Parietal bone

The parietal bone (os parietale)is a paired, flat bone which forms the roof of the skull. The parietal bone has two surfaces, four borders, and four angles.

The external surface (facies externa) facing the scalp has the:

Parietal tuber (tuber parietale) or parietal eminence.

Superior temporal line (linea temporalis superior), for the attachment of the temporal fascia.

Inferior temporal line (linea temporalis inferior), for the attachment of the temporal muscle.

The internal surface (facies interna)is concave and turned toward the brain. It presents depressions, the digital impressions (impressiones digitatae) formed by the gyri of the cerebrum, and between them there is a small convex cerebral juga (juga cerebralia). Additionally we can distinguish the:

Groove for sigmoid sinus (sulcus sinus sigmoidei) which is located at the mastoid angle.

Groove for superior sagittal sinus (sulcus sinus sagittalis superioris) which is formed by the sagittal suture connects with the opposite parietal bone where the venous superior sagittal sinus is located.

Groove for the middle meningeal artery (sulcus arteriae meningeae mediae).

Groove for arteries (sulci arteriosi).

Parietal foramen (foramen parietale) which is in the posterior part of the parietal bone, laterally to the superior sagittal groove. It transmits the vein from the superior sagittal sinus.

The parietal bone has four borders:

Sagittal border (margo sagittalis) forms the sagittal suture and lies in the midsagittal plane.

Squamosal border (margo squamosa) forms the inferior margin. The anterior part is short and overlapped by the greater wing of the sphenoid. The posterior part is arched and overlapped by the temporal bone (squamous and mastoid part).

Frontal border (margo frontalis) is the anterior margin, which articulates with the frontal bone forming the coronal suture.

Occipital border (margo occipitalis) is the posterior margin, which articulates with the occipital bone, form ing the lambdoid suture.

The parietal bone has four angles:

Frontal angle (angulus frontalis) is the anterosuperior angle at the bregma. It corresponds to the junction of the sagittal and coronal suture.

Sphenoidal angle (angulus sphenoidalis) is the anteroinferior angle which lies between the frontal bone and the greater wing of the sphenoid bone.

Occipital angle (angulus occipitalis) is the posterosuperior angle which corresponds to the junction of the sagittal and lambdoid suture.

Mastoid angle (angulus mastoideus) is the posteroinferior angle at the lambdoid suture. It connects with the mastoid portion of the temporal bone and occipital bone.