The ventilation movements of the lungs in mammals are governed by

Options

A. muscular walls of lung
B. diaphram
C. costal muscles
D. both (b) and (c)

Answer

**Step-by-Step Solution:**

1. **Understanding Ventilation Movements**:
- Ventilation in mammals refers to the process of inhaling and exhaling air, which involves the exchange of oxygen and carbon dioxide.

2. **Inhalation Process**:
- During inhalation, the diaphragm, a dome-shaped muscle located at the base of the thoracic cavity, contracts and moves downward.
- Concurrently, the intercostal muscles (also known as costal muscles) between the ribs contract, causing the rib cage to expand and move upward.
- This expansion of the thoracic cavity decreases the pressure inside the lungs, allowing air to flow in from the atmosphere.

3. **Exhalation Process**:
- During exhalation, the diaphragm relaxes and moves back to its original position (upward).
- The intercostal muscles also relax, leading to a downward movement of the rib cage.
- This relaxation reduces the volume of the thoracic cavity, increasing the pressure inside the lungs and forcing air out.

4. **Identifying the Governing Muscles**:
- The primary muscles responsible for the ventilation movements are the diaphragm and the intercostal (costal) muscles.

5. **Conclusion**:
- The ventilation movements of the lungs in mammals are governed by both the diaphragm and the intercostal muscles.

**Final Answer**: The ventilation movements of the lungs in mammals are governed by both the diaphragm and the intercostal muscles.

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