ANATOMY

Detailed explanation-1: -The pectoralis major extends across the upper part of the chest and is attached to a ridge at the rear of the humerus (the bone of the upper arm). Its major actions are adduction, or depression, of the arm (in opposition to the action of the deltoideus muscle) and rotation of the arm forward about the axis of the body.

Detailed explanation-2: -The main function of this chest muscle as a whole is the adduction and internal rotation of the arm in the shoulder joint.

Detailed explanation-3: -The function of the pectoralis major is different for its different heads. The clavicular head flexes the humerus, and the sternocostal head adducts the humerus. As a whole the action is to adduct and medially rotate the humerus. It also draws the scapula anteriorly and inferiorly.

Detailed explanation-4: -It originates from the outer third of the ribs and inserts onto the front of the scapula (shoulder blade). The pectoralis minor muscle is responsible for moving the scapula forward and downward, and it also assists in adduction (bringing the arm towards the body) and internal rotation of the arm.

Detailed explanation-5: -Function. The primary actions of this muscle include the stabilization, depression, abduction or protraction, internal rotation and downward rotation of the scapula.