AJR:200, April 2013

Stefan F. Nemec, Alexander A. Bankier, Ronald L. Eisenberg

The lung is a heterogeneous organ because of regional differences in perfusion- ventilation ratios and in lymphatic, metabolic, and mechanical properties, which are primarily influenced by gravity. In the erect individual, these differences result in relative overventilation of the lung apices and overperfusion of the lung bases. The relative apical overventilation and decreased apical lymphatic flow cause certain pulmonary diseases to have an upper lung predominance. The combination of gravity and relative overperfusion of the lung bases leads other disorders to predominantly involve the lower lung