Skull Development Flashcards
What are the 2 parts of the skull?
Neurocranium
Viscerocranium
What is the neurocranium?
forms a protective case around the brain
What is the visceromembrane?
Forms the skeleton of the face
What are the 2 parts of the neurocranium?
- Membranous neurocranium
- Cartilaginous neurocranium
What is the membranous neurocranium?
roof and sides of the skull develops from neural crest cells.
They undergo membranous ossification to from flat bones.
Do the membranous neurocranium bones fuse?
No
Allow distortion to pass through the birth canal
How many Fontanelles are there?
6
What process allows the cartilaginous neurocranium to fuse and ossify?
By endochondral ossification
What part of the skull do the cartilaginous neurocranium form?
Form the base of the skull
Cranial base
What is the prechondral chondocranium?
In front of the pituitary gland, delivered from neural crest cells
Where is the Chondral chonrocranium found?
Posterior to pituitary and arise from paradisal mesoderm
What is another name for the cartilaginous neurocranium?
Chondrocranium
Where is the cranial base found?
Underlies the brain
Basilar and lateral occipital, Sphenoid, Ethmoid, Petrous and mastoid parts of the temporal bones)
Name structures, blue, light blue and yellow
What is the vicerocranium mainly formed of?
First 2pharyngeal arches
How many pharyngeal arches are there?
5
1-6
How do the pharyngeal arches form?
Development in a craniocaudal sequence
When do the first pair of pharyngeal arches form?
Day 22
Whe do the 2nd an d3rd pairs of pharyngeal appear?
Day 24
What day do the 4th and 6th pairs of pharyngeal arches form?
Day 29
What is cephalogenesis?
The formation of the head in the developing embryo
What does the early chrondates have?
Notch cord for support
Simple nervous system
Segmented muscle blocks
Branching clefts
What cartilages support the notochord in the head region?
Occipital and parachondral
Does the chrondate have a jaw?
No
Called agnathia
What is the role of the cartilaginous capsule?
To protect sense organs
What modifies to form the jaw?
First arch cartilage
What element becomes the upper jaw?
Palatopterygo quadrants bar
What element becomes the lower jaw?
Meckles cartilage
What forms the TMJ?
Fibrous connection between the upper and lower jaw
How do the additional bony element to protect the skull develop?
This is from the neuroectoderm, from which neural crest cell migrate and differentiate into ectomesenchyme
Name sections A-C of the newborn skull
A - neural crest
B -sclerotome
C - cranial paradisal mesenchyme
What genes play. A role in craniofacial development?
Hox genes
What do the pharyngeal arches rely on for proper development?
Hox genes
What signalling pathways regulate the cal arias growth and cranial suture morphogenesis?
Shh
BMPs
TGF
FGFRsMSX1
Where is the anterior fontanelle found and when does it fuse?
Between the frontal parietal bones
2years
Where is the posterior fontanelle found and when does it fuse?
Between parietal and occipital bones
2-3 years
What are the 4 fontanellles?
Anterior
Posterior
Sphenoid
Mastoid
What is the suture in between the frontal bones?
Metopic suture
What processes are a scent I a new born?
Mastoid and styled processes
What facial nerve may be injured during a foreclosure delivery?
Facial nerve
What is postnatal growth of the skull concerned with?
Development of the vicerocranium
When does the facial skeleton increase usually?
Childhood and puberty
What does the spheno-occipital synchondrosis allow?
Allows anterior posterior growth of the skull
closes around the age of 20
What occurs/forms during the embryonic period?
Pharyngeal arches
Facial development
Ossification centres
What occurs during the fetal period?
Continued ossification
What happens during the post-natal period?
Closure of fontanelle
Growth of facial bones
Growth of skull vault
Expansion of sinuses
Fusion of sutures
Eruption of teeth
Name the cranial sutures
Metopic/frontal suture
Sagitta suture
Coronal suture
Lambdoid suture
Squamosal suture
Name the 8 facial sutures
What is vault growth directly related to?
Brain development
What can problems in brain development effect?
Growth of skull and skull
Compare the growth of the vault size and skull as a whole?
Skull as a whole grows most rapidly from birth to 7th year but vault size increases most during the first year
When does the brain complete its maximum size?
2 years
What is craniosynostosis?
a disorder that involves premature fusion of the cranial vault sutures causing abnormal and disproportionate growth of the cranial bones during development
Describe cephalon disorders
are a group of abnormalities that relate to a wide range of skeletal (skull) and neural (brain) associated defects.
Name neural associated disorders
•Anencephaly, Hydrocephalus, Encephalocele, Colpocephaly (occipital horn enlargement), Lissencephaly (smooth brain), Porencephaly (cyst or cavity in cerebral hemisphere), Acephaly (absence of head), Exencephaly (brain outside skull), Macrocephaly (large head), Micrencephaly (small brain),
Does craniosynostosis occur only in isolation?
No, can show as part of several syndromes
What sutures are associated with non-syndromes craniosynostosis?
Sagittal suture - Scaphocephaly
◦Unicoronal suture - Plagiocephaly
◦Metopic suture - Trigonocephaly
◦Bicoronal sutures - Brachycephaly or Turricephaly or both
How would you identify non-syndromal craniosynostosis?
Classified morphology by the suture involved and subsequent skull shape
What are the side effects of craniosynostosis?
Increased intracranial pressure and development delay is rare
Usually need surgery to correct
What skull shape is common in syndromal craniosynostosis?
Turribrachycephalic skull shape is common
How is craniosynostosis inherited?
All are inherited in an autosomal dominant fashion, except Carpenter syndrome, which is recessive.
What type of craniosynostosis is more common to have developmental delay?
Non-syndromal
What type of craniosynostosis is shown here?
Scaphocephaly
What type of craniosynostosis is shown?
Plagiocephaly
What type of craniosynostosis is shown?
Trigonocephaly
