Widest of the back.
Does THREE things to humerus
Extends, Retracts, and Rotates the humerus Medially.
Forms Posterior Axillary Fold
-large fan shaped and covers most of lower half of back.
-goes from trunk to humerus.
-helps to form posterior axillary fold.
-The latissiumus dorsi extends, adducts , and rotates the humerus medially, such as in scratching the skin in the opposite scapula. take right hand and bring it back to touch scapula on left side. you need to extend humerus, adduct humerus, and rotate it medially.
-working with the pectoralis major, the latismus dorsi is a powerful adductor of humerus. it is important for restoring the upper limb to shoulder from an abducting position like in climbing.
- the latissimus dorsi also raises the trunk to the arm like in doing pull ups.
-to test the latissimus dorsi or it's nerve, the arm is abducted 90 degrees. and when adducted against resistence you can feel the posterior axilarry fold if it is normal.
-Origin: thoraco lumbar or lumbo dorsho fasha. it is a wide band of fasha like an aparossis, which originates of the spinous processes of T7-T12, the lumbar vertebrae, the illiac crest , and sometimes of the inferior angle of scapula.
-The muscle extends laterally and inserts into the intertobucular groove of the humerus.
-it is intervated by the thoracodorsal nerve.
-it's action is that it is a powerful extensor of humerus, a powerful adductor, and a medial rotator of the arm. it also helps to depress the shoulder.