Latissimus Dorsi

Description

Posterior trunk anatomy centers on the latissimus dorsi, a broad superficial muscle sweeping superolaterally from the thoracolumbar fascia and spinous processes of the lower thoracic and lumbar vertebrae, the posterior iliac crest, and the inferior ribs toward the axilla. Near the posterior axillary fold, its fibers converge into a tendon that spirals anteriorly around the inferomedial border of teres major to insert on the floor of the intertubercular sulcus (bicipital groove) of the humerus. Deep landmarks remain readable beneath the muscle mass, including the vertebral column in the midline, left scapula lateral to the thorax, ribs curving anterolaterally, and the superior pelvis at the lumbosacral junction. The twist matters. That spiraled tendon explains why the latissimus dorsi acts as a powerful shoulder extensor, adductor, and internal rotator while also contributing to scapulohumeral rhythm through its fascial continuity with the thoracolumbar fascia and, indirectly, the pelvis. Surgeons and anatomists track the muscle’s superolateral border to the posterior axillary fold when planning a latissimus dorsi flap for breast reconstruction or coverage of posterior trunk defects, keeping the thoracodorsal nerve and vessels protected along the deep surface near the axilla. Sports clinicians see the same anatomy in overhead athletes, where lat strain or enthesopathy at the humeral insertion can mimic teres major injury and present as posterior axillary pain during resisted adduction and extension. Use this posterior back illustration for gross anatomy teaching on superficial back muscles, for surgical atlases covering axillary approaches and flap harvest, and for rehabilitation resources addressing shoulder extension and pulling mechanics in rowing, climbing, and swimming. It also supports figure annotation in textbooks that need clean relationships between the scapula, ribs, thoracolumbar fascia, and the latissimus dorsi tendon trajectory. Anatomical accuracy verified by SciePro's Medical Advisory Board.