Final answer:
The majority of IVC blood flow comes from post-capillary venous return from areas such as the gut, kidney, hepatic vein, and lower extremities. This blood flows into the inferior vena cava, which then empties into the right atrium of the heart.
Step-by-step explanation:
The question is concerning the portion of IVC blood flow that is attributed to post-capillary venous return specifically from the gut, kidney, hepatic vein, and lower extremities. While the precise proportion may vary, the majority of blood entering the inferior vena cava (IVC) originates from these areas inferior to the diaphragm before emptying into the right atrium of the heart. It is important to note that systemic venous circulation from areas above the diaphragm generally enters the superior vena cava, with the notable exception being venous blood from the coronary veins that enter directly into the coronary sinus, and then into the right atrium.