MCAT Biology : Fetal Circulation

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #52 : Biology

What fetal organs is blood shunted away from during gestation?

Possible Answers:

The kidneys and spleen

The lungs and liver

The lungs and intestines

The lungs and kidneys

The liver and spleen

Correct answer:

The lungs and liver

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.

Example Question #78 : Mcat Biological Sciences

The ductus arteriosus functions as a blood shunt during fetal development. Which circulatory components does the ductus arteriosus connect?

Possible Answers:

It shunts blood from the pulmonary artery to the aorta

It shunts blood from the right atrium to the left atrium

It shunts blood from the aorta to the pulmonary artery

It shunts blood away from the fetal liver

It shunts blood from the left atrium to the right atrium

Correct answer:

It shunts blood from the pulmonary artery to the aorta

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.

Example Question #77 : Mcat Biological Sciences

What is erythroblastosis fetalis?

Possible Answers:

A fatal condition in which the zygote implants in an area other than the uterine lining

A dangerous syndrome that can result from mother/baby Rh factor incompatibility

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

The process by which fetal erythrocytes grow and mature

Correct answer:

A dangerous syndrome that can result from mother/baby Rh factor incompatibility

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. 

Example Question #1 : Fetal Circulation

During what stage of pregnancy does a fetus's heart begin to beat?

Possible Answers:

Second trimester

Third trimester

First trimester

The fetus's heart does not begin to beat until after delivery.

Fourth trimester

Correct answer:

First trimester

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.

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