The sinoatrial (SA) node is located at which anatomical site?

• A. Junction of the right atrium and superior vena cava
• B. Posterior to the tricuspid valve
• C. Superior to the coronary sinus ostium
• D. Forms the anterior wall of the right atrium

Answer: (A)

Anatomical location of the sinoatrial node: it resides in the anterosuperior wall of the right atrium, right where the right atrium meets the superior vena cava. This placement places the pacemaker at the highest point of the atrial wall near the SVC inlet, enabling rapid, widespread atrial activation.

This is why the junction of the right atrium and the superior vena cava is the best description. The other options point to regions associated with other structures: the AV node sits lower in the interatrial septum near the coronary sinus opening, not at the SVC-RA junction; the coronary sinus ostium is down near the posterior-inferior atrial region, which is not where the SA node sits; and the SA node is not part of the anterior wall of the right atrium.