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Q1
Which blood vessel in the fetal pig transports oxygen-rich blood
from the placenta to the fetus before birth?
A. Umbilical artery
B. Umbilical vein
C. Pulmonary artery
D. Ductus arteriosus
Correct Answer: B
Verified Explanation
In fetal circulation, the umbilical vein is unique because it carries oxygenated
blood, which is the opposite of how veins function after birth. The placenta, not
the lungs, performs gas exchange for the fetus. Oxygenated blood leaves the
placenta and enters the fetus through the umbilical vein. This blood then travels
toward the liver, where much of it bypasses hepatic circulation via the ductus
venosus and enters the inferior vena cava. This design ensures that the most
oxygen-rich blood is delivered quickly to critical organs such as the heart and
brain. Marieb’s fetal pig manual highlights the umbilical vein as the primary
lifeline between mother and fetus.
Q2
Which fetal structure allows blood to pass directly
from the right atrium to the left atrium?
A. Ductus venosus
B. Ductus arteriosus
C. Foramen ovale
D. Interventricular septum
Correct Answer: C
Verified Explanation
The foramen ovale is an opening in the interatrial septum of the fetal heart that
allows blood to bypass the lungs. Since the fetal lungs are nonfunctional and
filled with fluid, pulmonary resistance is very high. If blood were forced
through the lungs, circulation would be inefficient and oxygen delivery would
decrease. The foramen ovale ensures that oxygenated blood entering the right
atrium flows directly into the left atrium, where it is pumped into systemic
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circulation. After birth, increased pulmonary blood flow raises left atrial
pressure, forcing the foramen ovale to close and form the fossa ovalis.
Q3
Which fetal vessel shunts blood away from the liver
by connecting the umbilical vein to the inferior vena cava?
A. Umbilical artery
B. Foramen ovale
C. Ductus arteriosus
D. Ductus venosus
Correct Answer: D
Verified Explanation
The ductus venosus is responsible for diverting oxygenated blood away from
the fetal liver. While the liver is essential after birth, the fetus prioritizes rapid
oxygen delivery to the heart and brain. The ductus venosus connects the
umbilical vein directly to the inferior vena cava, bypassing hepatic circulation.
This efficient shortcut ensures that high-quality blood reaches systemic
circulation quickly. After birth, when placental circulation ends, the ductus
venosus closes and becomes the ligamentum venosum. In fetal pig dissections,
this vessel is visible running between the liver and vena cava.
Q4
Which structure carries blood from the pulmonary artery
directly into the aorta during fetal life?
A. Foramen ovale
B. Ductus arteriosus
C. Umbilical vein
D. Ductus venosus
Correct Answer: B
Verified Explanation
The ductus arteriosus connects the pulmonary trunk to the aorta, allowing
blood to bypass the nonfunctional fetal lungs. Because fetal lungs are collapsed,
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pulmonary circulation has very high resistance. The ductus arteriosus ensures
that blood pumped from the right ventricle does not waste energy attempting to
pass through the lungs but instead flows directly into the systemic circulation.
After birth, as oxygen levels increase and pulmonary resistance drops, the
ductus arteriosus constricts and eventually becomes the ligamentum arteriosum
in the adult heart.
Q5
Which fetal vessel carries carbon-dioxide-rich blood
from the fetus back to the placenta?
A. Umbilical vein
B. Pulmonary artery
C. Umbilical artery
D. Ductus venosus
Correct Answer: C
Verified Explanation
The umbilical arteries carry deoxygenated blood from the fetus to the placenta.
This blood is rich in carbon dioxide and metabolic wastes. Unlike adult arteries,
which carry oxygenated blood, fetal umbilical arteries perform the opposite
function because the placenta, not the lungs, removes waste. The umbilical
arteries branch from the internal iliac arteries and travel through the umbilical
cord to the placenta. There, gas exchange occurs, and carbon dioxide is
removed from the fetal blood. This reversed circulation is a defining feature of
fetal physiology described in Marieb’s fetal pig manual.
Q6
Which fetal structure later forms the ligamentum arteriosum
after it closes at birth?
A. Foramen ovale
B. Umbilical vein
C. Ductus arteriosus
D. Ductus venosus
Correct Answer: C
Verified Explanation
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Q1
Which blood vessel in the fetal pig transports oxygen-rich blood
from the placenta to the fetus before birth?
