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Those abdominal and thoracic structures that contribute to the expansion and contraction of the lungs. Movement of the chest and abdomen alters central pressures during inspiration and expiration. During inspiration, decreases in intrathoracic pressure draw air into the trachea, bronchi, and lungs and draw blood into the vena cava and right atrium of the heart. During expiration, intrathoracic pressures rise, and air is forced out of the lungs.
See also: pump