As relates to the structure and function of the placenta, the ...

[gonzo233]

As relates to the structure and function of the placenta, the maternity nurse should be aware that:
 
  a. As the placenta widens, it gradually thins to allow easier passage of air and nutrients.
  b. As one of its early functions, the placenta acts as an endocrine gland.
  c. The placenta is able to keep out most potentially toxic substances such as cigarette smoke to which the mother is exposed.
  d. Optimal blood circulation is achieved through the placenta when the woman is lying on her back or standing.

Question 2

With regard to the development of the respiratory system, maternity nurses should be understand that:
 
  a. The respiratory system does not begin developing until after the embryonic stage.
  b. The infant's lungs are considered mature when the lecithin/sphingomyelin (L/S) ratio is 1:1, at about 32 weeks.
  c. Maternal hypertension can reduce maternal-placental blood flow, accelerating lung maturity.
  d. Fetal respiratory movements are not visible on ultrasound scans until at least 16 weeks.

[strudel15]

Answer to Question 1

ANS: B
The placenta produces four hormones necessary to maintain the pregnancy. The placenta widens until week 20 and continues to grow thicker. Toxic substances such as nicotine and carbon monoxide readily cross the placenta into the fetus. Optimal circulation occurs when the woman is lying on her side.

Answer to Question 2

ANS: C
A reduction in placental blood flow stresses the fetus, increases blood levels of corticosteroids, and accelerates lung maturity. Development of the respiratory system begins during the embryonic phase and continues into childhood. The infant's lungs are mature when the L/S ratio is 2:1, at about 35 weeks. Lung movements have been seen on ultrasound scans at 11 weeks.