ABSTRACT
The anatomic structures of the right atrium of importance include the fossa ovalis which is the obliterated ostium secundum. This is surrounded by a limbus or raised area of tissue which encircles the fossa ovalis at all but its inferior mar gin. There is a wide-based, blunt atrial appendage. The Eustachian valve exists as a flap at the orifice of the inferior vena cava and the thebesian valve similarly exists at the orifice of the coronary sinus. There is a crista terminalis which surrounds the base of the right atrial appendage and thus separates the trabeculated from the nontrabeculated portion of the atrium.
