RT Book, Section A1 Evans, Nick A2 Rudolph, Colin D. A2 Rudolph, Abraham M. A2 Lister, George E. A2 First, Lewis R. A2 Gershon, Anne A. SR Print(0) ID 6735976 T1 Chapter 56. Hemodynamics T2 Rudolph's Pediatrics, 22e YR 2011 FD 2011 PB The McGraw-Hill Companies PP New York, NY SN 978-0-07-149723-7 LK accesspediatrics.mhmedical.com/content.aspx?aid=6735976 RD 2024/03/29 AB An understanding of neonatal circulatory pathology is intrinsically linked to an understanding of circulatory adaptation to extrauterine life (see Chapter 43). In the fetal circulation, better oxygenated blood is returned from the placenta to the fetus via the umbilical vein. This blood is streamed by the ductus venosus across the right atrium, through the foramen ovale, and into the left atrium, facilitating delivery of the best oxygenated fetal blood to the brain and upper body. Blood returning via the vena cavae is streamed through the right side of the heart and into the descending aorta via the ductus arteriosus. This blood preferentially streams through the ductus because of arteriolar constriction and the high vascular resistance in the fetal lungs. The right-to-left ductal blood flow supplies the lower part of the body and also returns blood to the placenta via the umbilical arteries, which arise from the iliac arteries.