What structure is depicted by the head of humerus in upper extremity imaging?

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

Answer: (B)

The head of the humerus is a rounded structure at the proximal end of the humerus that articulates with the glenoid cavity of the scapula, forming the shoulder joint. In upper extremity imaging, when visualizing the head of the humerus, it is primarily assessed in relation to the scapula, which provides the socket into which the head fits. This articulation allows for a wide range of motion at the shoulder joint, including flexion, extension, abduction, and rotation.

In contrast, the clavicle connects the upper limb to the trunk but does not directly articulate with the head of the humerus. The radius and ulna are the two bones of the forearm and are located distal to the humerus. While they are part of the upper extremity, they are not relevant to the structure depicted by the head of the humerus. Therefore, choosing the scapula emphasizes the anatomical relationship that is fundamental to understanding shoulder mechanics and the positioning of the humerus in imaging studies.