

The muscle fibers of the pectoralis end in a flat tendon, which is inserted into a groove called the intertubercular sulcus, in the upper humerus located in the upper arm.
The pectoralis major controls various actions to move the shoulder joint:
- Clavicular head flexes the humerus, as in throwing an underhand ball
- Sternocostal head adducts the humerus, as when flapping the arms
- Pectoralis major medially rotates the humerus, as when arm wrestling
- Pectoralis major keeps the arm attached to the trunk