Final answer:
The pectoral girdle is connected to the axial skeleton at the sternoclavicular joint, where the clavicle articulates with the sternum.
Step-by-step explanation:
The only direct connection between the pectoral girdle and the axial skeleton is where the clavicle, or collarbone, articulates with the sternum. This point of union is specifically at the sternoclavicular joint. The clavicle is an S-shaped long bone that serves as a strut between the shoulder blade, or scapula, and the sternum of the thoracic cage, which is part of the axial skeleton. Moreover, the clavicle is anchored to the axial skeleton via a single, highly mobile joint, allowing extensive mobility of the pectoral girdle and enhancing movements of the shoulder and upper limb.