What is the name of the bone located on the thumb side of the forearm?

The radius is the bone located on the thumb side of the forearm. It runs parallel to the ulna, which is located on the opposite side, or the little finger side of the forearm. The radius is pivotal in allowing for the rotation of the forearm, enabling motions such as pronation and supination, which are those actions where the palm turns up or down.

The other choices refer to different bones. The ulna, while part of the forearm, is positioned opposite the radius, closer to the body, and involves the little finger. The femur is a long bone in the thigh, and the humerus is the bone of the upper arm. Understanding the function and placement of these bones is crucial for grasping the anatomy and movements of the upper limb.