Happy, retcopper?Quote from: cesium_133 on Jul 08, 2006, 04:38 AMFrom American Heritage Online Dictionary:
Sphincter:
>>A ringlike muscle that normally maintains constriction of a body passage or orifice and that relaxes as required by normal physiological functioning.<<
Basically, it's a round muscle that closes off an opening or hollow passage, within or on the outside of the body. When no longer required, it relaxes and allows for full function of said opening or passage.
The two most-known sphincters are the anal (which is the countermeasure one, and the one you employ to hold back a BM or urine) and the vaginal. There are others, though, including ones involving the heart, esophagus, and stomach.
And it's spelled sphincter...
