External surface of parietal bone

The external surface of parietal bone is convex, smooth, and has a notable bump near the center called the parietal eminence, showing where the ossification started. Across the middle of the bone, there are two curved lines, known as the superior and inferior temporal lines. The upper line serves as a connection point for the temporal fascia, while the lower line marks the highest point where the Temporalis muscle begins. Above these lines, the parietal bone is covered by a scalp layer called the galea aponeurotica. Below them, it forms part of the temporal fossa, providing an attachment point for the Temporalis muscle.

In the floor of the temporal fossa, the lower front of the parietal bone connects with three other bones: the frontal, temporal, and sphenoid. This connection point is known as the pterion. It is related to the branches of the middle meningeal artery inside the skull. A fracture in this area can tear these arteries, leading to an epidural hematoma.

At the back of the parietal bone, near the sagittal border, there is a tiny opening known as the parietal foramen. This opening allows a vein drain into the large superior sagittal sinus. Sometimes, a small branch of the occipital artery also passes through it.