The Diaphragm in Normal Expiration

The diaphragm is a dome-shaped muscle that separates the chest and abdominal cavities. It plays an important role in breathing, as it contracts and flattens during inhalation and relaxes and arches during exhalation. In normal expiration, the diaphragm is arched.

Explanation:

During normal expiration, the main muscle responsible for breathing out is the diaphragm. As the diaphragm relaxes, it moves upwards towards the chest cavity, creating more space for the lungs to deflate. This movement causes the diaphragm to arch upwards towards the lungs, resulting in an arched shape.

This movement also decreases the volume of the thoracic cavity, which increases the pressure within the lungs. As a result, air is pushed out of the lungs and into the atmosphere.

In contrast, during inhalation, the diaphragm contracts and flattens, moving downwards towards the abdominal cavity. This movement increases the volume of the thoracic cavity, which decreases the pressure within the lungs. As a result, air flows into the lungs from the atmosphere.

Conclusion:

In conclusion, the diaphragm is a vital muscle for breathing, and plays an important role in both inhalation and exhalation. During normal expiration, the diaphragm relaxes and arches upwards towards the lungs, which helps to push air out of the lungs and into the atmosphere.

The correct answer is'A'. Reason:- During inhalation, the muscular part of the diaphragm contact making it flatter and expand the thoracic cavity outwards and downward. When the diaphragm relax the thoracic cavity constricts decreasing the subatmospheric pressure and leading passive egress of air from the respiratory system during the time of exhalation.