Parietal Bone: Anatomy, Borders And Surfaces | Kenhub

Borders

Sagittal suture Sutura sagittalis 1/4 Synonyms: none

The parietal bone has four borders which articulate with the surrounding skull bones via various sutures. These borders include;

• Sagittal border, located superiorly. It is the thickest and longest out of all of them. The two parietal bones articulate at the sagittal borders with each other to form the sagittal suture.  
• Squamosal border, situated inferiorly. The border starts thin and straight anteriorly, arches in the middle and then thickens posteriorly. The squamosal border comes in contact with three bony structures. From anterior to posterior these are the greater wing of the sphenoid bone and the squamous and petrous parts of temporal bone. These articulations form the sphenoparietal and parietomastoid sutures.
• Frontal border, located anteriorly. It is the most serrated margin of the parietal bone. It comes in contact with the frontal bone to form the superolateral half of the coronal suture. 
• Occipital border, located posteriorly. It is also highly irregular and forms the inferolateral half of the lambdoid suture by articulating with the occipital bone.

The parietal bone has four angles;

• Frontal angle pointing anterosuperiorly. It is formed by the intersection of the sagittal and frontal borders. The frontal angle is located at the bregma, which represents the intersection of the sagittal and coronal sutures.
• Sphenoidal angle facing anteroinferiorly. It is created by the union of the frontal and squamosal borders. The sphenoidal angle is situated at the pterion, which represents the intersection of the coronal, sphenoparietal and sphenofrontal sutures. 
• Occipital angle which points posterosuperiorly, being more rounded compared to the rest. It is formed by the intersection of the sagittal and occipital borders. The angle is situated at the lambda, which represents the union of the lambdoid and sagittal sutures. 
• Mastoid angle which faces posteroinferiorly. It is created by the intersection of the occipital and squamosal borders. The angle is found at the asterion where the parietomastoid and lambdoid sutures meet.

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