Negative pressure inside lungs is created due to

Options

A. The contraction of muscles of diaphragm & relaxation of external intercostal muscles
B. The relaxation of muscles of diaphragm & contraction of external intercostal muscles
C. The contraction of muscles of diaphragm & contraction of external intercostal muscles
D. The relaxation of muscles of diaphragm & relaxation of external intercostal muscles

Answer

To answer the question "Negative pressure inside lungs is created due to," we need to understand the mechanics of breathing and the role of specific muscles involved in the process.

### Step-by-Step Solution:

1. **Understanding Pressure and Volume Relationship**:
- According to Boyle's Law, there is an inverse relationship between pressure and volume. When the volume of a container increases, the pressure inside it decreases, and vice versa.

2. **Inhalation Process**:
- The process of inhaling air into the lungs is known as inspiration. This is the first stage of breathing.

3. **Role of the Diaphragm**:
- The diaphragm is a large, dome-shaped muscle located at the base of the thoracic cavity. During inhalation, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity.

4. **Role of Intercostal Muscles**:
- The intercostal muscles, located between the ribs, also play a crucial role. The external intercostal muscles contract during inhalation, lifting the rib cage and further increasing the volume of the thoracic cavity.

5. **Creation of Negative Pressure**:
- As the volume of the thoracic cavity increases due to the contraction of the diaphragm and the external intercostal muscles, the pressure inside the lungs decreases, creating a negative pressure relative to the atmospheric pressure. This negative pressure allows air to flow into the lungs.

6. **Conclusion**:
- Therefore, the negative pressure inside the lungs is created due to the contraction of the diaphragm and the external intercostal muscles during the process of inhalation.

### Final Answer:
Negative pressure inside the lungs is created due to the contraction of the diaphragm and the external intercostal muscles.

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