Valve of coronary sinus
The valve of the coronary sinus (Thebesian valve) is a semicircular fold of the lining membrane of the right atrium, at the orifice of the coronary sinus. It is situated at the base of the inferior vena cava. The valve may vary in size, or be completely absent. It may prevent the regurgitation of blood into the sinus during the contraction of the atrium. This valve may be double or it may be cribriform. It is named for German anatomist Adam Christian Thebesius.