Embryology of the Skull and its contents Flashcards
What kind of cell type does the neurocranium form from?
forms from head mesoderm
What kind of cell type does the viscerocranium form from?
branchial arch mesenchyme
What are the two divisions of the neurocranium?
cartilaginous and membranous
How does the cartilaginous neurocranium form?
intracartilaginous ossification
How does the membranous neurocranium form?
intramembranous ossification
What is craniosynostosis?
premature or abnormal ossification of sutures (deforms skull)
What is encephalocele?
when the brain is forced to herniate out through deformed skull
What are the symptoms of spina bifida occulta?
Often asymptomatic; tuft of hair on skin over underlying unfused vertebral arch
What is spina bifida cystica?
a larger defect in closure, when there is a herniation through an unformed bony spinal arch
What is spina bifida with myeloschisis?
the worst scenario - the spinal cord itself is split and open to the outside
What are the 3 primary brain vesicles?
- forebrain
- midbrain
- hindbrain
What are the 3 brain flexures?
- midbrain flexure (cephalic)
- cervical flexure (between hindbrain and spinal cord)
- pontine flexure (roof of hindbrain)
What are the 5 secondary brain vesicles and what do they form from?
FOREBRAIN gives rise to telencephalon and diencephalon
MIDBRAIN gives rise to mesencephalon
HINDBRAIN gives rise to metencephalon and myelencephalon
From what do each of the ventricles of the brain arise?
lateral ventricles: telencephalon
3rd ventricle: diencephalon
4th ventricle: myelencephalon
cerebral aqueduct: mesencephalon
Where do the pons and cerebellum come from?
metencephalon
What does the choroid plexus do?
secretes cerebral spinal fluid into ventricles and spinal canal
What is the part of the brain that “makes us human”, and why?
telencephalon “endbrain”
forms cerebral hemispheres
What is hydrocephalus?
CSF flow is blocked; ventricles enlarge; impairs brain development
The DIencephalon has many DIverticula - name 6
thalamus hypothalamus optic nerves retinas pineal gland infundibulum
What 2 structures meet to form the pituitary? Which is anterior and which is posterior?
Rathke’s pouch (from the stomodeum) and the Infundibulum (diencephalon) MEET and form the pituitary…
Rathke’s pouch = adenohypophysis = anterior
Infundibulum = neurohypophysis = posterior
What is cranium bifidum?
defect in formation of calvaria “split skull”
What can happen when there is cranium bifidum?
MENINGOCELE: meninges herniate through skull defect
What are some defects that happen when the rostral neuropore fails to close?
meroanencephaly, anencephaly: partial or complete failure of brain formation
exencephaly: some or all of brain forms outside skull
polyhydramnios: excessive amniotic fluid
Why is polyhydramnios a red flag?
red flag for neural defects…means that fetus can’t control swallowing
