One entry found for atrium.

Main Entry: atri·um
Pronunciation: -tr-m
Function: noun
Inflected Form(s): plural atria /-tr- /; also atri·ums
: a chamber of the heart receiving blood from the veins and forcing it into a ventricle that in lung-breathing vertebrates (as frogs and human beings) is one of two chambers of which the right receives blood full of carbon dioxide from the body and the left receives oxygen-rich blood from the lungs but in gill-breathing vertebrates (as fishes) is only a single chamber

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