- Origin
- Outer surfaces of the upper 8 or 9 ribs (typically ribs 1–8)
- Insertion
- Anterior (costal) surface of the medial border of the scapula
- Innervation
- Long thoracic nerve (C5–C7), which runs superficially along the muscle
- Blood Supply
- Lateral thoracic artery (from axillary artery)
- Contributions from thoracodorsal and superior thoracic arteries
- Actions
- Protracts the scapula (e.g. pushing, punching)
- Holds scapula against the thoracic wall
- Assists upward rotation of the scapula (important in overhead abduction of the arm >90°)
