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Now we are going to discuss the norma verticali. This is a young skull, we will find that the
norma verticalis is formed of four bones, frontal bone anteriorly parietal bone on each
side and occipital bone posteriorly. They are separated from each other by sutures,
this is the coronal suture, of course here must be an amount of fibre tissues because
this is a fibrous joint that connects the bones strongly together. This is the coronal
sutures that separates the frontal from the two parietal. The two parietal are separated
from each other by the sagittal suture and the two parietal are separated from the occipital
by lambdoid suture. The point of meeting of the coronal and sagittal, which is the beginning
of the sagittal (the anterior end of the sagittal suture) is called the bregma and the posterior
end of the sagittal suture where it meets the lambdoid suture, this point is called
the lambda. In the newly born instead of these points will have membranes or fontanelles.
This point is the anterior fontanelle and this point is the posterior fontanelle. The
posterior fontanelle transmits into bone at the age of three months and the anterior fontanelle
transmits into bone at the age of eighteen months. The point in the midway between the
anterior fontanelle and the posterior fontanelle is the highest point of the skull and is called
the vertex. In the parietal bone will have an elevation, an area elevated that is called
parietal eminence and of course in the frontal bone also, there will be an elevated region
that is called the frontal eminence. These eminences are very clear in the newly born
because there are the sites of the centres of ossification that will be completely exhausted
in male, therefore they will not be clear in male. In female they will be partially
exhausted and hence will be clear. So if we find these eminence are clear in an adult
skull this will probably be a female skull and if it's not apparent then it will be a
male skull. They are very eminent and very clear in the newly born because they are not
yet exhausted. Also in the newly born will have another suture here inside the frontal
bone dividing it into two like here at this site, this will be called the interfrontal
or the frontal suture or the metopic suture, this suture transmits into bone by the age
of three to six years. Of course this divaricated line denotes the site of the lambdoidal anterior
fontanelle. So the frontal suture in the newly born will terminate into a large membrane
which is the anterior fontanelle. Of course there will be a triangle fontanelle which
is the posterior fontanelle that disappears by the age of three months and the anterior
disappears by the age of eighteen months. This is the sagittal suture and this is the lambdoid
and this is the skull cap and this is the site of the coronal suture. Close to the posterior
end of the sagittal suture we may find a foramen in the parietal bone it may be present in
one side only like this and may be present in both sides or may not be present at all.
This foramen is called parietal emissary foramen and this is for the passage of the parietal
emissary vein that connects the vein of the skull outside to the sinus related to this region. The sinus present here is called
the superior sagittal sinus. Of course if the intracranial pressure is increased more
blood will be taken from the sinus to the outside through this foramen to keep the intracranial
pressure constant so this is a benefit of the vein but if there is an infection in the
scalp, then the infection may be transmitted through the vein to the inside and this will
be a disadvantage of this vein. Therefore the parietal emissary vein is a valveless
vein connecting the veins of the scalp to the superior sagittal sinus. If it is present
then it will have a benefit that when the intracranial pressure increases then it allows
the passage of more blood outside keeping the intracranial pressure constant so this
is an advantage but it is disadvantage if there is an infection in the scalp, that this
infection may be transmitted into the inside of the sinus and may cause thrombosis of this
sinus and the blood may be passed up or down through the emissary vein because the emissary
vein is a valveless vein. This finishes all what about the norma verticalis