What is the bony structure that encases the brain?

The bony structure that encases the brain is referred to as the skull. The skull serves several critical functions, including protecting the brain from injury and providing a structure for the attachment of facial muscles. It comprises two main parts: the cranial bones, which protect the brain, and the facial bones that form the structure of the face.

While the term "cranium" specifically describes the portion of the skull that encloses the brain, the broader term "skull" encompasses both the cranial portion and the facial bones. Therefore, while both terms are related, "skull" is the more accurate answer in this context as it includes the entirety of the structure that encases the brain.

The mandible, which is the lower jawbone, does not provide any protective function for the brain, and the sphenoid is a small bone situated at the base of the skull that contributes to the skull structure but does not encapsulate the brain by itself. Thus, the choice of "skull" effectively captures the full protective structure surrounding the brain.