Question

In humans, blood passes from the post-caval vein to the diagnostic right atrium of the heart due to?

• A. stimulation of the Sinu-auricular node
• B. suction pull
• C. pushing open of the venous valves
• D. pressure difference between the postcaval vein and atrium

Answer 1

The correct option is B

suction pull

The correct option is option B.

Explanation for correct option:

1. Suction pull is the force that pulls the blood from the inferior vena cava of the heart to the right atrium.
2. This causes a pressure difference between the inferior vena cava and the right atrium.
3. The pressure in the right atrium decreases more than in the post caval vein which results in the flow of blood from the post caval vein to the right atrium.

Explanation for incorrect option:

Option A:

1. Sinu-auricular node regulates the rate of heartbeat.
2. Therefore it is often called the pacemaker.

Option C:
The venous valves only open when there is a flow of blood from the veins to the arteries.

Option D:

The pressure difference in the post-caval vein and the right atrium causes a suction pull which in turn causes the blood to flow from the post-caval vein to the right atrium.

Final Answer: In humans, blood passes from the post-caval vein to the diagnostic right atrium due to suction pull.