CVS Practice Test 2026 – Complete Exam Preparation

The correct answer is that the thebesian system can carry up to 40% of venous blood return when epicardial venous flow is compromised. The thebesian veins are small veins located within the heart muscle itself, primarily draining deoxygenated blood directly into the chambers of the heart, particularly the left ventricle and right atrium.

In situations where normal venous return pathways are obstructed, such as in cases of compromised epicardial venous flow, the thebesian system becomes particularly important. It can accommodate a larger share of the overall venous return, helping to maintain the balance of blood flow and cardiac function. This capacity can reach as high as 40%, which underscores the significance of the thebesian system in cardiac physiology, especially under stress or compromised conditions.

Other percentage options, such as 20%, 30%, and 50%, do not reflect the physiological capabilities of the thebesian venous system compared to the established understanding of its role in the context of venous return during compromised states.