midriff vs muscular structure

midriff and muscular structure both are nouns.

Word	Noun	Adjective	Verb	Adverb
midriff	Yes	No	No	No
muscular structure	Yes	No	No	No

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

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

Other hypernyms of midriff include membrane, tissue layer, muscle system, musculature.

midriff (noun)	muscular structure (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)