The human cranium, often referred to as the skullcap, is the bony structure that houses and protects the brain. This vault is composed of several flat, interlocking bones, with the paired parietal bones representing a significant portion of its surface area. These bones are a major component of the neurocranium, the part of the skull that directly surrounds the brain.
Precise Location and Description
The parietal bones are a set of two flat bones, one on the left and one on the right, forming a large area of the superior and lateral aspects of the skull. They are positioned just behind the frontal bone (forehead) and extend backward toward the rear of the head. Each parietal bone is roughly quadrilateral, presenting as a large, slightly curved plate of bone.
Their placement is symmetrical across the midline of the head, a plane known as the sagittal plane. Together, these two bones form a significant part of the calvaria, or the skull roof. The external surface is convex and smooth, and the internal surface is concave, conforming to the shape of the brain.
Connections and Sutures
The boundaries of the parietal bones are defined by specialized, immovable joints known as sutures. Each parietal bone connects with five other major bones of the cranium. The most prominent connection is with its counterpart on the opposite side, where the two parietal bones meet along the top of the skull at the sagittal suture.
Moving forward, the parietal bone connects to the frontal bone at the coronal suture. At the posterior margin, the bone joins the occipital bone (the back of the skull) at the lambdoid suture. Along the side, the parietal bone articulates with the temporal bone via the squamosal suture, and it also meets a small portion of the sphenoid bone near the temple.
Primary Function of the Parietal Bones
The primary function of the parietal bones is to serve as a protective vault for the underlying brain tissue. As part of the skull roof, they form a rigid shield that is highly resistant to external force and trauma. The internal surface of these bones also features grooves that accommodate the middle meningeal artery, providing protection for this important blood vessel that supplies the membranes surrounding the brain.
The bones provide surface area for the attachment of various muscles, such as the temporalis muscle, which is involved in chewing. Crucially, the parietal bones directly protect the parietal lobes of the brain. These brain lobes are responsible for integrating sensory information, including touch, temperature, pain, and spatial awareness.