atrium cordis vs atrium of the heart

atrium cordis and atrium of the heart both are nouns.

Word	Noun	Adjective	Verb	Adverb
atrium cordis	Yes	No	No	No
atrium of the heart	Yes	No	No	No

As nouns, atrium cordis and atrium of the heart are synonyms defined as:

atrium cordis and atrium of the heart: the upper chamber of each half of the heart

atrium cordis (noun)	atrium of the heart (noun)
the upper chamber of each half of the heart	the upper chamber of each half of the heart