Pectoralis Major

Origin: Clavicle, sternum, and costal cartilages of the upper ribs.

Insertion: Greater tubercle of the humerus.

Action: The pectoralis major muscle is responsible for shoulder flexion, adduction, and medial rotation.

Pectoralis Minor

Origin: Anterior surfaces of the third, fourth, and fifth ribs.

Insertion: Coracoid process of the scapula.

Action: The pectoralis minor muscle is involved in the stabilization and depression of the scapula.