When the intercostal muscles contract, the rib cage moves upwards and outwards , increasing the volume of the chest cavity and helping air enter the lungs.

What exactly happens

  • The external intercostal muscles shorten and pull one rib up toward the rib above.
  • This lifts the ribs so the rib cage swings up and out like a bucket handle being raised.
  • As the ribs rise, the chest cavity becomes larger, so lung volume increases and air is drawn in (inspiration).

In simple exam-style terms:

When the intercostal muscles contract, they raise the ribs, causing the rib cage to move upwards and outwards, increasing thoracic volume to allow inhalation.

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