The coronary sinus opens into which chamber of the heart, and what valve guards its opening?

• A Left atrium; no valve
• B Right atrium; Thebesian valve (valve of coronary sinus) ✓
• C Right ventricle; tricuspid valve
• D Right atrium; Eustachian valve

Explanation

The coronary sinus, the largest venous channel of the heart, opens into the right atrium between the tricuspid valve orifice and the opening of the inferior vena cava. Its opening is guarded by the semilunar Thebesian valve (valve of the coronary sinus), which prevents regurgitation during atrial systole. The Eustachian valve guards the inferior vena cava opening in the right atrium and in fetal life directs oxygenated blood toward the foramen ovale. The coronary sinus receives drainage from the great, middle, and small cardiac veins.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.