You may be asked about the aspects of processes of inhalation and exhalation.
Inhalation is breathing in
Exhalation is breathing out
Inhalation
- Lungs move upward and outward
- Diaphragm contacts and flattens
- Intercostal muscles contract
- Ribs move upward and outward
- Volume inside thoracic cavity increases
- Pressure inside thoracic cavity decreases
- Air rushes into the lungs
Exhalation
- Lungs move downward and inward
- Diaphragm relaxes and curves upwards
- Intercostal muscles relax
- Ribs move downward and inward
- Volume inside thoracic cavity decreases
- Pressure inside thoracic cavity increases
- Air rushes out of the lungs
Concentration of each gas:
| Gas | Inhaled air | Exhaled air |
| Oxygen | 21% | 16% |
| Carbon dioxide | 0.03% | 4% |
| Nitrogen | 78% | 78% |
