Final answer:
The clavicle, or collarbone, is the most commonly broken bone in the human body due to its role in transmitting forces from the arm to the trunk and its susceptibility to fracture when falling onto outstretched arms.
Step-by-step explanation:
Most Commonly Broken Bone in the Human Body
The bone in the human body that is most commonly broken due to its role in transmitting forces from the arm to the trunk is the clavicle (A) Clavicle. The clavicles are S-shaped bones situated horizontally across the front of the thorax just above the first rib, playing a crucial role in positioning the arms on the body. They are especially susceptible to fractures as a result of their location and the forces they encounter. For example, when a person falls onto their outstretched arms, the force is transmitted up to the clavicles, which may break if the impact is severe. The clavicle articulates with the sternum at one end and the scapula (shoulder blade) at the other, functioning as a strut to support the scapula and, by extension, the arm. The clavicle also serves a protective role for the underlying nerves and blood vessels passing from the trunk to the upper limb.
Clavicle fractures often occur between the middle and lateral parts of the bone, with the force typically causing an anterior and medial displacement of the fragments. This displacement, while painful, usually spares the important blood vessels and nerves from damage. The sternoclavicular joint, being strong and rarely dislocated, often results in the clavicle breaking rather than the joint succumbing to injury. When a clavicle fracture is complete, the affected person might support their arm with the other hand due to the drooping caused by the fracture, a visual sign often associated with this condition.