sphincter vs sphincter muscle

sphincter and sphincter muscle both are nouns.

Word	Noun	Adjective	Verb	Adverb
sphincter	Yes	No	No	No
sphincter muscle	Yes	No	No	No

As nouns, sphincter and sphincter muscle are synonyms defined as:

sphincter and sphincter muscle: a ring of muscle that contracts to close an opening

Other synonyms of sphincter include anatomical sphincter.

sphincter (noun)	sphincter muscle (noun)
a ring of muscle that contracts to close an opening	a ring of muscle that contracts to close an opening