OS III, Ex II, skull, pharyngeal arches and face Flashcards
To main parts of skull
neurocranium- holds brain, and visocranium - face and anterior neck.
How are the cartilagious parts of skull formed?
enchondrol ossification
How aer the membranous bones of skull formed
intramembranous ossification
What parts of neurocranium are cartilaginous?
chondrocranium, the cranial base bones
What parts of viserocranium are cartilaginous?
ossicles, hyoid bone
What parts of viserocranium are membranous?
face bones
what three factors help derive skull bones and cartilage
1) outer epithelial layers, 2) mesodermal somites, 3) neural crest cells migrating from neural tube area
what guides the eventual shape of skull?
the soft tissues of the brain, CT and muscle around it.
What are the membranous parts of the neurocranium
Vault bones (ones over top) and fotanells that span bones
how is the cranial base formed?
cartilage islands fuse , ethmoid, sphenoid, petrous temporal, occipital bones are turned to bone via enchondrial ossification
What type of joints between the bones of the cranial base?
synchondrosis types so that they can grow longer and laterally
when does the spheno ethmoid and spheno- occipital joints close
in mid teens,
What happens in the mid teens?
spheno - ethmoid and spheno occipital joints close making longtudinal growth no longer possible
What bones determine the width of the skull?
temporal and sphenoid bones with their lateral growth.
what forms the cranial base angle between occipital and sphenoid bones
Remodeling of sphenoid bone that alignes with cephalic ancle of neural tube.
What predicts mandible position and susceptibality to malocclusions
cranial base angle between occipital and sphenoid bones
Large angel causes what?
under bite
Small angel causes what?
under bite, angle pushes jaw more forward