Fetal Circulation
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MCAT Biological and Biochemical Foundations of Living Systems › Fetal Circulation
What is erythroblastosis fetalis?
A dangerous syndrome that can result from mother/baby Rh factor incompatibility
The process by which fetal erythrocytes grow and mature
A fatal condition in which the zygote implants in an area other than the uterine lining
A syndrome in which the mother's hormones fail to engage, resulting in loss of pregnancy
A severe estrogen deficiency, resulting in partially developed reproductive organs
Explanation
Erythroblastosis fetalis is a rare conditon in which the mother's anti-Rh antibodies enter the fetal bloodstream and attach to fetal erythrocytes. If not caught, it can result in "blue-baby syndrome." Erythroblastosis is only present in patients negative for the Rh factor, and carrying Rh positive fetuses.
During what stage of pregnancy does a fetus's heart begin to beat?
First trimester
Second trimester
Third trimester
Fourth trimester
The fetus's heart does not begin to beat until after delivery.
Explanation
A pregnancy consists of three trimesters, each of which is approximately 12 weeks. The fetus's heart, brain, spinal cord, and other organs begin to form in approximately the fifth week of pregnancy—in the first trimester.
What fetal organs is blood shunted away from during gestation?
The lungs and liver
The lungs and intestines
The liver and spleen
The lungs and kidneys
The kidneys and spleen
Explanation
Oxygen diffuses from maternal blood to fetal blood through the placenta. Within the womb, the lungs are not able to work properly and so blood is rerouted through the foramen ovale and the ductus arteriosus. The liver is also underdeveloped, and not ready to perform the functions it will do in adulthood. The placenta takes over for the liver during gestation, and so blood is shunted away from the liver by the ductus venosus. This prevents oxygen that could be useful in other places from being wasted in the liver.
The ductus arteriosus functions as a blood shunt during fetal development. Which circulatory components does the ductus arteriosus connect?
It shunts blood from the pulmonary artery to the aorta
It shunts blood from the aorta to the pulmonary artery
It shunts blood from the right atrium to the left atrium
It shunts blood from the left atrium to the right atrium
It shunts blood away from the fetal liver
Explanation
The ductus arteriosus shunts blood from the pulmonary artery to the aorta in order to bypass the lungs, since the fetal lungs are not active.
The foramen ovale shunts blood from the right atrium to the left atrium, serving as another method to bypass the lungs. The ductus venosus shunts blood away from the fetal liver. There is no shunt from the aorta to the pulmonary artery, and there is no shunt from the left atrium to the right atrium.