What is the primary function of the ductus arteriosus during fetal development?

The primary function of the ductus arteriosus during fetal development is to divert blood from the lungs. In the fetal circulation, the lungs are not yet fully developed, and thus, there is no need for blood to flow through the pulmonary circuit for oxygenation. Instead, the ductus arteriosus, which is a blood vessel connecting the pulmonary artery to the aorta, allows most of the blood from the right ventricle to bypass the non-functioning lungs and flow directly into the systemic circulation via the aorta. This adaptation is crucial for fetal survival as it ensures that oxygenated blood, received from the placenta, is delivered efficiently to the rest of the body while minimizing the volume of blood that goes to the lungs.

The other options describe processes that do not accurately represent the role of the ductus arteriosus. Filtering toxins, oxygenating blood, and supplying nutrients are functions associated with different structures and processes in fetal development, such as the placenta, rather than the ductus arteriosus itself. The ductus arteriosus specifically serves to optimize blood flow during a time when the fetus is dependent on placental oxygenation rather than pulmonary gas exchange.