Development of Skull (Embryology) Flashcards
bones of face and skull come from
neuroectoderm –> neural crest in head –> mesenchyme in pharyngeal arches
base of skull comes from
intraembryonic mesoderm –> paraxial mesoderm –> somitomeres/somites –> sclerotome
= brain case (cranial vault), base of skull
neurocranium
= face; contains taste, sight and smell organs
viscerocranium
The neurocranium forms around the rostral end of the _______
neural tube
The viscerocranium forms around the rostral end of the developing _________
gut tube
Cartilaginous contributions to neurocranium
Cartilaginous (contributes to skull base) → ethmoid, sphenoid, occipital base, petrous temporal, temporal-mastoid
Endochondral ossification (from cartilage)
Membranous contributions to neurocranium
Membranous (contributes to cranial vault) → flat bones of vault = parietal, frontal, squamous occipital
Intramembranous ossification
From ossification center, ossify in radial pattern
cartilaginous viscerocranium
Malleus, incus, stapes, hyoid, temporal-styloid
Endochondral ossification
membranous viscerocranium
premaxilla, maxilla, zygomatic, temporal-squamous, mandible (both)
Intramembranous ossification
fusion of the sagittal suture produces a long front-to-back diameter skull
scaphocephaly
= fusion of coronal & lambdoidal sutures bilaterally produces a “tower skull”
Turricephaly (oxycephaly, acrocephaly)
fusion of coronal suture bilaterally produces a shortened front-to-back diameter of skull (“flat-head”)
brachycephaly
fusion of frontal (metopic) suture producing a median frontal ridge
Trigonocephaly
fusion of coronal &/or lambdoidal sutures unilaterally produces an asymmetrical skull
plagiocephaly
small head due to a brain that fails to grow
microcephaly
skull defect the through which the meninges and/or brain herniate.
cranioschisis
Autosomal dominant genetic disorder characterized by craniosynostosis and other congenital abnormalities e.g., syndactyly of hands and feet, mental retardation.
aperty syndrome
no skull
acrania
no brain
anencephaly
some poorly formed brain stem tissue present
meroanencephaly
Enlarged ventricles due to too much CSF. If this occurs prior to closure of the sutures, the head enlarges.
hydrocephalus
