The Intermediate Back Muscles - Podcast Version 0:00 / 0:00 1x 0.25x 0.5x 0.75x 1x 1.25x 1.5x 1.75x 2x The muscles of the back can be divided into three groups – superficial, intermediate and intrinsic: Superficial – associated with movements of the shoulder. Intermediate – associated with movements of the thoracic cage. Deep – associated with movements of the vertebral column. The deep muscles develop embryologically in the back, and are thus described as intrinsic muscles. The superficial and intermediate muscles do not develop in the back, and are classified as extrinsic muscles. This article is about the anatomy of the intermediate back muscles – their attachments, innervations and functions. 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 Intermediate Group The intermediate group contains two muscles – the serratus posterior superior and serratus posterior inferior. These muscles run from the vertebral column to the ribcage, and assist with elevating and depressing the ribs. They are thought to have a slight respiratory function. Serratus Posterior Superior The serratus posterior superior is a thin, rectangular shaped muscle. It lies deep to the rhomboid muscles on the upper back. Attachments: Originates from the lower part of the ligamentum nuchae, and the cervical and thoracic spines (usually C7 – T3). The fibres pass in an inferolateral direction, attaching to ribs 2-5. Actions: Elevates ribs 2-5. Innervation: Intercostal nerves. Serratus Posterior Inferior The serratus posterior inferior is broad and strong. It lies underneath the latissimus dorsi. Attachments: Originates from the thoracic and lumbar spines (usually T11 – L3). The fibres pass in a superolateral direction, attaching to ribs 9-12. Actions: Depresses ribs 9-12. Innervation: Intercostal nerves. Adobe Stock, Licensed to TeachMeSeries Ltd Fig 1The intermediate back muscles; serratus posterior superior and inferior. Pro Feature - Dissection Atlas The superficial and intermediate muscles of the back The superficial and intermediate muscles of the back You've Discovered a Pro Feature Access our Dissection Image Library Enhance your understanding with high-resolution dissection images showcasing real-life anatomy. Learn More Do you think you’re ready? Take the quiz below Pro Feature - Quiz The Intermediate Back Muscles Question 1 of 3 Submitting... Skip Next Rate question: You scored 0% Skipped: 0/3 1800 More Questions Available Upgrade to TeachMeAnatomy Pro Challenge yourself with over 1800 multiple-choice questions to reinforce learning Learn More Frequent questions What are the intermediate back muscles and their primary functions? The intermediate back muscles consist of the serratus posterior superior and serratus posterior inferior, which primarily assist with elevating and depressing the ribs. They play a role in respiratory movements by facilitating rib motion during breathing. Where do the serratus posterior superior muscles originate and insert? The serratus posterior superior originates from the lower part of the ligamentum nuchae and the cervical and thoracic spines, typically from C7 to T3, and inserts onto ribs 2-5. This positioning allows the muscle to effectively elevate these ribs. How does the serratus posterior inferior contribute to rib movement? The serratus posterior inferior aids in depressing ribs 9-12, facilitating exhalation. This muscle originates from the thoracic and lumbar spines, usually from T11 to L3, allowing for effective rib depression. What is the innervation of the intermediate back muscles? Both the serratus posterior superior and serratus posterior inferior are innervated by the intercostal nerves. This innervation is essential for their functional role in rib movement during respiration. How do the intermediate back muscles differ from deep back muscles? The intermediate back muscles are classified as extrinsic muscles, as they do not develop in the back, unlike the intrinsic deep muscles that are embryologically derived from the back. The intermediate muscles primarily assist with thoracic cage movements, while deep muscles are involved in vertebral column movements. Rate This Article