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Example Question #1 : Help With Fetal Circulation
Which structure is responsible for bypassing the fetal liver and taking blood directly to the right atrium?
Because the fetal lungs and liver are not fully functional until birth, the fetal circulation uses structures in order to bypass these organs.
The ductus venosus is used to reroute blood from the fetal liver and deposit it into the right atrium.
The ductus arteriosus connects the fetal pulmonary arteries to the aorta to bypass the lungs, while the foramen ovale connects the right and left atria to reduce flow to the pulmonary arteries.
The umbilical vein carries blood from the uterus, where it have been loaded with oxygen from maternal circulation, back to the body.
Example Question #2 : Help With Fetal Circulation
A fetal circulatory structure is used in order to take blood from the pulmonary trunk and reroute it to the fetal aorta. What does this structure become after birth?
The ductus arteriosus is used to reroute blood from the pulmonary trunk and place it into the aorta of the fetus, preventing flow to the non-functional fetal lungs. After birth, this structure deteriorates and closes. The ligamentum arteriosum is the vestigial structure that is seen in adults. Instead of connecting the pulmonary arteries and aorta, it helps to stabilize these structures.
The foramen ovale is a fetal window between the right and left atria to help blood bypass the pulmonary circuit. After birth, this window closes to become the fossa ovalis.