Origin: lower part of the lateral border of the Scapula (15) 
Insertion: medial Lip of Intertubercular Sulcus of the Humerus (8)
Actions: Medial Rotation and Adduction of the Humerus
Helping Synergist Muscles:
- with Subscapularis, Deltoid (1) (anterior fibers), Pectoralis Major and Latissimus Dorsi acts to produce the Medial Rotation
- together with Teres Minor, Latissimus Dorsi, Pectoralis Major, Subscapularis and Infraspinatus the arm Adduction
Notes: Teres Major muscle is active during the arm Extension from the flexed position