During expiration, the diaphragm becomes

Options

A. dome-sphaped
B. oblique
C. concave
D. flattened.

Answer

**Step-by-Step Solution:**

1. **Understanding Breathing Phases:**
- Breathing consists of two main phases: inspiration (inhaling) and expiration (exhaling).
- During inspiration, air is drawn into the lungs, while during expiration, air is expelled from the lungs.

2. **Role of the Diaphragm:**
- The diaphragm is a dome-shaped muscle located beneath the lungs. It plays a crucial role in the mechanics of breathing.
- When the diaphragm contracts, it flattens, increasing the volume of the thoracic cavity and allowing air to enter the lungs.

3. **Diaphragm during Inspiration:**
- During inspiration, the diaphragm flattens to create more space in the thoracic cavity, which lowers the pressure inside the lungs and draws air in.

4. **Diaphragm during Expiration:**
- During expiration, the diaphragm relaxes and returns to its original dome shape.
- This change in shape decreases the volume of the thoracic cavity, increasing the pressure in the lungs and forcing air out.

5. **Conclusion:**
- Therefore, during expiration, the diaphragm becomes dome-shaped again. The correct answer to the question is that during expiration, the diaphragm becomes **dome-shaped**.

**Final Answer:**
- During expiration, the diaphragm becomes **dome-shaped**.

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