Which bone is NOT part of the cranial structure?

The maxillary bone is not part of the cranial structure; rather, it is a facial bone. The cranial bones are those that form the protective case around the brain, consisting of the frontal bone, occipital bone, and sphenoid bone among others. In contrast, the maxillary bone constitutes a significant part of the jaw and supports the upper teeth, making it a key element of the facial skeleton rather than the cranium. Understanding the distinction between cranial and facial bones can help clarify the structural organization of the skull as a whole.