| Aspect | Inspiration | Expiration |
| Mechanism | Breathing in air | Breathing out air |
| Nature of process | Active process | Passive process |
| Muscles Involved | · Diaphragm · External intercostal muscles | Passive expiration involves no muscle contraction |
| Effect on chest volume | Chest cavity volume increases | Chest cavity volume decreases |
| Effect on Pressure | Chest cavity pressure decreases | Chest cavity pressure increases |
| Movement of air | Air is drawn into the lungs | Air is expelled from the lungs |
| Role of Diaphragm | Contracts and moves downward | Relaxes and moves upward |
| Role of Intercostal Muscles | External intercostals may assist in expanding the ribcage | Internal intercostals may assist in reducing the ribcage |
| Role of Abdominal Muscles | Generally not involved in normal breathing | May contract during forceful expiration |
| Role in gaseous exchange | Facilitates oxygen uptake into the bloodstream | Facilitates carbon dioxide removal from the bloodstream |
Comparison between Inspiration and Expiration
Let me share with you a comparison between Inspiration and Expiration.