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B3.3.8 (HL)—Intercostal muscles

Intercostal muscles act antagonistically during ventilation, with external intercostals lifting ribs for inspiration and internal intercostals assisting forced expiration movements.

Syllabus
First assessment 2025
Objective
B3.3.8
Level
HL

Concept essentials

  • External intercostal muscles lift the ribs up and out during inspiration.
  • Internal intercostal muscles pull ribs down and in during forced expiration.
  • Intercostal muscles act as antagonistic muscle groups.
  • Changing rib position alters thoracic volume and pressure.
ConceptIB Biology HL