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 A
Explanation
Choice A rationale
The uterus can indeed increase in size by 20 times its non-pregnant size. This significant expansion is necessary to accommodate the growing fetus and the increased blood supply required during pregnancy.
Choice B rationale
While the weight of the uterus does increase significantly during pregnancy, from about 100 grams to approximately 1,000 grams, this statement does not directly address the client’s concern about the uterus’s ability to stretch.
Choice C rationale
About 25% of the increased capacity of the uterus is related to uteroplacental content, but this does not fully explain the uterus’s ability to stretch to accommodate a full-term baby.
Choice D rationale
The increase in uterus size during pregnancy is not solely related to amniotic fluid volume. The uterus itself grows and stretches significantly to accommodate the developing fetus.
Correct Answer is D
Explanation
Choice A rationale
A 25%-35% increase in blood volume is lower than the actual increase observed during pregnancy. This choice is incorrect.
Choice B rationale
A 10%-20% increase in blood volume is significantly lower than the actual increase observed during pregnancy. This choice is incorrect.
Choice C rationale
A 60%-70% increase in blood volume is higher than the actual increase observed during pregnancy. This choice is incorrect.
Choice D rationale
The correct percentage of increased blood volume during pregnancy is 40%-50%. This increase helps accommodate the growing fetus and placenta, and prepares the body for the blood loss that occurs during delivery.