During exhalation, what happens to the diaphragm and external intercostal muscles?

During exhalation, the diaphragm and the external intercostal muscles undergo specific changes in their positions and functions:

1. Diaphragm Relaxation: The diaphragm, which is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity, relaxes during exhalation. When the diaphragm relaxes, it moves upward, returning to its resting position, which causes the thoracic cavity's volume to decrease.

2. External Intercostal Muscles: The external intercostal muscles, which are located between the ribs and assist in elevating the rib cage during inhalation, also relax during exhalation. This relaxation allows the rib cage to move downward and inward, further contributing to the reduction of the thoracic cavity's volume.

The combined effect of the relaxation of the diaphragm and the external intercostal muscles results in a decrease in the lung volume, which increases the internal pressure within the lungs. This pressure difference causes air to be expelled from the lungs, completing the exhalation process.