atrium

Plural: atria, atriums

Noun

• any chamber that is connected to other chambers or passageways (especially one of the two upper chambers of the heart)
• the central area in a building; open to the sky
• A central room or space in ancient Roman homes, open to the sky in the middle; a similar space in other buildings.
• A square hall lit by daylight from above, into which rooms open at one or more levels.
• A cavity, entrance, or passage.
• Any enclosed body cavity or chamber.
• An upper chamber of the heart that receives blood from the veins and forces it into a ventricle. In higher vertebrates, the right atrium receives blood from the superior vena cava and inferior vena cava, and the left atrium receives blood from the left and right pulmonary veins.
• A microscopic air sac within a pulmonary alveolus.
• A cavity inside a porate aperture of a pollen grain formed by the separation of the sexine and nexine layers, widening toward the interior of the grain.

Synonyms

cavaedium