Parietal bone

The parietal bones (/pəˈraɪ.ɪtəl/) are two bones in the skull which, when joined together at a fibrous joint, form the sides and roof of the cranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named from the Latin paries (-ietis), wall.Figure 1 : Left parietal bone. Outer surface.Figure 2 : Left parietal bone. Inner surface.Left parietal bone (shown in green). Animation stops for a few seconds at inner and outer surface.Skull seen from top. Sagittal suture separates left and right parietal bone.Coronal suture. It separates the parietal bones and the frontal bone.Squamosal suture. It separates the parietal bones and the temporal bone.Lambdoid suture. It separates the parietal bones and the occipital bone.Position of parietal bone (shown in green). Animation.Shape of parietal bone. Animation.Parietal boneCranial bonesSide view of the skull.Base of the skull. Upper surface.Sagittal section of skull.Temporal fossa and parietal boneParietal boneTrajectory of the missile through President Kennedy's skull. The bullet struck posterior part of his right parietal bone from behind.Cephalic extremity.Original mummification. The parietal bones (/pəˈraɪ.ɪtəl/) are two bones in the skull which, when joined together at a fibrous joint, form the sides and roof of the cranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named from the Latin paries (-ietis), wall. The external surface is convex, smooth, and marked near the center by an eminence, the parietal eminence (tuber parietale), which indicates the point where ossification commenced. Crossing the middle of the bone in an arched direction are two curved lines, the superior and inferior temporal lines; the former gives attachment to the temporal fascia, and the latter indicates the upper limit of the muscular origin of the temporalis. Above these lines the bone is covered by the galea aponeurotica (epicranial aponeurosis); below them it forms part of the temporal fossa, and affords attachment to the temporalis muscle. At the back part and close to the upper or sagittal border is the parietal foramen which transmits a vein to the superior sagittal sinus, and sometimes a small branch of the occipital artery; it is not constantly present, and its size varies considerably. The internal surface is concave; it presents depressions corresponding to the cerebral convolutions, and numerous furrows (grooves) for the ramifications of the middle meningeal artery; the latter run upward and backward from the sphenoidal angle, and from the central and posterior part of the squamous border. Along the upper margin is a shallow groove, which, together with that on the opposite parietal, forms a channel, the sagittal sulcus, for the superior sagittal sinus; the edges of the sulcus afford attachment to the falx cerebri. Near the groove are several depressions, best marked in the skulls of old persons, for the arachnoid granulations (Pacchionian bodies).