Development of Skull Flashcards
What is a synchondrosis?
Where is it found and what is an adult example?
A primary cartilaginous joint –Mainly found in the developing skeleton (e.g. growth plates).
Adult example – between first rib and sternum. Hyaline cartilage between the two bone surfaces with very little movement permitted.
Where would you expect to see the Spheno-occipital synchondrosis?
what is unique about this joint?
Between the sphenoid and occipital bones – allows growth in the base of the skull.
it has a mixture of intramembranous and endochondral ossification
What is an ossification centre?
What is a primary osstification centre?
Ossification centers are sites where bone growth/ossification begins.
The first ossification centre to appear is the primary ossification centre.
How many ossification centres does the occipital bone develop from?
Usually 6 ossification centres – parts 3 & 4 usually fused by birth
What is a fontanelle and why are these important structures in the developing skull?
Fontanelles are soft, membranous gaps between the skull bones in an infant’s neurocranium.
Allow molding of the skull during birth and permit continued brain growth after birth.
What fontanelles are there and when do they close?
6
1x Anterior (last to close - 2 years)
1x Posterior (1-3 months)
2x Mastoid (posterolateral) (6-18 months)
2x Sphenoidal (anterolateral) (6 months)
6 in total
fetuses only have anterior/posteior
Are sutures just the joinings made by the fontanelle gaps?
Sutures are fibrous joints between the fused cranial bones with little movement allowed.
Fontanelles are membrane-covered gaps that are later replaced by sutures as the bones fuse.
What sutures do adults have and what do fetuses have in addition?
Coronal
Saggital
Lambdoid
Fetuses have the metopic suture (midline of forehead)
Why are the proportions different in the fetal skull?
For birth compression and brain in early life requires a lot of room to grow
This proportion evens out as the facial skeleton “catches up” in growth postnatally to accommodate the developing dentition.
Compare the angle of the mandible – this is much more obtuse in the fetal skull – what causes the change in the angle of the mandible?
forward and downward growth of mandible to accommodate developing dentition
How can you tell if a symphysis is open or closed
little movable fibrocartilaginous joint between two bones that osstifies
If it is completely open you will be able to see the separation between the two bones, when it is completely closed the line between the two joining parts will have disappeared
How can you tell the age of someone from a radiograph if they haven’t developed wisdom teeth/ removed their wisdom teeth?
Use alternative measure of age estimation. They are more accurate in younger patients, and become more difficult as they grow older
How can you tell which teeth have been lost antemortem and postmortem? Is this related to alveolar bone resorption?
Yes.
Teeth lost during life will display evidence of healing and the tooth socket will eventually be filled in with bone. There will also be resorption of the alveolar bone in the region of the missing tooth.
Perimortem/Postmortem there will be no healing and the open tooth socket will be visible.
Compare the two juvenile (non-adult) mandibles.
Look for the mental symphysis – is it open (fibrous) or closed (fused)?
Both are fused (no symphysis, i.e. no suture visible).
Which has a more obtuse angle of mandible? Females or males?
Females generally have a more obtuse angle of mandible. Male mandibles become squarer, with a close to 90 degree angle of mandible, following puberty.