Parietal bone
Os parietale
Definition
The human skull contains two parietal bones, which form part of the superior and lateral aspects of the cranial vault (the calvaria) or the skull cap. Each parietal bone is shaped like a curved rectangle and has two sides (one external and one internal), four margins (occipital, squamosal, sagittal, frontal), and four corners (frontal, occipital, sphenoidal, and mastoid angles).
Margins:
The two parietal bones meet at the skull’s top middle, along the sagittal suture. On the lateral side, they connect with the temporal bone at the squamosal suture, at the back with the occipital bone at the lambdoid suture, and at the front with the frontal bone to form the coronal suture.
Corners:
The frontal angle is found at the lower front and is the point called the pterion, where four skull bones–the frontal, parietal, temporal, and sphenoid–meet. The mastoid angle is at the lower back, showing an area named the asterion, where the parietal, temporal, and occipital bones come together. The occipital angle is at the back, where the sagittal and lambdoid sutures meet, known as lambda, which in infants is the posterior fontanelle spot. The frontal angle is at the front, where the sagittal and coronal sutures intersect, called bregma, correlating with the anterior fontanelle in infants.
Surfaces:
On the inside, the parietal bones have grooves for the middle meningeal artery, thus playing a crucial role in protecting the brain and its blood vessels. On the outside, the large surfaces of parietal bones serve as attachment sites for the skull muscles.
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Text written by Muhammad A. Javaid, MD, PhD © 2024 IMAIOS.
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