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 B
Explanation
Choice A rationale
Fetal movements, known as quickening, are typically felt by the mother between 16 and 25 weeks of pregnancy, not specifically at week 245.
Choice B rationale
The baby’s heartbeat can be detected by 10-12 weeks of pregnancy using a Doppler ultrasound device. This is an important milestone in fetal development and prenatal care
.
Choice C rationale
Lanugo, the fine hair covering the fetus, usually appears around 20 weeks of pregnancy and starts to disappear closer to the end of the third trimester, not specifically by week 355.
Choice D rationale
The sex of the baby is determined at conception, but it can be detected via ultrasound around 18-20 weeks of pregnancy, not by week 85.
Correct Answer is B
Explanation
Choice A rationale
The mother’s size does not significantly impact the effects of teratogen exposure on fetal development. Teratogens are substances that cause congenital abnormalities in a developing fetus, and their impact is more related to the timing, duration, and type of exposure rather than the mother’s physical characteristics.
Choice B rationale
The timing and duration of exposure are critical factors in determining the effects of teratogen exposure. Teratogens can cause the most harm during specific periods of fetal development, particularly during the first trimester when organogenesis occurs. The duration of exposure also influences the severity of the effects, with prolonged exposure leading to more significant developmental issues.
Choice C rationale
The type of teratogen is also important, as different teratogens can cause different types of congenital abnormalities. For example, alcohol can lead to fetal alcohol syndrome, while certain medications can cause neural tube defects. However, the timing and duration of exposure are generally considered more critical factors.
Choice D rationale
The father’s health does not directly impact the effects of teratogen exposure on fetal development. Teratogens affect the fetus through the mother’s exposure to harmful substances during pregnancy.