What occurs during exhalation?

During exhalation, the diaphragm and chest muscles relax, which leads to a decrease in the volume of the thoracic cavity. As the diaphragm releases, it moves back up into a dome shape, and the intercostal muscles (which expand the chest during inhalation) also relax. This relaxation results in a drop in pressure within the thoracic cavity compared to the outside atmosphere, allowing air to be expelled from the lungs.

The loss of volume in the thoracic cavity effectively pushes air out of the lungs, facilitating the removal of carbon dioxide and other gases. This process is an essential part of respiration, maintaining gas exchange in the lungs. The simplification of muscle activity during exhalation illustrates the passive nature of this phase under normal conditions, contrasting with the active process of inhalation where muscles contract to draw air in.