Which anatomical structure is NOT part of the shoulder rotator cuff?

The shoulder rotator cuff is a group of muscles and their associated tendons that help stabilize and move the shoulder joint. It is composed of four main muscles: the subscapularis, supraspinatus, infraspinatus, and teres minor. These muscles work together to allow for a wide range of motion in the shoulder while providing support and stability during various movements.

The deltoid muscle, while significant in shoulder movement, is not considered part of the rotator cuff. It primarily functions to abduct the arm and give the shoulder its rounded shape. The trapezius muscle, which is located in the upper back, plays a role in moving the scapula and supporting arm movement, but it is also not part of the rotator cuff composition.

Since the question asks for the anatomical structure that is not included in the rotator cuff, the trapezius muscle stands out as it does not participate directly in the stabilization or movement of the shoulder joint in the same manner as the rotator cuff muscles. Thus, identifying the trapezius muscle as the correct choice highlights the distinction between the primary rotator cuff components and surrounding muscles involved in shoulder mechanics.