Spinalis Thoracis Muscle, Posterior View

Description

Running as the most medial column of the erector spinae, the spinalis thoracis appears as long, narrow fascicles immediately adjacent to the thoracic spinous processes, extending superiorly toward the cervical region and inferiorly blending with the lumbar aponeurosis. Lateral to it, the longissimus thoracis forms the intermediate mass of the erector spinae, while the iliocostalis thoracis sits furthest lateral along the rib angles. Superficial layers likely include trapezius spanning the posterior neck and upper thorax, with rhomboid major and minor deep to it and inserting along the medial border of the scapula; latissimus dorsi occupies the posterolateral lower back, and the posterior deltoid and infraspinatus frame the shoulder. Midline is the landmark. Spinalis thoracis matters because its close relationship to the thoracic spinous processes makes it a practical reference when teaching compartmental anatomy of the deep back and when discussing paraspinal pain generators. In thoracic spine surgery and posterior approaches, the erector spinae mass is mobilized off the spinous processes and laminae, and distinguishing the medial spinalis from the more lateral longissimus helps explain why dissection near the midline can still produce postoperative muscle denervation and atrophy via the dorsal rami. The view also supports palpation-based instruction: tenderness just lateral to the spinous processes often implicates deep paraspinal strain rather than scapulothoracic musculature. Use this posterior female back plate for gross anatomy labs covering intrinsic back muscles, rehabilitation texts explaining thoracic extension mechanics, and surgical education materials describing midline posterior exposure of the thoracic spine. It also fits radiology teaching when correlating surface anatomy with axial MRI appearances of the erector spinae columns. Anatomical accuracy verified by SciePro's Medical Advisory Board.