriction of a body passage or orifice and that relaxes as required by normal physiological functioning.anatomical sphincter
- A ring-shaped muscle that encircles an opening or passage in the body. The opening and closing of the anus is controlled by contraction and relaxation of a sphincter, as is the opening that leads to the stomach from the esophagus.