All bones have a critical function, and the humerus bone is no exception. In this case, it is a large part of the upper limb. Beginning at the elbow, the humerus is a length of bone extending from above the elbow to the shoulder blade. This is also referred to as the "upper arm bone" because of its location. The top of the humerus touches two major areas: the collar bone and the shoulder blade. Together with various other smaller components, the top of the humerus is able to rotate at the shoulder blade, allow for the arm's range of motion.
Considering the humerus' role in arm function, a fracture can cripple or even negate the functions of the arm. An injury to the upper humerus, where the bone meets the shoulder, can incapacitate that joint. The same applies for the upper arm, which affects the elbow instead.