Select the statement that is correct related to movement of diaphragm and intercostal muscles for the process of effortless exhalation.

Options

A. Diaphragm relax and external intercostal muscles relax
B. Diaphragm relax and external intercostal muscles contracts.
C. Diaphragm contracts and external intercostal muscles show no movement
D. Diaphragm contracts and external intercostal muscles relax

Answer

To solve the question regarding the movement of the diaphragm and intercostal muscles during effortless exhalation, we can break down the process into clear steps:

### Step-by-Step Solution:

1. **Understanding the Process of Breathing**:
- Breathing consists of two main phases: inhalation (inspiration) and exhalation (expiration).
- During inhalation, the diaphragm and intercostal muscles contract, allowing the lungs to expand and air to flow in.

2. **Focusing on Effortless Exhalation**:
- Effortless exhalation is a passive process. It does not require active muscle contraction.
- During this phase, the diaphragm and intercostal muscles relax.

3. **Movement of the Diaphragm**:
- The diaphragm is a dome-shaped muscle located at the base of the thoracic cavity.
- During effortless exhalation, the diaphragm relaxes and moves upwards, reducing the volume of the thoracic cavity.

4. **Movement of the Intercostal Muscles**:
- The intercostal muscles are located between the ribs and assist in expanding and contracting the rib cage.
- During effortless exhalation, the external intercostal muscles also relax, allowing the rib cage to return to its resting position.

5. **Conclusion**:
- Therefore, during effortless exhalation, both the diaphragm and the external intercostal muscles are in a relaxed state.
- The correct statement regarding the movement of the diaphragm and intercostal muscles during effortless exhalation is: "Diaphragm relaxes and external intercostal muscles also relax."

### Final Answer:
The correct statement related to the movement of the diaphragm and intercostal muscles for the process of effortless exhalation is: **Diaphragm relaxes and external intercostal muscles relax.**

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