BRAINCAKEExhalation
Exhalation (expiration) at rest is mainly a passive process: it happens when the muscles used for inhalation relax, so little extra energy is needed.
During normal exhalation:
• the external intercostal muscles relax, so the ribcage moves downwards and inwards under gravity
• the diaphragm relaxes and is pushed back up into its dome shape by the abdominal organs
• the stretched elastic fibres in the alveolar walls recoil, helping to push air out
• the volume of the thorax decreases
• the pressure in the lungs rises above atmospheric pressure, so air flows out of the lungs
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More in Gas Exchange
- Gas Exchange in the Alveoli
- Adaptations of the Human Gas Exchange System
- Breathing
- Inhalation
- Protecting the Lungs
- Gas Exchange in Insects
- The Tracheal System
- Very Active Insects
All 23 lessons in Gas Exchange · All Edexcel AS-level Biology topics