The bone in the upper arm is called the humerus. It is a long bone that extends from the shoulder to the elbow, playing a crucial role in the arm's movement and function. The humerus connects with the scapula (shoulder blade) at the upper end and with the radius and ulna at the lower end, forming the elbow joint. Its structure allows for a wide range of motion, making activities like reaching, lifting, and throwing possible. The humerus is also an important site for muscle attachment, facilitating movements of the forearm and hand.