What is the function of the ductus arteriosus?

The ductus arteriosus serves a critical role in fetal circulation by allowing blood to bypass the pulmonary circulation. During fetal development, the lungs are not yet functional for gas exchange, as the fetus receives oxygenated blood through the placenta. The ductus arteriosus connects the pulmonary artery to the aorta, which enables oxygen-poor blood from the right ventricle to flow directly into the aorta, effectively bypassing the non-functioning lungs. This adaptation ensures that blood can circulate throughout the body without needing to pass through the lungs, thus preserving the limited blood flow to that area during gestation. Following birth, when the lungs become functional and the circulatory system shifts to accommodate breathing air, the ductus arteriosus typically closes, preventing blood from bypassing the lungs in the postnatal period.