Anat. a ring-shaped muscle that surrounds a natural opening in the body and can open or close it by expanding or contracting
Origin of sphincterLate Latin ; from Classical Greek sphinktēr ; from sphingein, to draw close ; from Indo-European an unverified form spheig- ; from base an unverified form spēi-, to flourish, grow thick from source speed, spare
A ringlike muscle that normally maintains constriction of a body passage or orifice and that relaxes as required by normal physiological functioning.
Origin of sphincterLate Latin sphinctēr, from Greek sphinktēr, from sphingein, to bind tight.