The heart sound heard on the stethoscope when the blood pressure in the artery maximum is due to

Options

A. Closure of semi-lunar valves
B. Closure of atrio-ventricular valves
C. Opening of semi-lunar valves
D. Opening of atrio-ventricular valves

Answer

To solve the question regarding the heart sound heard on the stethoscope when the blood pressure in the artery is at its maximum, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Blood Pressure Phases**:
- Blood pressure in the arteries has two main phases: systole and diastole.
- Systole is when the heart contracts, pumping blood into the arteries, leading to maximum blood pressure.
- Diastole is when the heart relaxes, and the pressure in the arteries decreases.

2. **Identifying Heart Sounds**:
- The heart produces sounds that can be heard through a stethoscope. These sounds are typically referred to as "LUB" and "DUB".
- The "LUB" sound corresponds to the closure of the atrioventricular (AV) valves (which include the tricuspid and bicuspid/mitral valves) at the beginning of systole.
- The "DUB" sound corresponds to the closure of the semilunar valves (pulmonary and aortic valves) at the end of systole.

3. **Maximum Arterial Pressure**:
- The maximum blood pressure in the arteries occurs during the systolic phase of the cardiac cycle.
- This is when the ventricles contract and blood is ejected into the arteries, causing the pressure to rise.

4. **Closure of AV Valves**:
- The closure of the AV valves (tricuspid and bicuspid) occurs at the start of systole.
- This closure prevents backflow of blood into the atria and contributes to the increase in pressure in the ventricles and subsequently in the arteries.

5. **Conclusion**:
- Therefore, the heart sound heard on the stethoscope when the blood pressure in the artery is at its maximum is due to the closure of the atrioventricular (AV) valves during systole.

### Final Answer:
The heart sound heard on the stethoscope when the blood pressure in the artery is maximum is due to the closure of the atrioventricular (AV) valves.

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