retractor muscle vs musculus

retractor muscle and musculus both are nouns.

Word	Noun	Adjective	Verb	Adverb
retractor muscle	Yes	No	No	No
musculus	Yes	No	No	No

As nouns, musculus is a hypernym of retractor muscle; that is, musculus is a word with a broader meaning than retractor muscle:

retractor muscle: Any of various muscles that retract an organ or a body part.
musculus: one of the contractile organs of the body

Other hypernyms of retractor muscle include muscle.

retractor muscle (noun)	musculus (noun)
Any of various muscles that retract an organ or a body part.	one of the contractile organs of the body