Posterior Superior Serratus

Description

Layered over the upper thoracic cage, the serratus posterior superior lies deep to trapezius and the rhomboid major, spanning from the midline spinous processes and supraspinous ligament of C7 to T3 (often including the nuchal ligament) to the posterior aspects of ribs 2 through 5 near their angles. Fibers run inferolaterally, crossing superficial to the erector spinae fascia and approaching the medial borders of the scapulae without attaching to them. Adjacent landmarks include the thoracic vertebrae, posterior ribs, and the scapulae flanking the vertebral column, with the rhomboid major sitting more superficial and medial, tethering the scapula to the spine. Clear bony contrast emphasizes the sheet-like muscle on the posterior thorax. A thin, easily overlooked layer. For teaching posterior thoracic wall anatomy, this muscle matters because it is commonly misidentified as part of the scapular retractors when students rely on surface shape rather than attachments. Surgeons and proceduralists working near the medial scapular border or posterior rib angles (for example, during thoracotomy planning, posterior chest tube placement landmarks, or trigger point injection mapping) benefit from a clean depiction of the serratus posterior superior’s rib insertions, which sit inferior to the scapular spine and lateral to the thoracic spinous processes. Clinically, it also enters discussions of posterior thoracic myofascial pain and accessory respiratory mechanics, where its small excursion contrasts with its frequent implication in pain syndromes. Use this illustration in gross anatomy or kinesiology modules covering the deep extrinsic back muscles, in atlas plates comparing rhomboid major versus serratus posterior superior attachments, or in surgical education materials that orient learners to posterior rib angles and adjacent muscular layers on the male back. Anatomical accuracy verified by SciePro's Medical Advisory Board.