midriff vs muscle system

midriff and muscle system both are nouns.

Word	Noun	Adjective	Verb	Adverb
midriff	Yes	No	No	No
muscle system	Yes	No	No	No

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

midriff: (anatomy) a muscular partition separating the abdominal and thoracic cavities; functions in respiration
muscle system: the muscular system of an organism

Other hypernyms of midriff include membrane, tissue layer, muscular structure, musculature.

midriff (noun)	muscle system (noun)
(anatomy) a muscular partition separating the abdominal and thoracic cavities; functions in respiration	the muscular system of an organism
the middle area of the human torso (usually in front)