Latissimus dorsi spans across the back arising from the transverse processes of the lower six thoracic vertebrae, the thoracolumbar fascia, the lower four ribs and the iliac crest. It passes superiorly and lateral over the inferior angle of the scapula from where a few fibres may arise.
It wraps around the inferior margin of teres major and forms a tendon which inserts into the floor of the intertubercular groove of the humerus.
Its actions are therefore adduction and medial rotation of the humerus (and extension).
It is innervated by the thoracodorsal nerve and damage to this structure during axillary surgery will result in paralysis of latissimus dorsi and an inability to use the arm to pull the body up.
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