A nurse is teaching a newly pregnant patient about how oxygen and nutrients reach her developing baby.
Which of the following responses by the patient indicates a need for further teaching?
"I share oxygen and nutrients with my baby through a process called diffusion. Our blood does not come into contact, but it is close enough that these materials can easily pass from me to the baby.”.
"I am able to give my baby the oxygen I breathe and the nutrients from the food that I eat. These substances are in my blood and travel to an area that acts as a border between my blood and the baby's blood. The oxygen and nutrients can easily travel through this border, which is called the chorionic villi.”.
"The baby and I do not share blood. I supply the baby with nutrients and the baby gets rid of wastes and carbon dioxide by passing these materials back to me, but our blood does not mix.”.
"The baby and I share blood. Whatever oxygen I breathe in and whatever food that I eat gets to the baby through our shared blood in the placenta and umbilical cord.”.
The Correct Answer is D
Choice A rationale
This statement accurately describes the physiological process of nutrient and gas exchange in the placenta. Diffusion is the primary mechanism, driven by concentration gradients, where oxygen and nutrients move from the maternal blood into the fetal circulation, and waste products move from fetal to maternal blood. The placental barrier, though thin, ensures that maternal and fetal bloodstreams remain separate, preventing direct mixing. This separation is crucial for immunological compatibility.
Choice B rationale
This response demonstrates a correct understanding of placental anatomy and function. The chorionic villi are finger-like projections of the placenta that extend into the maternal decidua. They are rich in fetal capillaries and are the primary site of exchange between maternal and fetal blood. The close proximity allows for efficient transfer of essential substances like oxygen and nutrients, and removal of waste products.
Choice C rationale
This statement is physiologically accurate. The maternal and fetal circulatory systems are distinct; there is no direct mixing of blood. The placenta acts as an interface for exchange. The mother provides oxygen and nutrients, while the fetus returns metabolic waste products, including carbon dioxide and urea, to the maternal circulation for excretion. This maintains separate, yet interdependent, physiological systems.
Choice D rationale
This statement is incorrect and indicates a need for further teaching. The maternal and fetal bloodstreams do not directly mix. The placenta serves as a critical barrier and exchange organ, facilitating the transfer of substances via diffusion, active transport, and facilitated diffusion, but maintaining the separation of the two circulatory systems. Direct blood mixing would lead to severe immunological complications.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
Choice A rationale
Dark, cloudy urine is generally indicative of dehydration or a urinary tract infection, not an impending ovulation. Urine characteristics are primarily related to hydration status and renal function, not the hormonal fluctuations associated with the ovulatory cycle. Therefore, it is not a reliable indicator of fertility.
Choice B rationale
Breast tenderness is often a symptom associated with the luteal phase of the menstrual cycle, occurring after ovulation, due to rising progesterone levels. It is caused by hormonal influences on mammary gland tissue, but it does not reliably predict the immediate approach of ovulation.
Choice C rationale
Cervical mucus that becomes thin, clear, stretchy, and abundant, often described as "egg-white" consistency, is a reliable physiological indicator of impending ovulation. This change is induced by rising estrogen levels, which facilitate sperm transport through the cervix into the uterus, increasing fertility around the time of ovulation.
Choice D rationale
A consistently low basal body temperature (BBT) typically characterizes the follicular phase before ovulation. A sustained slight increase in BBT (0.5 to 1.0°F or 0.2 to 0.5°C) occurs after ovulation, driven by the thermogenic effect of progesterone. Therefore, a consistently low temperature indicates pre-ovulatory status, not imminent ovulation.
Correct Answer is C
Explanation
Choice A rationale
The placenta is a crucial endocrine organ that synthesizes and secretes several hormones vital for maintaining pregnancy. These include human chorionic gonadotropin (hCG), progesterone, estrogen, and human placental lactogen (hPL), also known as human chorionic somatomammotropin (hCS). These hormones collectively support the uterine environment, prevent maternal immune rejection, and promote fetal growth and development throughout gestation.
Choice B rationale
The placenta is indeed responsible for producing key hormones such as estrogen, primarily estriol, which promotes uterine growth and uteroplacental blood flow; progesterone, essential for maintaining the uterine lining and preventing contractions; human chorionic gonadotropin (hCG), which supports the corpus luteum; and human placental lactogen (hPL) or human chorionic somatomammotropin (hCS), which modulates maternal metabolism to provide nutrients for the fetus.
Choice C rationale
Placental development begins very early in pregnancy, around the second week post-fertilization, with the formation of the chorionic villi. By 8 weeks of gestation, the placenta is already well-established and actively performing its functions of hormone production and nutrient/waste exchange. Therefore, the statement that it has not yet begun to develop at 8 weeks indicates a significant misunderstanding of embryonic and fetal development timelines.
Choice D rationale
The placenta functions as the primary interface for maternal-fetal exchange. Its highly vascularized structure facilitates the efficient transfer of oxygen, glucose, amino acids, and other essential nutrients from the mother to the fetus. Concurrently, metabolic waste products, such as carbon dioxide and urea, are transported from the fetal circulation back to the maternal circulation for excretion, ensuring fetal homeostasis.
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