Maternity Nursing: Antepartum Q 11
A nurse is describing the process of fetal circulation to a client during a prenatal visit. The nurse accurately tells the client that fetal circulation consists of:
A. Two umbilical veins and one umbilical artery.
B. Two umbilical arteries and one umbilical vein.
C. Arteries carrying oxygenated blood to the fetus.
D. Veins carrying deoxygenated blood to the fetus.
Correct Answer: B. Two umbilical arteries and one umbilical vein.
Blood pumped by the embryo’s heart leaves the embryo through two umbilical arteries. Once oxygenated, the blood then is returned by one umbilical vein. Arteries carry deoxygenated blood and waste products from the fetus, and veins carry oxygenated blood and provide oxygen and nutrients to the fetus.
Option A: The fetal circulation system is distinctly different from adult circulation. This intricate system allows the fetus to receive oxygenated blood and nutrients from the placenta. It comprises the blood vessels in the placenta and the umbilical cord, which contains two umbilical arteries and one umbilical vein.
Option C: Oxygenated blood from the mother in the placenta flows through the umbilical vein and into the inferior vena cava (IVC), bypassing the liver via the ductus venosus. From the IVC, oxygenated blood travels to the right atrium of the heart. There is greater pressure in the right atrium compared to the left atrium in fetal circulation; therefore most of the blood is shunted from the right atrium to the left atrium through an opening called the foramen ovale. Once in the left atrium, blood travels through the left ventricle into the aorta and the systemic circulation.
Option D: The deoxygenated blood travels back to the placenta via the umbilical arteries to be oxygenated by the mother. Additionally, some oxygenated blood in the right atrium can also enter the right ventricle and then the pulmonary artery. Because there is high resistance to blood flow in the lungs, the blood is shunted from the pulmonary artery into the aorta via the ductus arteriosus, hence bypassing the lungs. Blood then enters the systemic circulation, and the deoxygenated blood is recycled back to the mother via the umbilical arteries.