Expiration

OCR AS-level BiologyExchange Surfaces and BreathingLesson 8 of 24

Expiration is a largely passive process that does not require much energy.

1. The external intercostal muscles relax. The internal intercostal muscles contract. The ribs are pulled downwards and inwards.

2. The diaphragm relaxes causing it to dome upwards, pushed up by the contents of the abdomen.

More in Exchange Surfaces and Breathing

• The Human Gas Exchange System
• The Lungs
• Mechanism of Breathing
• Inspiration
• Alveoli
• Role of Alveoli in Gas Exchange
• Asthma
• The First Breath

All 24 lessons in Exchange Surfaces and Breathing · All OCR AS-level Biology topics