The two umbilical arteries carry the ... from the fetus

KGMU 2024

Anatomy and Physiology

Medium

Appeared in: KGMU 2024

Explanation

In the unique environment of fetal circulation, the placenta serves the function of the lungs.
Arteries, by definition, carry blood away from the heart. The two umbilical arteries carry blood away from the fetal heart towards the placenta.
This blood is deoxygenated and full of metabolic waste products, which are transferred to the maternal circulation at the placenta for clearance.
This is the reverse of postnatal systemic circulation, where arteries (except the pulmonary artery) carry oxygenated blood.

Option A: Oxygenated blood is carried from the placenta to the fetus.
Option C: While some mixing of blood occurs at different points in the fetal circulatory system (like the ductus venosus and foramen ovale), the blood collected by the umbilical arteries to be sent to the placenta is primarily deoxygenated.
Option D: The umbilical cord is the lifeline for the fetus, and its vessels are filled with circulating blood.

Visual 1: Diagram - A clear diagram of fetal circulation. The diagram should label the placenta, umbilical cord, umbilical arteries (in blue to indicate deoxygenated blood), and the umbilical vein (in red for oxygenated blood), with arrows showing the direction of blood flow.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Understanding of fetal circulation, specifically the function of the umbilical arteries as background academic context rather than a clinical decision trigger.
At birth, it is standard practice for the nurse or provider to examine the cut umbilical cord to confirm the presence of two arteries and one vein (AVA).
The absence of one umbilical artery, known as a single umbilical artery (SUA), can be a soft marker for other congenital anomalies, particularly cardiac, renal, or gastrointestinal defects, and may warrant further investigation.
What if? If a newborn has a single umbilical artery, the nurse should meticulously perform the newborn assessment, paying close attention to signs of cardiac or renal issues, and ensure the pediatrician is aware of the finding for potential further diagnostic workup.

How to Approach the Question

This is a factual recall question about anatomy and physiology.
First, identify the key terms: 'umbilical arteries' and 'fetus'.
Recall the principles of fetal circulation. Remember that the placenta acts as the lungs for the fetus.
Remember the fundamental definition of an artery: it carries blood AWAY from the heart. The umbilical arteries carry blood away from the fetal heart to the placenta.
Since the blood is going TO the placenta to pick up oxygen, it must be deoxygenated.
Contrast this with the umbilical vein, which carries oxygenated blood FROM the placenta TO the fetus. This 'reversal' is a key concept to remember for exams.

Concept Tested & Keywords

Concept Tested: Understanding of fetal circulation, specifically the function of the umbilical arteries.
Stem keywords: umbilical arteries, fetus, fetal circulation
Lead-in keywords: BEST, MOST RELEVANT CLUE

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