—atrial, adj./ay"tree euhm/, n., pl. atria /ay"tree euh/, atriums.1. Archit.a. Also called cavaedium. the main or central room of an ancient Roman house, open to the sky at the center and usually having a pool for the collection of rain water.b. a courtyard, flanked or surrounded by porticoes, in front of an early or medieval Christian church. See diag. under basilica.c. a skylit central court in a contemporary building or house.2. Anat. 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. See illus. under heart.[1570-80; < L (in anatomical sense < NL)]
* * *In an ancient Roman house, an open central court that contained the impluvium, a basin where rainwater collected.It originally contained the hearth and functioned as the center of family life. The term later came to be used for the open front courtyard of a Christian basilica, where congregants collected before services. The atrium was revived in the 20th century in the form of glass-covered, greenery-filled multistory spaces sometimes found in shopping centers, office buildings, and large hotels.Atrium of the basilica of S. Ambrogio, Milan, 1088–1128AlinariArt Resource
* * *in architecture, originally an open central court of a Roman house and later of a Christian basilica. In domestic and commercial architecture the concept of the atrium experienced a revival in the 20th century.In Roman times the hearth was situated in the atrium. With the developing complexity of the domus (a more capacious residence), however, the kitchen and hearth were removed to other positions, and the atrium began to function as a formal reception room and as the official centre of family life. By the end of the Roman Republic, one or more colonnaded courts were added in the larger houses, removing from the atrium the last vestiges of family life. During the Roman Empire, the room virtually became the office of the owner of the house. Traditionally, the atrium held the altar to the family gods, the Lares. The atrium was designed either with or without columns; it had, universally, a marble basin known as the impluvium, which was situated in the centre of the room under the opening in the roof called the compluvium.The term atrium is used in a generic sense (like the English hall) for both consecrated and unconsecrated buildings such as the Atrium Vestae, where the Vestal Virgins lived, and the Atrium Libertatis, the residence of the Roman censor. In Rome the word atrium also signified any open court surrounded by porticoes placed in front of a temple. The concept of an atrium was also adopted by the early Christians. An open court, or atrium, surrounded by colonnades or arcades was often built in front of a Christian basilica. The churches of S. Clemente at Rome, S. Ambrogio at Milan, and the Basilica Eufrasiana of Parenzo (Poreč) in Istria (Croatia) still retain their atria.▪ heartin 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.In humans the atria are the two upper chambers of the heart. Each is roughly cube-shaped except for an ear-shaped projection called an auricle. (The term auricle has also been applied, incorrectly, to the entire atrium.) The right atrium receives from the veins blood low in oxygen and high in carbon dioxide; this blood is transferred to the right lower chamber, or ventricle, and is pumped to the lungs. The left atrium receives from the lungs blood high in oxygen and low in carbon dioxide; this blood flows into the left ventricle and is pumped through the arteries to the tissues. The major openings in the walls of the right atrium are (1) the points of entrance for the superior and inferior venae cavae (the great veins that return blood from the bodily tissues), and for the coronary sinus, the dilated terminal part of the cardiac vein, bearing venous blood from the heart muscle itself; and (2) the opening into the right ventricle. The principal openings into the left atrium are the points of entry of the pulmonary veins, bringing oxygenated blood from the lungs, and the opening into the left ventricle. See also ventricle.
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