Oxygenated blood enter the fetal circulation from umbilical vein via?

IGNOU PB Bsc Entrance-2023

Obstetrics & Gynaecology

Easy

Appeared in: IGNOU PB Bsc Entrance-2023

Explanation

In the fetus, oxygenated blood from the placenta travels through the umbilical vein.
The ductus venosus is a crucial shunt that connects the umbilical vein directly to the inferior vena cava.
This mechanism allows a significant portion of the highly oxygenated blood to bypass the fetal liver's circulation.
Bypassing the liver ensures that the most oxygen-rich blood is delivered efficiently to the fetal heart and brain, which have high oxygen demands.

Option B: The ductus arteriosus is a different fetal shunt. It connects the pulmonary artery to the aorta, allowing blood to bypass the non-functioning fetal lungs, not the liver.
Option C: While a portion of the umbilical vein's blood does enter the liver's sinusoids to supply the hepatic tissue (via intrahepatic veins), this is not the primary pathway for oxygenated blood to enter the main systemic circulation. The main shunt is the ductus venosus.
Option D: The intrahepatic artery is part of the arterial supply to the liver tissue, carrying blood from the fetal aorta. It does not receive blood directly from the umbilical vein.

Clinical Relevance

Nursing practice connection: Knowing Fetal Circulation helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses must be able to assess a newborn's transition from fetal to neonatal circulation. This includes listening for heart murmurs, which can be transient as the ductus arteriosus and foramen ovale close.
Maintaining a newborn's temperature is critical. Cold stress increases oxygen demand and can cause pulmonary vasoconstriction, which may lead to a return to fetal circulation patterns (persistent pulmonary hypertension of the newborn).
What if? If a newborn has a large patent ductus arteriosus (PDA) that doesn't close, the nurse would expect to hear a continuous 'machinery-like' murmur and might observe signs of heart failure, such as poor feeding and rapid breathing, due to the shunting of blood from the aorta back to the pulmonary artery.

How to Approach the Question

First, identify the key terms in the question: 'oxygenated blood', 'fetal circulation', and 'umbilical vein'. This directs you to the topic of how the fetus receives oxygen.
Recall the three major shunts in fetal circulation: ductus venosus, foramen ovale, and ductus arteriosus.
Visualize or recall the path of blood from the placenta. The umbilical vein carries oxygenated blood into the fetal body.
Consider the function of each shunt. The ductus venosus specifically deals with blood from the umbilical vein and its entry into the central circulation.
Eliminate the other options based on their known functions: the ductus arteriosus bypasses the lungs, and the intrahepatic vessels are part of the liver's internal circulation, not the main shunt.

Concept Tested & Keywords

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E6 Anatomy Grays 43e Vol 1 Part 2 pp. 54-56, 56-58, 57-59