RT Book, Section A1 Naeije, R. A2 Grippi, Michael A. A2 Elias, Jack A. A2 Fishman, Jay A. A2 Kotloff, Robert M. A2 Pack, Allan I. A2 Senior, Robert M. A2 Siegel, Mark D. SR Print(0) ID 1122355141 T1 Pulmonary Circulation T2 Fishman's Pulmonary Diseases and Disorders, 5e YR 2015 FD 2015 PB McGraw-Hill Education PP New York, NY SN 978-0-07-179672-9 LK accessmedicine.mhmedical.com/content.aspx?aid=1122355141 RD 2024/03/29 AB The discovery of the pulmonary circulation was reported in the 13th century by Ibn al-Nafis (1213–1288) in the “Commentary on Anatomy in Avicenna's Canon” and, probably independently, in the 16th century by Michael Servetus (1511–1553) in the “The Restoration of Christianity.”1 However, it has only been recently realized that the pulmonary circulation as a separate high-flow low-pressure system is the end result of an evolutionary process aimed at the optimization of gas exchange of endothermic birds and mammals.2 Evolution from ancestors of fishes to amphibians, reptiles, and finally birds and mammals has led to progressively greater oxygen consumption requiring thinner pulmonary blood–gas barrier. The alveolocapillary membrane in mammals is a vulnerable structure only 0.3 μm thick. Preservation of the integrity of this barrier has been made possible by the complete separation of the pulmonary circulation from the systemic circulation. This evolution has been accompanied by a progressive unloading and reshaping of the right ventricle (RV) as a thin-walled flow generator.