Question at position 18 What is the function of the ductus arteriosus in fetal circulation?It closes immediately after birth to increase blood flow to the lungs.It transfers oxygenated blood from the placenta to the fetus.It diverts blood from the pulmonary trunk to the aorta.It allows blood to bypass the fetal liver.It connects the left atrium to the left ventricle.

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BlackTom AI · Accepted Answer

To begin, I will restate the question and all options to ensure clarity about what is being evaluated.
Question: What is the function of the ductus arteriosus in fetal circulation?
Options:
1) It closes immediately after birth to increase blood flow to the lungs.
2) It transfers oxygenated blood from the placenta to the fetus.
3) It diverts blood from the pulmonary trunk to the aorta.
4) It allows blood to bypass the fetal liver.
5) It connects the left atrium to the left ventricle.

Now, I will analyze each option individually.
Option 1: It closes immediately after birth to increase blood flow to the lungs. This statement mixes postnatal events with a prenatal structure. The ductus arteriosus indeed closes after birth, but its closing is a consequence of adapting to life outside the womb and is aimed at routing blood to the lungs after birth, not increasing blood flow to the lungs before birth. As a description of the fetal function, this is inaccurate.

Option 2: It transfers oxygenated blood from the placenta to the fetus. In fetal circulation, oxygenated blood reaches the fetus via the umbilical vein from the placenta; the ductus arteriosus is not the conduit for placental blood. Therefore, this option misstates the pathway and is incorrect.

Option 3: It diverts blood from the pulmonary trunk to the aorta. This matches the established role of the ductus arteriosus: during fetal life, it provides a shunt from the pulmonary artery (pulmonary trunk) to the aorta, bypassing the nonfunctional fetal lungs. This is a correct description of its function.

Option 4: It allows blood to bypass the fetal liver. Bypassing the liver is primarily associated with the ductus venosus, which shunts blood from the umbilical vein toward the inferior vena cava, bypassing the liver. The ductus arteriosus serves a different purpose, so this option is incorrect.

Option 5: It connects the left atrium to the left ventricle. The connection between the atria is the foramen ovale, and the connection between the right ventricle/pulmonary artery and the aorta is the ductus arteriosus. Therefore this option inaccurately describes a different fetal structure and is incorrect.

In summary, option 3 accurately describes the ductus arteriosus function in fetal circulation by diverting blood from the pulmonary trunk to the aorta, whereas the other options either describe postnatal changes, other fetal shunts, or incorrect anatomical connections.

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