Which part of the skull is referred to as the cranium?

The cranium refers specifically to the bony structure that encases and protects the brain. This includes the top, back, and sides of the skull, comprised of several bones such as the frontal, parietal, occipital, and temporal bones. These elements work together to provide a protective casing for the brain, ensuring that it is shielded from injury while also providing attachment points for muscles and serving as a structure that supports the face.

The lower jaw area, upper jaw area, and facial bones are considered parts of the skull as well, but they are specifically classified as components of the mandible and maxilla, which are not part of the cranium. Therefore, the most accurate answer is the outer structure that protects the brain, which aligns with the definition of the cranium.