Which bone forms the upper sides of the head?

The parietal bone is responsible for forming the upper sides of the head. It is one of the major bones of the skull, situated on either side of the head and joined at the top and back by the sagittal and lambdoid sutures respectively. The parietal bones provide structural support and enclose the brain, contributing significantly to the overall shape of the skull. Their flat structure mirrors the rounded contour of the head, making them integral to the protection of the cranial cavity and the brain.

In contrast, the frontal bone forms the forehead and the front part of the skull, while the temporal bone is located on the sides of the skull, above the ears, and plays a role in protecting the temples and housing structures within the ear. The occipital bone, located at the back of the head, is crucial for providing support for the skull and housing the foramen magnum, through which the spinal cord passes. Each of these bones has a specific role and location, but the parietal bones distinctly form the upper sides of the head, making them the correct choice for this question.