| one of the two organs in the back of the abdominal cavity that excrete urine, regulate fluid and electrolytes, and act as endocrine glands |
| either of two flat, triangular bones, each forming the back part of a shoulder; a shoulder blade |
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. |