Posterior Superior Serratus

Description

Posterior thoracic musculature is rendered in a female figure with the trapezius reflected to expose the serratus posterior superior deep to it, spanning obliquely from the lower cervical and upper thoracic midline toward the upper ribs. Fibers arise from the nuchal ligament and the spinous processes of C7 to T3 (often extending to T4) and run inferolaterally to insert near the superior borders of ribs 2 to 5, lying superficial to the erector spinae mass and blending with the thoracolumbar and cervical fascia. Superiorly, the muscle relates to the rhomboid minor and levator scapulae near the medial border of the scapula; inferiorly, it transitions into the layered posterior thoracic wall over the costal angles. Fiber direction is clear. Serratus posterior superior is often taught as an accessory inspiratory muscle, but clinically it is more frequently encountered as a source of posterior shoulder girdle and upper thoracic myofascial pain, with trigger points that can refer along the medial scapular border and mimic cervical radiculopathy. Its rib attachments also place it directly in the corridor used for posterior approaches to the upper thorax, where understanding the muscle planes helps with incision planning, avoiding unnecessary denervation, and orienting rib-level procedures near the costotransverse region and adjacent intercostal neurovascular bundles. Surface anatomy matters here, because pain and palpation findings track the costal angles rather than the scapular spine. Use this illustration for gross anatomy lab teaching on superficial-to-deep posterior thoracic layers, for physical therapy and sports medicine materials on scapulothoracic pain patterns, and for anesthesia or surgical references when planning posterior rib access, regional blocks, or rib fracture exposure. Anatomical accuracy verified by SciePro's Medical Advisory Board.