Which bone forms the sides of the cranium?

The parietal bone is indeed the correct answer as it plays a crucial role in forming the sides of the cranium. Each individual parietal bone is located on either side of the skull and is joined in the middle at the sagittal suture. This configuration is essential for providing structural support to the head and protecting the brain.

In overall cranial anatomy, the parietal bones are particularly significant because they contribute to the lateral walls of the skull. Their large, flat surfaces allow for the attachment of muscles and offer a degree of protection for the internal structures of the brain.

In contrast, the occipital bone is located at the back and bottom of the skull and is primarily responsible for the base of the cranium. The ethmoid bone, located between the eyes and forming part of the nasal cavity as well as the orbits, does not contribute to the lateral sides. The sphenoid bone, positioned at the base of the skull and acting as a keystone by connecting with many other bones, primarily contributes to the floor of the skull rather than the sides. Thus, the parietal bone is uniquely positioned and structured to fulfill the role of forming the sides of the cranium.