Internal Oblique

Written by Aren Mnatzakanian

Last updated April 8, 2024 • 7 Revisions •

The internal oblique is a muscle of the anterior abdominal wall. It is a broad, sheet-like muscle, located deep to the external oblique.

  • Attachments: Originates from the inguinal ligament, iliac crest and lumbodorsal fascia. It inserts onto ribs 10-12.
  • Actions: Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso.
  • Innervation: Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.
  • Blood supply: Lower posterior intercostal and subcostal arteries, superior and inferior epigastric arteries, superficial and deep circumflex arteries, posterior lumbar arteries.

    Fig 1
    Lateral view of the abdominal wall. The internal oblique is visible – note that its fibres are perpendicular to those of the external oblique.

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