Which of the following is not one of the five joints that comprise the shoulder girdle?

The shoulder girdle consists of a series of joints that connect the arm to the body, allowing for a wide range of motion and function. The five primary joints in the shoulder girdle are the acromioclavicular joint, the sternoclavicular joint, the glenohumeral joint, and the scapulothoracic joint, among others that assist in stability and movement.

The humeroulnar joint, however, is not part of the shoulder girdle. Instead, it is a hinge joint located in the elbow region, where the humerus of the upper arm meets the ulna of the forearm. This joint primarily facilitates flexion and extension of the elbow, contributing to movements of the forearm rather than the shoulder.

In contrast, the other joints listed, such as the acromioclavicular, sternoclavicular, and glenohumeral joints, play direct roles in connecting the shoulder to the thoracic skeleton and allowing for complex movements of the upper limb. Thus, identifying the humeroulnar joint as not belonging to the shoulder girdle is accurate, reflecting the distinct anatomical separation between these important regions of the upper body.