Valves in the heart I am confused regarding the presence of valves in the superior vena cava. The superior vena cava does not possess valves unlike inferior vena cava, which possesses Eustachian Valve. Then where are Haversian valves present? Aren't they present at the opening of caval i.e., superior vena cava. Then why is it said that there is absence of valves in superior vena cava?

The purpose of valves is to maintain blood pressure _against gravity_ until it reaches the heart. The Superior Vena Cava (SVC) inlets exist above the heart, and any valves would only prevent gravity from _helping_ bloodflow. The Tricuspid prevents blood from the SVC from just directly flowing into the Right Ventricle.

As a note: The Eustachian Valve either isn't present, or is very small in most individuals as it's only used during development.

Haversian Valves are also found in development, if I remember correctly, and exist when the two vena cavas have yet to separate and mediate bloodflow into the Right Auricle.