Question

In humans, blood passes from the post caval to the diastolic right atrium of heart due to

• A. Pushing open of the venous valves
• B. Suction pull only
• C. Stimulation of the sino-auricular node
• D. Pressure difference between the post caval and atrium and suction pull

Answer 1

The correct option is D Pressure difference between the post caval and atrium and suction pull

Hemodynamically, venous return (VR) to the heart from the venous vascular beds is determined by a pressure gradient (venous pressure - right atrial pressure) and venous resistance (RV). Therefore, increases in venous pressure or decreases in right atrial pressure or venous resistance will lead to an increase in venous return. In diastole, the pressure in the right atrium decreases than the postcaval vein. Hence, blood flows from post caval into the right atrium through suction pull.