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Question 674
Anatomy → Region
Classification
Question
SSBAQuestion Header
At the root of the left lung, which relationship correctly distinguishes the phrenic nerve from the vagus nerve?
Question Stem
Select the single best answer.
Options
A
Both nerves pass anterior to the lung root
B
Both nerves pass posterior to the lung root
C
The phrenic nerve passes posterior and the vagus nerve anterior to the lung root
D
The phrenic nerve passes anterior and the vagus nerve posterior to the lung root
E
The phrenic nerve enters the lung root while the vagus terminates above it
Explanation
The left phrenic nerve crosses anterior to the structures forming the root of the left lung, whereas the left vagus reaches the posterior aspect of the lung root. This anterior-posterior relationship is a useful discriminator between the two nerves within the thorax.
Option Validity
A) The vagus passes posterior rather than anterior to the lung root.
B) The phrenic nerve passes anterior rather than posterior to the lung root.
C) This reverses the correct relationship of the two nerves.
E) Neither relationship is described in this way; the phrenic passes anterior to the root and the vagus posterior to it.
Further Reading
Saxena R. Textbook for MRCOG-1. Chapter 2: Anatomy, p.13.