External Intercostals

Written by Oliver Jones

Last updated November 9, 2024 • 4 Revisions

The external intercostals are a muscle of the thoracic wall. They are the most superficial of the intercostal muscles.

Their fibres are orientated in an inferior and anterior direction.

  • Attachments: Originates at the lower border of each rib, inserting onto the superior border of the rib below.
  • Actions: Elevates the ribs and increases the thoracic volume during inspiration.
  • Innervation: Intercostal nerves (T1-T11).
  • Blood supply: Anterior and posterior intercostal arteries.

Fig 1
The external and internal intercostals of the thoracic wall.

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