The serratus posterior superior is a muscle within the intermediate compartment of the back. It is a thin and rectangular in shape, and lies deep to the rhomboid muscles in the upper back.
- Attachments: Originates from the lower part of the ligamentum nuchae, and the cervical and thoracic spines (usually C7 – T3). The muscle fibres run in an inferolateral direction, attaching to ribs 2 – 5.
- Actions: Elevates ribs 2 – 5.
- Innervation: Intercostal nerves T2 – T5.
- Blood Supply: Posterior intercostal arteries.