Origin: Subscapularis Fossa (9) 
Insertion: Lesser Tuberosity of the Humerus (8)
Actions: Medial Rotation and Adduction of the Humerus (arm)
Helping Synergist Muscles:
- together with Pectoralis Major, Latissimus Dorsi, Teres Major, Deltoid (1) (anterior fibers) acts to produce the Medial Rotation
- together with Pectoralis Major, Latissimus Dorsi, Teres Major, Teres Minor, Infraspinatus acts to produce arm Adduction
Notes: together with Supraspinatus, Infraspinatus and Teres Minor joins to form the "Rotator Cuff Muscles"