Where is the CS ostium located?

Where is the CS ostium located?

• A. Anterior Wall of RA
• B. Lateral RA Wall
• C. Near the Tricuspid Annulus
• D. Posterior Septal Wall of RA

Answer: (D)

The coronary sinus ostium opens into the right atrium at the posteroseptal wall, where the interatrial septum meets the posterior aspect of the right atrium. This location fits because the coronary sinus travels in the posterior atrioventricular groove and drains into the RA through that posteroseptal region, often with the Thebesian valve guarding the orifice. So, it’s not on the anterior or lateral walls of the right atrium—the ostium sits specifically on the posterior septal wall. While it’s in the general vicinity of the tricuspid annulus, the precise description is posteroseptal, reflecting the CS’s course and drainage point.

The coronary sinus ostium opens into the right atrium at the posteroseptal wall, where the interatrial septum meets the posterior aspect of the right atrium. This location fits because the coronary sinus travels in the posterior atrioventricular groove and drains into the RA through that posteroseptal region, often with the Thebesian valve guarding the orifice.

So, it’s not on the anterior or lateral walls of the right atrium—the ostium sits specifically on the posterior septal wall. While it’s in the general vicinity of the tricuspid annulus, the precise description is posteroseptal, reflecting the CS’s course and drainage point.