Anatomy

Origin

Spinous processes of lower six thoracic vertebrae, spinous processes of all lumbar and sacral vertebrae (through thoracolumbar fascia), supraspinal ligament and iliac crest, outer surfaces of lower three or four ribs, inferior angle of scapula

Insertion

Bottom of intertubercular (bicipital) groove of humerus

Nerve

Thoracodorsal nerve (C6–C8)

Actions

Extends, adducts, and medially rotates the arm; draws the shoulder downward and backward; keeps inferior angle of scapula against the chest wall; accessory muscle of respiration