A. Umbilical artery
B. Umbilical vein
C. Pulmonary artery
D. Ductus arteriosus
Correct Answer: B
Verified Explanation
In fetal circulation, the umbilical vein is unique because it carries oxygenated
blood, which is the opposite of how veins function after birth. The placenta, not
the lungs, performs gas exchange for the fetus. Oxygenated blood leaves the
placenta and enters the fetus through the umbilical vein. This blood then travels
toward the liver, where much of it bypasses hepatic circulation via the ductus
venosus and enters the inferior vena cava. This design ensures that the most
oxygen-rich blood is delivered quickly to critical organs such as the heart and
brain. Marieb’s fetal pig manual highlights the umbilical vein as the primary
lifeline between mother and fetus.
Q2
Which fetal structure allows blood to pass directly
from the right atrium to the left atrium?
A. Ductus venosus
B. Ductus arteriosus
C. Foramen ovale
D. Interventricular septum
Correct Answer: C
Verified Explanation
The foramen ovale is an opening in the interatrial septum of the fetal heart that
allows blood to bypass the lungs. Since the fetal lungs are nonfunctional and
filled with fluid, pulmonary resistance is very high. If blood were forced
through the lungs, circulation would be inefficient and oxygen delivery would
decrease. The foramen ovale ensures that oxygenated blood entering the right
atrium flows directly into the left atrium, where it is pumped into systemic
,3|Page
circulation. After birth, increased pulmonary blood flow raises left atrial
pressure, forcing the foramen ovale to close and form the fossa ovalis.
Q3
Which fetal vessel shunts blood away from the liver
by connecting the umbilical vein to the inferior vena cava?
A. Umbilical artery
B. Foramen ovale
C. Ductus arteriosus
D. Ductus venosus
Correct Answer: D
Verified Explanation
The ductus venosus is responsible for diverting oxygenated blood away from
the fetal liver. While the liver is essential after birth, the fetus prioritizes rapid
oxygen delivery to the heart and brain. The ductus venosus connects the
umbilical vein directly to the inferior vena cava, bypassing hepatic circulation.
This efficient shortcut ensures that high-quality blood reaches systemic
circulation quickly. After birth, when placental circulation ends, the ductus
venosus closes and becomes the ligamentum venosum. In fetal pig dissections,
this vessel is visible running between the liver and vena cava.
Q4
Which structure carries blood from the pulmonary artery
directly into the aorta during fetal life?
A. Foramen ovale
B. Ductus arteriosus
C. Umbilical vein
D. Ductus venosus
Correct Answer: B
Verified Explanation
The ductus arteriosus connects the pulmonary trunk to the aorta, allowing
blood to bypass the nonfunctional fetal lungs. Because fetal lungs are collapsed,
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pulmonary circulation has very high resistance. The ductus arteriosus ensures
that blood pumped from the right ventricle does not waste energy attempting to
pass through the lungs but instead flows directly into the systemic circulation.
After birth, as oxygen levels increase and pulmonary resistance drops, the
ductus arteriosus constricts and eventually becomes the ligamentum arteriosum
in the adult heart.
Q5
Which fetal vessel carries carbon-dioxide-rich blood
from the fetus back to the placenta?
A. Umbilical vein
B. Pulmonary artery
C. Umbilical artery
D. Ductus venosus
Correct Answer: C
Verified Explanation
The umbilical arteries carry deoxygenated blood from the fetus to the placenta.
This blood is rich in carbon dioxide and metabolic wastes. Unlike adult arteries,
which carry oxygenated blood, fetal umbilical arteries perform the opposite
function because the placenta, not the lungs, removes waste. The umbilical
arteries branch from the internal iliac arteries and travel through the umbilical
cord to the placenta. There, gas exchange occurs, and carbon dioxide is
removed from the fetal blood. This reversed circulation is a defining feature of
fetal physiology described in Marieb’s fetal pig manual.
Q6
Which fetal structure later forms the ligamentum arteriosum
after it closes at birth?
A. Foramen ovale
B. Umbilical vein
C. Ductus arteriosus
D. Ductus venosus
Correct Answer: C
Verified Explanation
