What is the parietal bone?

What it is

• The parietal bones form, by their union, the sides and roof of the cranium. Each bone is irregularly quadrilateral in form, and has two surfaces, four borders, and four angles. Surfaces. —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; 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 for the ramifications of the middle meningeal vessel; 27 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 ). In the groove is the internal opening of the parietal foramen when that aperture exists.