sphinc·ter /ˈsfɪŋ(k)tɚ/
  括約肌
  sphinc·ter /ˈsfɪŋ(k)tɚ/ 名詞
  括約肌
  Sphinc·ter n.  Anat. A muscle which surrounds, and by its contraction tends to close, a natural opening; as, the sphincter of the bladder.
  Sphinc·ter, a. Anat. Of, pertaining to, or designating, a sphincter; as, a sphincter muscle.
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  sphincter
       n : a ring of muscle that contracts to close an opening [syn: anatomical
           sphincter, sphincter muscle]