- The curved bone is somewhat quadrilateral, with 2 rather broad surfaces and 4 borders.
- Sagittal Border:
- Upper medial border where the thickest and longest suture forms.
- Joins left and right parietal bones, forming the sagittal suture.
- Squamosal Border:
- Lower border, joining parietal with greater wing of sphenoid bone (sphenoparietal suture) and temporal bone (parietomastoid suture).
- Thin at start, arches slightly along the middle, and thickens posteriorly.
- Frontal Border:
- Most serrated margin.
- Articulates with posterior part of frontal bone.
- Forms coronal suture.
- Occipital Border:
- Articulates with occipital bone.
- Highly serrated, forming the lambdoid suture.
- The External Surface
- This smooth curved surface also shapes the back of the head:
- The superior temporal line is the arch between the occipital and frontal borders; it is where the superficial temporal fascia attaches to the parietal.
- The inferior temporal line is where the temporalis muscle originates.
- Parietal foramina are present at the upper back side of each of the parietal bones, near the sagittal border. These foramina drain into the superior sagittal sinus and allow passage to the occipital artery’s branches.
- The parietal eminence is the central part of the parietal bones, where the bones start to ossify.
- The Internal Surface
- It is the concave inner surface of the bone on the side of the brain. The internal surface is highly irregular to accommodate different blood vessels. The most important of them include the following:
- The arterial grooves, or grooves for the middle meningeal artery
- The grooves for superior sagittal sinus
- The granular foveolae surrounding the groove for superior sagittal sinus and containing arachnoid granulations
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