Which of the following structures is not part of the axial skeleton?

The clavicle is classified as part of the appendicular skeleton rather than the axial skeleton. The axial skeleton comprises the bones that form the long axis of the body, including the skull, vertebral column, ribs, and sternum. It serves to support and protect vital organs, including those in the head, neck, and thorax.

On the other hand, the clavicle, or collarbone, connects the arm to the body and is involved in the structure of the shoulder girdle. This makes it a key component of the appendicular skeleton, which includes the limbs and the girdles (pectoral and pelvic) that attach them to the axial skeleton.

In contrast, the mandible (the jawbone), sacrum (part of the vertebral column), and sternum (part of the rib cage) are all integral components of the axial skeleton, providing structure and support to the body’s core.