|MadSci Network: Development|
Dear Allie, The advantage of having a ductus arteriosus and a foramen ovale is that the pulmonary circulation is bypassed. The pulmonary circulation is those vessels which go through the lungs, but the lungs do not work when a baby is still in the uterus, because there is no air. Instead the baby gets oxygen from its mother's blood through the umbilical cord. In an adult all the blood that gets pumped through the heart goes through the lungs to get oxygen, then to the rest of the body. The blood first goes to the right side of the heart, then the lungs, then the left side of the heart, then the body. In a baby the blood mostly goes through the right side of the heart, then through the foramen ovale to the left side of the heart, and then to the rest of the body, but of the blood that goes through the pulmonary circulation, most of it never actually reaches the lungs, but instead goes through the ductus arteriosus then to the aorta, where it goes to the rest of the body. So you see, the foramen ovale and the ductus arteriosus both help a baby's blood bypass the lungs. Shortly after birth the ductus arteriosus and the foramen ovale both close, since now the baby must have all its blood oxygenated in the lungs. Thank you for your question. Sincerely, Sarah Martin Mason, Mad Scientist
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