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. Adobe Stock, Licensed to TeachMeSeries Ltd Fig 1The intermediate back muscles; serratus posterior superior and inferior. Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Print Article Rate This Article