Question

What prevents movement of blood from pulmonary trunk into right ventricle during the ventricular relaxation?

• A. Tricuspid valve
• B. Pulmonary valve
• C. Mitral valve
• D. Aortic valve

Hint:

The closure of the semilunar valves (aortic and pulmonary valves) at the start of ventricular diastole produces the second heart sound ("dub"), while the closure of the AV valves (tricuspid and mitral) produces the first ("lub").

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The mammalian heart contains specialized valves that ensure one-way blood flow through its chambers, preventing backflow during different phases of the cardiac cycle.

Step 2: Detailed Explanation:
Let us review the anatomy and function of the cardiac valves during ventricular diastole (relaxation):
- Right Ventricle and Pulmonary Trunk: During ventricular systole (contraction), the right ventricle pumps deoxygenated blood into the pulmonary trunk through the open pulmonary valve.
When the ventricle relaxes during diastole, pressure inside the right ventricle drops rapidly below the pressure in the pulmonary trunk.
This pressure difference forces blood backward toward the ventricle, which fills the cusps of the pulmonary valve (a semilunar valve) and snaps it shut.
Closing this valve prevents blood from flowing back into the right ventricle from the pulmonary trunk.
Let us identify the other valves to confirm this:
- Tricuspid Valve: Prevents backflow of blood from the right ventricle into the right atrium during ventricular contraction.
- Mitral (Bicuspid) Valve: Prevents backflow of blood from the left ventricle into the left atrium during ventricular contraction.
- Aortic Valve: Prevents backflow of blood from the aorta into the left ventricle during ventricular relaxation.

Step 3: Final Answer:
The pulmonary valve prevents the backflow of blood from the pulmonary trunk into the right ventricle during ventricular relaxation.