Serratus Posterior Inferior

Written by Sharanya Bhaskaran

Last updated January 5, 2023 • 3 Revisions

The serratus posterior inferior is a muscle within the intermediate compartment of the back. It lies deep to the latissimus dorsi muscle in the lower back.

  • Attachments: Originates from the thoracis and lumbar spines (usually T11 – L3) with the muscle fibres running in a superolateral direction, attaching to ribs 9 – 12.
  • Actions: Depresses ribs 9 – 12.
  • Innervation: Intercostal nerves (T9 – T11) and subcostal nerve (T12).
  • Blood Supply: Supplied by the posterior intercostal arteries, subcostal artery, and upper lumbar arteries.

Fig 1
The intermediate back muscles; serratus posterior superior and inferior.

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