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
- HL
Exam analysis
Chance of appearing10%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper2
Typical marks1–4
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
May 2025Paper2 ["HL"] · TZ34(d)[ 2 ]B3.1.5—Lung ventilation
May 2025Paper2 ["HL"] · TZ110(b)[ 4 ]B3.1.5—Lung ventilation
May 2023Paper1 ["HL"] · TZ219[ 1 ]B3.1.5—Lung ventilation
May 2022Paper1 ["HL"] · TZ221[ 1 ]B3.1.5—Lung ventilation
November 2021Paper2 ["HL"] · TZ04(c)[ 1 ]B3.1.5—Lung ventilation
Practice this objective
Coverage 2013–2025 · 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.