Gas exchange in humans — Cambridge IGCSE Combined Science

The parts of the breathing system, how the alveoli are adapted for gas exchange, and how exercise changes the rate and depth of breathing.

Spec B11.1Gas exchange in humans, subtopic 1 of 1

Revision notes

3 short notes, in the order of the specification. Each one in short:

The breathing system
Air passes through the larynx, trachea, bronchi and bronchioles to the alveoli in the lungs; ribs, intercostal muscles and the diaphragm move the thorax.
Features of gas exchange surfaces
Supplement
A good gas exchange surface in humans has four features: a large surface area, a thin surface, a good blood supply and good ventilation with air. In the alveoli, oxygen diffuses into the blood and carbon dioxide diffuses out. Millions of alveoli give a large surface area, and walls one cell thick give a short diffusion distance.
Physical activity and breathing
Practical
During exercise the rate and depth of breathing increase, bringing in more oxygen and removing more carbon dioxide for faster respiration.

2 exam-style questions (7 marks), each with its mark scheme.

9 cards: flip them, mark what you knew, and practise the rest.

The whole of gas exchange in humans on one page, so you can see where this subtopic fits.

Method, variables, risks and a results table, with questions to answer.

Free PDFs to print or save.

Name the tubes that carry air into each lung.
Show answer
Bronchi.
Supplement State the four features of a gas exchange surface in humans.
Show answer
Large surface area, thin surface, good blood supply and good ventilation with air.

Written and checked against the Cambridge IGCSE Combined Science (0653) specification · Updated October 2026