Assertion: heart's atrium | /r/HasProperty | upper chamber
Facets:
Source sentences:
text: The structure that controls blood flow between the heart’s left atrium (upper chamber) and left ventricle (lower chamber).
text: An opening between the left and right atria (the upper chambers) of the heart.
text: A condition in which an extra electrical pathway connects the atria (two upper chambers) and the ventricles (two lower chambers).