Origin
Spine T7, spinous processes and supraspinous ligs of all lower thoracic, lumbar and sacral vertebrae, lumbar fascia, post third iliac crest, last four ribs (interdigitating with ext oblique abdominis ) and inf angle of scapula
|  |
Action
Extends, adducts and med rotates arm. Costal attachment helps with deep inspiration and forced expiration
|