Serratus Posterior Superior Muscle

Description

Seen from a posterior aspect of the lower neck and upper thorax, the rhomboid minor and rhomboid major are rendered superficially, spanning from the medial border of the scapula to the spinous processes and supraspinous ligaments of the lower cervical and upper thoracic vertebrae. Deep to these scapular retractors lies the serratus posterior superior, a thin quadrilateral muscle whose delicate serrations pass inferolaterally from the nuchal ligament and spinous processes (classically C7 to T3) to the superior borders of ribs 2 through 5 near their angles. Medially, the muscle layers relate closely to the thoracic erector spinae; laterally they approach the scapular region and the posterior rib cage. Layering matters. This posterior dissection-style view helps distinguish scapulothoracic musculature from the costal attachments of the serratus posterior superior, a muscle that is frequently misidentified because it hides beneath the rhomboids and trapezius. Clinically, that distinction comes up when localizing upper thoracic pain and myofascial trigger points that refer along the posterolateral chest wall, or when planning posterior approaches that split the rhomboids to access the upper ribs and intercostal spaces. It also clarifies why serratus posterior superior is described as an accessory inspiratory muscle, while the rhomboids instead control scapular position and can be strained in patients with prolonged protracted-shoulder posture. Use this illustration for gross anatomy lab manuals covering the intrinsic and extrinsic back muscles, for thoracic wall teaching in respiratory mechanics modules, or for surgical education materials discussing posterior rib exposure and scapular retraction during upper thoracic procedures. It also suits radiology correlation notes that explain why superficial muscle bulk can obscure deeper costal slips in posterior imaging and ultrasound. Anatomical accuracy verified by SciePro's Medical Advisory Board.