from The Century Dictionary.
- noun In craniometry, the region where the frontal, squamosal, parietal, and sphenoid bones meet or approach one another.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun anatomy The point corresponding with the
posteriorend of the sphenoparietal suture; known as the weakestpart of the skull.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun the craniometric point in the region of the sphenoid fontanelle
from Wiktionary, Creative Commons Attribution/Share-Alike License
Injuries like this usually happen to the thin area in the temple called the "pterion".
The squamosal suture arches backward from the pterion and connects the temporal squama with the lower border of the parietal: this suture is continuous behind with the short, nearly horizontal parietomastoid suture, which unites the mastoid process of the temporal with the region of the mastoid angle of the parietal.
One, the pterion ossicle, sometimes exists between the sphenoidal angle of the parietal and the great wing of the sphenoid.
At the tip of the great wing is a triangular portion, bevelled at the expense of the internal surface, for articulation with the sphenoidal angle of the parietal bone; this region is named the pterion.
In order to mark out the lateral cerebral (Sylvian) fissure a point, termed the Sylvian point, which practically corresponds to the pterion, is defined 35 mm. behind and 12 mm. above the level of the frontozygomatic suture; this point marks the spot where the lateral fissure divides.
The point corresponding with the posterior end of the sphenoparietal suture is named the pterion; it is situated about 3 cm. behind, and a little above the level of the zygomatic process of the frontal bone.
Sometimes referred to in neurosurgical circles as "God's little joke", the bony pterion is not just a hazard zone because it is so thin, but also on account of a big artery, the middle meningeal, which runs immediately beneath it.
A direct blow to the pterion, or even an indirect blow to another part of the skull, may cause a fracture to this weak area, with an associated rupture of the underlying vessel.
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The line of the lower margin behind is that of the transverse sinus (see page 1294), or more roughly a line convex upward from the inion to the posterior root of the zygomatic process of the temporal bone; thence along the posterior two-thirds of the upper border of the zygomatic arch where the line turns up to the pterion; the front part of the lower margin extends from the pterion to the glabella about 1 cm. above the supraorbital margin.