A nurse is discussing fetal circulation with a group of nursing students.The ductus venosus, foramen ovale, and ductus arteriosus are key factors in fetal circulation.Which of the following explains the purpose of these shunts in fetal circulation?
To bypass the lungs and direct oxygenated blood to the brain and body.
To ensure proper development of the fetal heart.
To regulate blood pressure in the fetus.
To facilitate gas exchange in the lungs.
The Correct Answer is A
Choice A rationale
The ductus venosus, foramen ovale, and ductus arteriosus are shunts in fetal circulation that bypass the lungs and liver, directing oxygenated blood to the brain and body. The foramen ovale allows blood to flow from the right atrium to the left atrium, bypassing the lungs. The ductus arteriosus connects the pulmonary artery to the aorta, allowing blood to bypass the lungs. The ductus venosus shunts blood from the umbilical vein to the inferior vena cava, bypassing the liver.
Choice B rationale
This choice is incorrect because the primary purpose of these shunts is not to ensure proper development of the fetal heart. While they do play a role in directing blood flow, their main function is to bypass the non-functional fetal lungs and liver.
Choice C rationale
This choice is incorrect because the shunts are not primarily involved in regulating blood pressure in the fetus. Their main function is to direct oxygenated blood to vital organs like the brain and heart.
Choice D rationale
This choice is incorrect because the shunts bypass the lungs, which are not yet functional in the fetus. Gas exchange occurs in the placenta, not the fetal lungs.
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Correct Answer is C
Explanation
Choice A rationale
The placenta does not cushion the fetus from maternal movement. Instead, the amniotic fluid within the amniotic sac provides cushioning and protection to the fetus from external forces and maternal movements.
Choice B rationale
The placenta does not provide thermoregulation. Thermoregulation is primarily managed by the mother’s body. The placenta’s main functions are related to nutrient and gas exchange, hormone production, and waste removal.
Choice C rationale
The placenta is responsible for metabolic and gas exchange. It provides oxygen and nutrients to the fetus while removing waste products from the fetal blood. This exchange occurs through the placental barrier, which separates maternal and fetal blood.
Choice D rationale
The placenta does not provide a sterile environment. The amniotic sac and its fluid help maintain a sterile environment for the fetus. The placenta’s role is more focused on nutrient and gas exchange, hormone production, and waste removal.
Correct Answer is B
Explanation
Choice A rationale
Oligohydramnios refers to a condition where there is too little amniotic fluid. An amniotic fluid volume of 1900 mL is above the normal range, indicating that oligohydramnios is not present.
Choice B rationale
Polyhydramnios is the condition of having too much amniotic fluid. The normal range for amniotic fluid volume at 34 weeks gestation is between 800 and 1000 mL. An estimated volume of 1900 mL indicates polyhydramnios, which can be associated with various maternal and fetal conditions.
Choice C rationale
A follow-up glucose test is not directly indicated by the finding of polyhydramnios. While polyhydramnios can be associated with gestational diabetes, the decision to perform a glucose test would depend on other clinical factors and the patient’s history.
Choice D rationale
An amniotic fluid volume of 1900 mL is above the normal range for 34 weeks gestation, so it is not considered normal for gestational age. This finding indicates polyhydramnios rather than a normal fluid level.