Which of the following bones connects all other bones in the skull?

The sphenoid bone is often referred to as the "keystone" of the skull because it articulates with all other cranial bones, thereby connecting them. Located at the base of the skull, the sphenoid bone has a complex shape that spans across the cranial cavity and interfaces with numerous other bones, such as the frontal, parietal, temporals, occipital, ethmoid, and others. This unique positioning and its ability to connect to various bones make the sphenoid essential for skull integrity and structure.

In contrast, while other bones like the ethmoid, maxilla, and temporal bones perform important functions, they do not share the same connecting role with all other skull bones. The ethmoid bone primarily contributes to the nasal cavity structure, the maxilla is essential for the formation of the upper jaw and teeth, and the temporal bones house structures related to the ear and contribute to the side of the skull, but none of them connect with every other bone in the skull like the sphenoid does.