Latissimus Dorsi Under the Skin, Posterior View

Description

Broad sheets of latissimus dorsi dominate the posterolateral trunk, seen subcutaneously as they sweep from the lower thoracic and lumbar midline toward the posterior axillary fold. Superiorly, the trapezius caps the upper back and frames the medial borders of the scapulae, while the infraspinatus occupies the infraspinous fossa just inferior to the scapular spine. Along the lateral border of the scapula, teres minor sits superior to teres major, and both converge toward the proximal humerus. Medially, the erector spinae columns run parallel to the spinous processes, deep to the superficial back musculature. Clinically, this posterior surface anatomy matters because latissimus dorsi forms a key landmark for the posterior axillary fold and guides dissection planes in axillary surgery, where the thoracodorsal nerve and thoracodorsal vessels course on the deep surface of the muscle near its humeral insertion at the floor of the intertubercular sulcus. Injury or intentional division of the thoracodorsal nerve alters shoulder extension, adduction, and internal rotation, a deficit that becomes obvious during crutch use, climbing, or resisted pulling. The same anatomy explains why the latissimus dorsi musculocutaneous flap remains a workhorse option in breast and chest wall reconstruction, with predictable pedicle location relative to the scapular tip and axillary contents. This is a surgical muscle. Use this artwork in gross anatomy and kinesiology teaching to correlate surface contours with scapulohumeral mechanics, and in operative atlases for axillary lymph node dissection, thoracodorsal pedicle identification, and posterior trunk flap planning. It also fits sports medicine materials that discuss latissimus dorsi strain patterns and posterior shoulder pain related to rotator cuff coupling with teres major. Anatomical accuracy verified by SciePro's Medical Advisory Board.