What flap of tissue may be seen at the junction of the inferior vena cava and the right atrium?

The Eustachian Valve is a remnant of fetal development that can be observed at the junction of the inferior vena cava and the right atrium. During fetal life, this structure helps direct blood flow from the inferior vena cava toward the foramen ovale, allowing oxygen-rich blood from the placenta to bypass the non-functioning lungs of the fetus. In adults, the Eustachian Valve may not serve a significant function, but its presence is a distinctive anatomical landmark. Its recognition can be important in cardiac imaging for understanding normal anatomical variations as well as for guiding interventions such as catheter placements or other procedures involving the heart.

The other options mentioned do not pertain to the anatomy at this specific junction. The foramen ovale is a fetal structure that closes after birth and is located in the septum between the atria. Helen's Valve and the Coronary Sinus Valve, while relevant in discussions of cardiac anatomy, do not play a role in the specific location described in this question.