What is the uppermost and largest bone of the arms?

The uppermost and largest bone of the arms is the humerus. Located in the upper arm, it extends from the shoulder to the elbow and serves as a crucial structure for both mobility and strength in the arm. The humerus also plays a significant role in the operation of the shoulder joint and connects with the scapula at the shoulder joint and the radius and ulna at the elbow joint.

In the context of the other options, the radius and ulna are forearm bones that are located lower than the humerus. The radius is located on the thumb side of the forearm and the ulna on the pinky side. While important for forearm function and movement, neither of these bones is the largest or the uppermost bone in the arm. The sternum, although an essential bone in the chest area, does not belong to the arm structure at all, which further highlights the humerus as the correct answer in terms of the skeletal anatomy of the arms.