Serratus Posterior Inferior - Podcast Version 0:00 / 0:00 1x 0.25x 0.5x 0.75x 1x 1.25x 1.5x 1.75x 2x 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 Frequent questions What is the serratus posterior inferior muscle? The serratus posterior inferior is a muscle located in the intermediate compartment of the back, situated beneath the latissimus dorsi in the lower back region. It plays a role in rib movement during respiration. What are the attachments of the serratus posterior inferior? This muscle originates from the thoracic and lumbar vertebrae, specifically from T11 to L3, and its fibres extend superolaterally to attach to ribs 9 to 12. These attachments facilitate its function in rib depression. What is the primary action of the serratus posterior inferior? The primary action of the serratus posterior inferior is to depress ribs 9 to 12. This action assists in the mechanics of breathing, particularly during forced expiration. Which nerves innervate the serratus posterior inferior? The serratus posterior inferior is innervated by the intercostal nerves T9 to T11 and the subcostal nerve T12. This nerve supply is crucial for the muscle's contraction and function. What is the blood supply to the serratus posterior inferior? The blood supply to the serratus posterior inferior comes from the posterior intercostal arteries, the subcostal artery, and the upper lumbar arteries. This vascular supply is essential for maintaining the muscle's health and function. Rate This Article