Where is the SA node located?

• A. At the junction of the superior vena cava and the right atrium
• B. At the AV node in the interventricular septum
• C. In the posterior wall of the left atrium
• D. In the right ventricle near the apex

Answer: (A)

The Sinoatrial (SA) node is the heart’s natural pacemaker, located in the right atrium near the entrance of the superior vena cava. This position places the pacemaker tissue at the top of the atrial conduction pathway, allowing the impulse to quickly spread through the atria and set the heart rate.

The AV node, by contrast, sits in the lower portion of the interatrial septum within the triangle of Koch, near the coronary sinus ostium, not at the SVC-RA junction. The posterior wall of the left atrium and the right ventricle near the apex are not the locations of the primary pacemaker tissue either.

So, being at the junction of the superior vena cava and the right atrium is the correct placement for the SA node.