The left atrium and the lateral and posterior surfaces of the left ventricle are supplied by the?

SCTIMST Staff Nurse - 2015 (Set-A)

Applied Anatomy

Easy

Appeared in: SCTIMST Staff Nurse - 2015 (Set-A)

Explanation

The circumflex artery is a branch of the left coronary artery.
It travels in the coronary sulcus (the groove between the atria and ventricles) towards the posterior of the heart.
It gives off obtuse marginal branches that supply the lateral wall of the left ventricle.
It also provides blood supply to the left atrium and the posterior wall of the left ventricle.

Option A: The Left Anterior Descending (LAD) artery supplies the anterior wall of the left ventricle, the apex, and the anterior two-thirds of the interventricular septum, not the lateral and posterior surfaces.
Option B: The Left Coronary Artery (LCA) is the main trunk that divides into the LAD and the circumflex artery. While it is the origin, the circumflex artery is the specific branch that supplies the areas mentioned. This answer is too general.
Option C: The Right Coronary Artery (RCA) primarily supplies the right atrium, right ventricle, the inferior wall of the left ventricle, and the heart's conduction system (SA and AV nodes).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Coronary artery anatomy and myocardial blood supply as background academic context rather than a clinical decision trigger.
Understanding coronary artery territories is crucial for interpreting electrocardiograms (ECGs) during a myocardial infarction (heart attack).
An occlusion (blockage) in the circumflex artery typically causes a lateral or posterior wall myocardial infarction, which would show ST-segment elevation in specific ECG leads (I, aVL, V5, V6 for lateral; ST depression in V1-V3 for posterior).
Nurses must be able to correlate patient symptoms (like chest pain) with ECG findings to anticipate which coronary artery is affected and prepare for appropriate interventions like percutaneous coronary intervention (PCI).

How to Approach the Question

First, read the question carefully and identify the key anatomical structures mentioned: 'left atrium', 'lateral surfaces of the left ventricle', and 'posterior surfaces of the left ventricle'.
Next, recall the basic anatomy of the coronary circulation, specifically the three main arteries: Right Coronary Artery (RCA), Left Anterior Descending (LAD), and Circumflex (Cx).
Mentally map the territory supplied by each artery. The LAD supplies the front (anterior), the RCA supplies the right side and bottom (inferior), and the Circumflex supplies the side (lateral) and back (posterior) of the left ventricle.
Evaluate the options based on this mental map. The question asks for the vessel supplying the lateral and posterior LV, which directly corresponds to the territory of the circumflex artery.
Eliminate the other options. The LAD supplies the front. The RCA supplies the right side. The 'left coronary artery' is a main trunk, and 'circumflex artery' is the more specific and correct branch.

Concept Tested & Keywords

Concept Tested: Coronary artery anatomy and myocardial blood supply.
Stem keywords: left atrium, lateral surfaces, posterior surfaces, left ventricle, supplied by
Lead-in keywords: BEST, MOST RELEVANT CLUE

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E6 Anatomy Applied Ashalatha 4e p. 166-168

E6 Medicine Harrison 22e Part 1 p. 1949-1951