Final answer:
The clavicle is the only direct connection between the pectoral girdle and the axial skeleton, serving as the bridge between the two. It attaches to the sternum and articulates with the scapula, allowing for mobility in the shoulder and upper limb.
Step-by-step explanation:
The only direct connection between the pectoral girdle and the axial skeleton is the clavicle (collarbone). The clavicle is attached on its medial end to the sternum of the thoracic cage, which is part of the axial skeleton, and it articulates with the scapula above the shoulder joint. This connection allows for extensive mobility of the entire pectoral girdle, enhancing movements of the shoulder and upper limb.