Which of the following bones is NOT part of the axial skeleton?

• A. Skull
• B. Vertebral column
• C. Thoracic cage
• D. Shoulders

Answer: (D)

The axial skeleton forms the central axis of the body, including the skull, vertebral column, and thoracic cage. The shoulders are not part of this central axis; they belong to the appendicular skeleton, which covers the limbs and the girdles that attach them to the trunk. The shoulder girdle—the clavicles and scapulae—connects to the axial skeleton to anchor the upper limbs and enable their movement, but its bones are classified with the appendicular skeleton rather than the axial.