B3.1.5—Lung ventilation
Ventilation moves air by coordinated diaphragm and intercostal muscle actions that change thoracic volume, pressure and airflow direction during breathing.
- Syllabus
- First assessment 2025
- Objective
- B3.1.5
- Level
- SL
Exam analysis
Chance of appearing16%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1–3
Common command terms
- Explain
- Outline
- Identify
- Describe
- State
Scoring notes
- Common mistake
- Reversing the pressure change during inhalation by saying contraction raises thoracic pressure.
Recent exam appearances
November 2025Paper2 ["SL"] · TZ34(b)[ 1 ]B3.1.5—Lung ventilation
November 2025Paper2 ["SL"] · TZ34(a)[ 2 ]B3.1.5—Lung ventilation
May 2025Paper1A ["SL"] · TZ316[ 1 ]B3.1.5—Lung ventilation
November 2024Paper2 ["SL"] · TZ15(a)(iii)[ 3 ]B3.1.5—Lung ventilation
May 2024Paper3 ["SL"] · TZ23(b)[ 2 ]B3.1.5—Lung ventilation
Practice this objective
Coverage 2010–2025 · Updated 15 Jul 2026
Concept essentials
- Inhalation occurs when diaphragm and external intercostal contraction increases thoracic volume.
- Lower pressure in the thorax causes air to enter the lungs from higher external pressure.
- Expiration during quiet breathing mainly follows muscle relaxation and elastic recoil.
- Internal intercostal and abdominal muscles contribute to forced expiration.
- Exercise increases ventilation by raising breath depth, breath frequency or both.