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Edexcel ·Biology·Cambridge IGCSE Biology

Gas Exchange & Respiration

14 min read

The human breathing system, gas exchange, and aerobic and anaerobic respiration.

The breathing system

Air passes: nose/mouth → trachea → bronchi → bronchioles → alveoli. The trachea is held open by cartilage rings; goblet cells make mucus to trap dust and microbes; cilia sweep it up. Breathing in: the diaphragm flattens, external intercostal muscles raise the ribs, chest volume increases, pressure falls, air rushes in. Breathing out reverses this.

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