Final answer:
The temporal and occipital bones form the lower side and part of the floor of the cranium. The base of the skull is complex and includes these bones along with the frontal, ethmoid, and sphenoid bones, which are all structured to protect the brain as well as provide passageways for nerves and vessels.
Step-by-step explanation:
The bones that make up the lower side of the cranium and part of its floor are known primarily as the temporal and occipital bones. The temporal bone forms the lower lateral side of the skull. According to the passage, the temporal bone is so named because the temple, the region where it is located, is where hair often first turns gray with the passage of time, signaling aging. The cranium or braincase includes several bones, such as the frontal bone, parietal bones, sphenoid bone, and ethmoid bone, in addition to the temporal and occipital bones. Collectively, these bones create a complex surface with various openings for cranial nerves and blood vessels. Specifically, the base of the skull comprises the frontal, ethmoid, sphenoid, temporal, and occipital bones, which form the floor of the cranial cavity.
The cranial floor is subdivided into three regions: the anterior cranial fossa, the middle cranial fossa, and the posterior cranial fossa. The middle cranial fossa is separated from the posterior cranial fossa by the petrous ridge of the temporal bone, a significant structural feature contributing to the overall shape and protective qualities of the cranial base, which encases the brain.