Explain when and how the two sounds of heart are produced.

Explanation

### Step-by-Step Solution:

1. **Understanding Heart Sounds**: The heart produces two distinct sounds during its cycle, commonly referred to as "lub" and "dub." These sounds occur at specific points in the cardiac cycle.

2. **First Heart Sound (Lub)**:
- The first sound, "lub," is a low-pitched sound.
- It occurs when the **bicuspid (mitral)** and **tricuspid valves** close.
- These valves are located between the **auricles (atria)** and **ventricles** of the heart. The bicuspid valve is found between the left atrium and left ventricle, while the tricuspid valve is located between the right atrium and right ventricle.
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