Oxygenated blood from placenta returns to the foetus via the \ \ \ \ \ \ ? - AIIMS Patna NO - 2020

AIIMS Patna NO - 2020

Obstetrics & Gynaecology

Easy

Appeared in: AIIMS Patna NO - 2020

Explanation

In fetal life, the lungs do not perform gas exchange; this function is carried out by the placenta.
The umbilical vein is the sole vessel that transports highly oxygenated and nutrient-rich blood from the placenta to the fetus.
Upon entering the fetus, much of this oxygenated blood is shunted past the liver by the ductus venosus to enter the inferior vena cava and supply the heart and brain.
The other vessels listed either carry deoxygenated blood or are shunts that divert blood away from the non-functional fetal lungs.

Option A: The superior vena cava carries deoxygenated blood returning from the upper body (head and arms) of the fetus to the right atrium.
Option B: The inferior vena cava (IVC) carries a mixture of blood. It receives deoxygenated blood from the lower body and oxygenated blood from the umbilical vein via the ductus venosus. Therefore, it is not the primary vessel returning fully oxygenated blood from the placenta.
Option D: The ductus arteriosus is a vascular shunt that connects the pulmonary artery to the aorta, allowing blood to bypass the fetal lungs. It carries mixed, less-oxygenated blood from the right ventricle.

Clinical Relevance

Nursing practice connection: Knowing Fetal circulation and the pathway of oxygenated blood from the placenta helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding fetal circulation is fundamental for neonatal resuscitation and assessing the newborn's transition to extrauterine life.
At birth, the clamping of the umbilical cord stops blood flow from the placenta, and the baby's first breath initiates the closure of fetal shunts (ductus arteriosus, foramen ovale, ductus venosus), transitioning to adult circulation.
Delayed cord clamping allows more blood to transfer from the placenta to the newborn, which can improve iron stores, but it must be balanced against risks like jaundice.

How to Approach the Question

First, identify the core concept of the question, which is the pathway of oxygenated blood in the fetus.
Recall the major structures of fetal circulation: the placenta, umbilical cord (vein and arteries), and the three fetal shunts (ductus venosus, foramen ovale, ductus arteriosus).
Remember the function of the placenta is to act as the 'lungs' for the fetus, providing oxygen.
Trace the path of blood leaving the placenta. Oxygenated blood must travel to the fetus. The umbilical vein is the vessel that does this.
Evaluate the other options: The vena cavae are major veins returning blood to the heart from the body, and the ductus arteriosus is a shunt within the fetal circulatory system to bypass the lungs. This process of elimination confirms the umbilical vein is the correct answer.

Concept Tested & Keywords

Concept Tested: Fetal circulation and the pathway of oxygenated blood from the placenta.
Stem keywords: Oxygenated blood, placenta, foetus
Lead-in keywords: returns to

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