The yolk sac __________.

Correct Answer: C

Rationale: The yolk sac is an extraembryonic membrane that plays a significant role in the early development of the embryo. One of its functions is to produce blood cells until the organs are mature enough to take over this function. This process occurs during the early stages of prenatal development to support the growing embryo before it can sustain itself independently.

Correct Answer: A

Rationale: In pharmacology, understanding fetal development is crucial for assessing drug safety during pregnancy. During the twelfth week of pregnancy, the correct answer is A) the sex of the fetus can be detected with ultrasound. This is because by this time, the genitalia have developed sufficiently to be visualized on an ultrasound scan, allowing for the determination of the fetus's sex. Option B) stating that the mother can feel the movements of the fetus is incorrect for the twelfth week as fetal movements, known as quickening, are typically felt between 16-25 weeks of pregnancy. Option C) claiming the fetus is viable and can survive if born early is inaccurate at 12 weeks as fetal viability, generally considered around 24 weeks, depends on various factors including lung development and weight. Option D) mentioning synchrony between fetal heart rate and motor activity peaks is not relevant at the twelfth week of pregnancy as fetal movements and cardiac activity do not yet exhibit such coordinated patterns. Educationally, knowing the timeline of fetal development is essential in pharmacology to understand how drugs may impact the developing fetus at different stages of pregnancy. Ultrasound plays a vital role in monitoring fetal growth and development, allowing healthcare providers to assess the health of the fetus and detect any potential abnormalities early on.

Correct Answer: A

Rationale: In pharmacology, understanding fetal development is crucial as it impacts drug effects on both mother and fetus. In this scenario, the correct answer is A) a 20-week-old fetus can be stimulated as well as irritated by sounds. At this stage, the fetus's auditory system is developing, allowing it to perceive sounds. This is supported by research showing fetal responses to external stimuli like music or voices. Option B) is incorrect because fetal viability outside the womb typically begins around 24 weeks, so a 20-week-old fetus would not survive if born prematurely. Option C) is incorrect as premature infants often require oxygen support to breathe due to underdeveloped lungs. Option D) is incorrect as fetal thermoregulation is not fully developed at 20 weeks, so the fetus cannot control its body temperature. Educationally, this question highlights the importance of understanding fetal development milestones for healthcare providers prescribing medications to pregnant women. It underscores the need to consider the impact of external stimuli on fetal well-being and the limitations of fetal viability and physiological functions at different gestational ages.

Correct Answer: D

Rationale: High doses of caffeine contained in coffee and tea have been linked to an increased risk of low birth weight. Consuming large amounts of caffeine during pregnancy can interfere with the baby's growth and development, leading to a lower birth weight than expected. It is important for pregnant women to limit their caffeine intake to reduce the risk of complications such as low birth weight.

Correct Answer: B

Rationale: Newborns of smoking mothers display more muscle tension. This is because nicotine in cigarettes can lead to increased muscle tension in babies, which can affect their physical development and potentially lead to future health issues. This is one of the negative effects of smoking during pregnancy on the developing fetus.