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Ch. 18 The Cardiovascular System: The Heart
Hoehn - Marieb Human Anatomy & Physiology, 12th edition
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Non è quello che usi tu?Cambia libro di testo
Capitolo 18, Problema 21

(a) Describe the common function of the foramen ovale and the ductus arteriosus in a fetus.
(b) What problems result if these shunts remain patent (open) after birth?

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(a) Begin by understanding the fetal circulation system, which includes special structures like the foramen ovale and the ductus arteriosus that allow blood to bypass the lungs, which are not yet functional before birth.
Explain that the foramen ovale is an opening between the right and left atria of the fetal heart, allowing blood to flow directly from the right atrium to the left atrium, bypassing the non-functioning fetal lungs.
Describe the ductus arteriosus as a vessel connecting the pulmonary artery to the aorta, which also helps divert blood away from the lungs by allowing it to flow directly into systemic circulation.
(b) Discuss the consequences if these shunts remain open (patent) after birth, when the lungs are supposed to take over oxygen exchange. This can cause abnormal blood flow patterns, leading to inefficient oxygenation and increased workload on the heart.
Specifically, explain that a patent foramen ovale or ductus arteriosus can cause mixing of oxygenated and deoxygenated blood, potentially resulting in symptoms such as cyanosis, heart murmur, or heart failure, depending on the severity.

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Fetal Circulatory Shunts

The foramen ovale and ductus arteriosus are fetal shunts that direct blood flow to bypass the non-functioning fetal lungs. The foramen ovale allows blood to flow from the right atrium to the left atrium, while the ductus arteriosus connects the pulmonary artery to the aorta, ensuring oxygenated blood reaches systemic circulation.
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Closure of Fetal Shunts After Birth

After birth, the lungs expand and begin oxygen exchange, causing the foramen ovale and ductus arteriosus to close. This closure redirects blood flow through the lungs for oxygenation. Proper closure is essential for normal postnatal circulation and oxygen delivery.
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The Placenta

Consequences of Patent Foramen Ovale and Ductus Arteriosus

If the foramen ovale or ductus arteriosus remain open (patent) after birth, abnormal blood flow occurs, leading to mixing of oxygenated and deoxygenated blood. This can cause complications such as hypoxemia, heart strain, and increased risk of infections or heart failure, requiring medical intervention.
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Nerves and Blood Supply
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