The human cranium, or skull, acts as a bony casing that safeguards the delicate structures of the brain. The parietal bones are a pair of large, flat bones that contribute substantially to the cranial vault, the upper dome-shaped portion of the skull. The word “parietal” comes from the Latin word paries, meaning wall, aptly describing their function in forming the walls of the cranium.
Defining the Location on the Skull
The parietal bones are situated on the superior and lateral aspects of the cranium. They form the majority of the roof of the skull and curve down to make up the upper sides. There is one parietal bone on the left side and one on the right, meeting at the midline to form the highest point of the skull’s dome.
Their placement covers the brain’s parietal lobes, which are involved in processing sensory information. Each parietal bone is roughly quadrilateral in shape, featuring a convex outer surface and a concave inner surface.
Understanding the Surrounding Sutures and Bones
The parietal bones connect to five other bones of the skull via specialized, immovable joints called sutures. These connections are serrated, interlocking lines that firmly hold the bones together in adults.
The parietal bones are bordered by four major sutures:
- The sagittal suture joins the two parietal bones to each other along the top-center of the skull.
- The coronal suture connects the anterior edge of each parietal bone to the frontal bone, which forms the forehead.
- The lambdoid suture joins the posterior border of the parietal bones to the occipital bone at the back of the head.
- The squamosal suture connects the inferior edge of the parietal bone to the temporal bone, located above the ear.
Primary Function of the Parietal Bones
The main role of the parietal bones is to provide protection for the underlying brain tissue. By forming the roof and upper sides of the skull, they create a strong, curved barrier against external physical forces, safeguarding the cerebral hemispheres from injury.
The internal surface contains grooves that house the meningeal blood vessels, which supply blood to the protective layers surrounding the brain. The external surface also serves as attachment points for muscles, such as the temporalis muscle, which is involved in chewing.