fundus vs complex body part

fundus and complex body part both are nouns.

Word	Noun	Adjective	Verb	Adverb
fundus	Yes	No	No	No
complex body part	Yes	No	No	No

As nouns, complex body part is a hypernym of fundus; that is, complex body part is a word with a broader meaning than fundus:

fundus: (anatomy) the base of a hollow organ or that part of the organ farthest from its opening
complex body part: a particular complex anatomical part of a living thing and its construction and arrangement

Other hypernyms of fundus include anatomical structure, bodily structure, body structure, structure.

fundus (noun)	complex body part (noun)
(anatomy) the base of a hollow organ or that part of the organ farthest from its opening	a particular complex anatomical part of a living thing and its construction and arrangement