The Lungs and Gas Exchange

The lungs are the organs responsible for gas exchange in humans — taking in oxygen from the air and removing carbon dioxide from the blood. For AQA GCSE Biology, you need to understand the structure of the lungs, the adaptations of the alveoli for efficient gas exchange, and the mechanism of breathing (ventilation). This lesson covers all of these topics in detail.

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Structure of the Gas Exchange System

The gas exchange system is made up of several structures that work together to move air into and out of the lungs:

graph TD
    A[Nose/Mouth] --> B[Trachea — windpipe, lined with cartilage rings]
    B --> C[Bronchi — two tubes, one to each lung]
    C --> D[Bronchioles — smaller branching tubes]
    D --> E[Alveoli — tiny air sacs where gas exchange occurs]
    F[Diaphragm — sheet of muscle below lungs]
    G[Intercostal muscles — muscles between ribs]
    F --> H[Breathing mechanism]
    G --> H