Overview
A broad, flat muscle caudal to the scapula. Its fibres converge cranioventrally, pass medial to the long head of the triceps and end in a tendon shared with the teres major.
Origin
Thoracolumbar fascia, which attaches it to the spinous processes of the lumbar and last seven or eight thoracic vertebrae, and muscular slips from the last ribs.
Insertion
Teres major tuberosity (tuberositas teres major) on the medial surface of the humerus.
Action
Flexes the shoulder and draws the limb caudally. With the limb planted, it pulls the trunk cranially.
Innervation
Thoracodorsal nerve (n. thoracodorsalis).
Clinical relevance
Its size and constant vascular pedicle make it a useful muscle flap for reconstructing defects of the thoracic wall.