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, a⋅tri⋅ums. | 1. | Architecture.
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| 2. | Anatomy. either of the two upper chambers on each side of the heart that receive blood from the veins and in turn force it into the ventricles. |

a·tri·a (ā'trē-ə) n. A plural of atrium. |
sing. atrium (ay-tree-uhm)
The two upper chambers in the heart, which receive blood from the veins and push it into the ventricles. (See circulatory system.)
atrium a·tri·um (ā'trē-əm)
n. pl. a·tri·ums or a·tri·a (ā'trē-ə)
A chamber or cavity to which several chambers or passageways are connected.
Either the right or the left upper chamber of the heart that receives blood from the veins and forces it into a ventricle.
That part of the tympanic cavity that lies below the eardrum.
A subdivision of the alveolar duct in the lung from which the alveolar sacs open.
| atrium (ā'trē-əm) Pronunciation Key
Plural atria or atriums A chamber of the heart that receives blood from the veins and forces it by muscular contraction into a ventricle. Mammals, birds, reptiles, and amphibians have two atria; fish have one. |
atria
in vertebrates and the higher invertebrates, heart chamber that receives blood into the heart and drives it into a ventricle, or chamber, for pumping blood away from the heart. Fishes have one atrium; amphibians, reptiles, birds, and mammals, two
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