Final answer:
The sternum articulates with the clavicle medially at the sternoclavicular joint, which is the only bony connection between the upper limb's pectoral girdle and the axial skeleton.
Step-by-step explanation:
The bone that articulates with the clavicle medially is the sternum. Specifically, the medial or sternal end of the clavicle articulates with the manubrium portion of the sternum at the sternoclavicular joint. This is the only bony articulation between the pectoral girdle of the upper limb and the axial skeleton. The clavicle, also known as the collarbone, is an S-shaped bone that lies horizontally across the front of the thorax just above the first rib. It is positioned to articulate at one end with the sternum and at the other end with the scapula, thereby playing a crucial role in shoulder movement and upper limb mobility.