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The fetal heart contains two upper atria and two lower ventricles. It also contains two additional structures, the foramen ovale and the ductus arteriosus, that function as shunts for oxygenated blood. [2] The function of these shunts is to bypass the lungs and maintain proper circulation to
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Ductus arteriosus evolved with the lung in the ancestors of the lungfish as a connection between the pulmonary arteries and dorsal aorta. During embryonic development, reptiles, birds, and mammals all have either one or two paired ductus arteriosi that provide a fetal shunt of blood away from the lungs. [10]
In many cases, TGV is accompanied by other heart defects, the most common type being intracardiac shunts such as atrial septal defect including patent foramen ovale, ventricular septal defect, and patent ductus arteriosus. Stenosis, or other defects, of valves and/or vessels may also be present. [citation needed]
Patent ductus arteriosus (PDA) is a medical condition in which the ductus arteriosus fails to close after birth: this allows a portion of oxygenated blood from the left heart to flow back to the lungs from the aorta, which has a higher blood pressure, to the pulmonary artery, which has a lower blood pressure.
Following birth and separation from the placenta, the oxygen content in the inferior vena cava falls. With the onset of breathing, the left atrium receives oxygen-rich blood from the lungs via the pulmonary veins. As blood flow to the lungs increases, the amount of blood flow entering the left atrium increases.
In adults, the ligamentum arteriosum has no useful function. It is a vestige of the ductus arteriosus, a temporary fetal structure that shunts blood from the pulmonary arteries to the aorta. This significantly reduces the volume of blood circulating through the lungs, which are inactive in the womb.
A catheter may be inserted into one of the umbilical arteries of critically ill babies for drawing blood for testing. [6] This is a common procedure in neonatal intensive care, and can often be performed until 2 weeks after birth (when the arteries start to decay too much). [7]