Which bone forms the long axis of the upper arm?

Which bone forms the long axis of the upper arm?

• A. Humerus
• B. Radius
• C. Ulna
• D. Scapula

Answer: (A)

The humerus sets the straight, central line of the upper limb. It runs from the shoulder to the elbow as a single long bone, forming the main axis of the upper arm. The radius and ulna are in the forearm, not the upper arm, so they don’t define the arm’s axis. The scapula is part of the shoulder girdle and sits apart from the long axis of the arm. Hence, the bone forming the long axis of the upper arm is the humerus.

The humerus sets the straight, central line of the upper limb. It runs from the shoulder to the elbow as a single long bone, forming the main axis of the upper arm. The radius and ulna are in the forearm, not the upper arm, so they don’t define the arm’s axis. The scapula is part of the shoulder girdle and sits apart from the long axis of the arm. Hence, the bone forming the long axis of the upper arm is the humerus.