Final answer:
The clavicle, or collarbone, is the bone that transfers forces from the upper limb to the thorax in the shoulder girdle. It attaches the arm to the axial skeleton through sternoclavicular and acromioclavicular joints.
Step-by-step explanation:
The bone in the shoulder girdle that transmits forces from the upper limb to the bony thorax is called the clavicle, or collarbone. The shoulder girdle consists of two main bones: the clavicle in the front and the scapula, or shoulder blade, in the back. The clavicle is an S-shaped bone that plays a crucial role in the pectoral girdle. It attaches medially to the sternum at the sternoclavicular joint, providing a connection to the axial skeleton. Laterally, the clavicle joins with the scapula at the acromioclavicular joint just above the shoulder joint. The clavicle acts as a strut between the scapula and sternum, facilitating the transfer of mechanical forces from the upper limbs to the chest, and provides protection for underlying nerves and blood vessels.