CVS Practice Test

What is the normal percentage of venous blood return carried by the thebesian venous system?

1. 2-5%

2. 5-10%

3. 10-15%

4. 15-20%

The correct answer is: 5-10%

The correct answer of 5-10% accurately reflects the normal percentage of venous blood return carried by the thebesian venous system. The thebesian veins are small veins that drain blood directly from the myocardium (heart muscle) into the left and right atria. Unlike the main venous return pathways, these veins contribute a minor fraction of the total blood returning to the heart. The typical range of 5-10% signifies that while the thebesian venous system plays a role in venous return, it is relatively small compared to the overall mechanisms by which the heart receives blood. Understanding this percentage is important for evaluating cardiac function and understanding how different pathways contribute to the overall circulatory dynamics. Recognizing the contribution of the thebesian system helps in contextualizing how other major venous systems operate and the relative importance of various routes of blood drainage from cardiac tissues.