Latissimus Dorsi, Posterior View

Description

Spanning the posterolateral trunk, the latissimus dorsi forms a broad muscular sheet that converges superolaterally into a thick tendon passing behind the axillary fold to insert on the floor of the intertubercular sulcus of the humerus. Its aponeurotic origin is evident along the thoracolumbar fascia over the lower thoracic and lumbar spinous processes, with inferior fibers arising from the posterior iliac crest and lateral slips from the lower ribs. Medially, the muscle approaches the vertebral column; laterally it sweeps toward the posterior axillary line, where its superior border lies deep to the inferior fibers of trapezius near the midline and deep to posterior deltoid as it nears the shoulder. Big muscle. Clear borders. Posterior views of latissimus dorsi matter because its fiber direction explains a common pattern of function and dysfunction: powerful shoulder extension, adduction, and medial rotation paired with inferior scapular traction when the humerus is fixed. In axillary surgery, the thoracodorsal nerve (C6 to C8) and thoracodorsal vessels enter the deep surface of the muscle near the posterior axillary fold, so this anatomy guides lymph node dissection and helps avoid denervation. The same relationship underpins the pedicled latissimus dorsi musculocutaneous flap used in breast and chest wall reconstruction, where preserving the thoracodorsal pedicle maintains flap viability and bulk. Use this illustration when teaching posterior trunk anatomy in gross anatomy labs, functional kinesiology modules on pulling mechanics, or physical therapy coursework focused on scapulohumeral rhythm and shoulder rehabilitation. It also fits operative atlases and patient education materials for axillary clearance, thoracodorsal nerve injury, and latissimus dorsi flap planning. Anatomical accuracy verified by SciePro's Medical Advisory Board.