What happens to the volume of pulmonary cavity
when there is an increase in the volume of thoracic
chamber?

Options

A. It decreases
B. It increases
C. It remains same
D. First decreases and then increases

Answer

To understand what happens to the volume of the pulmonary cavity when there is an increase in the volume of the thoracic chamber, we can break down the explanation into the following steps:

### Step-by-Step Solution:

1. **Understanding the Anatomy**: The lungs are located within the thoracic cavity, which is an airtight chamber. The lungs are surrounded by two membranes: an outer membrane that is in contact with the thoracic lining and an inner membrane that is in contact with the lung surface.

2. **Relationship Between Thoracic and Pulmonary Cavities**: The anatomical arrangement of the lungs and the thoracic cavity is such that any change in the volume of the thoracic cavity will directly affect the volume of the pulmonary cavity. This is because the lungs are not rigid structures; they expand and contract based on the pressure changes in the thoracic cavity.

3. **Effect of Volume Increase**: When the volume of the thoracic chamber increases (for example, during inhalation), it creates a negative pressure within the thoracic cavity. This negative pressure causes the lungs to expand, leading to an increase in the volume of the pulmonary cavity.

4. **Conclusion**: Therefore, when there is an increase in the volume of the thoracic chamber, the volume of the pulmonary cavity also increases. This relationship is crucial for the process of respiration, allowing air to flow into the lungs.

### Final Answer:
When there is an increase in the volume of the thoracic chamber, the volume of the pulmonary cavity also increases.

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