The Expiration Process: How Air Leaves the Lungs - A Step-by-Step Guide

Expiration is the process of moving air out of the lungs. It is powered by the contraction of the diaphragm and the intercostal muscles.

The order of events that occur during expiration when the lungs are filled with air are as follows:

1. The diaphragm and the intercostal muscles contract.

2. This decreases the volume of the thoracic cavity.

3. The pressure inside the thoracic cavity increases.

4. This forces air out of the lungs through the trachea and the mouth or nose.

5. The diaphragm and the intercostal muscles relax.

6. The thoracic cavity expands and the pressure inside the thoracic cavity decreases.

7. Air flows into the lungs through the trachea and the mouth or nose.

This cycle of inspiration and expiration repeats itself continuously.