Final answer:
The clavicle articulates with the 1st rib indirectly via the costoclavicular ligament, allowing for shoulder mobility and providing a stable connection between the upper limb pectoral girdle and the axial skeleton.
Step-by-step explanation:
The clavicle articulates with the 1st rib through an indirect connection via the costoclavicular ligament. The sternal end of the clavicle, which is also referred to as the medial end, has a triangular shape that articulates with the manubrium part of the sternum forming the sternoclavicular joint. This joint provides the only direct bony connection between the upper limb's pectoral girdle and the axial skeleton. The costoclavicular ligament extends from the sternal end of the clavicle to the first rib, securing it and allowing for mobility of the shoulder by enabling movements in various directions. The clavicle, being an S-shaped bone, lies horizontally across the front of the thorax just above the first rib and, while robust, is prone to fractures from traumatic forces such as a fall.