neural embryology Flashcards
neural development - process
notochord induces overlying ectoderm to differentiate neuroectoderm and form neural plate —> Neural plate give rise to neural tube and neural crest cells / notochord becomes nucleous pulposus of intervertebral disc in adults
neural development - notochord induces
overlying ectoderm to differentiate neuroectoderm and form neural plate
Neural plate give rise to
neural tube and neural crest cells
neural development - parts of neural tube
alar plate (dorsal): sensory basal plate (ventral): motor SAME ORIENTATION AS SPINAL CORD
from notochord to neural tube - time
day 18-day 21
…. give rise to neural tube and neural crest cells
Neural plate
regional specifications of developing brain - at the beginning - vesicles (number) (cavities)
3 (three primary vesicles)
regional specifications of developing brain - three primary vesicles - parts (Walls)
- forebrain (prosencephalon)
- Midbrain (mesencephalon)
- Hindbrain (rhomboencephalon)
regional specifications of developing brain - five primary vesicles - parts (arises from)
- Telencephalon (forebrain)
- Diencephalon (forebrain)
- Mesencephalon (Midbrain)
- Metencephalon (Hindbrain)
- Myelencephalon (Hindbrain)
regional specifications of developing brain - forebrain (prosencephalon) gives rise to
- Telencephalon
2. Diencephalon
regional specifications of developing brain - Midbrain (mesencephalon) gives rise to
Mesencephalon
regional specifications of developing brain - Hindbrain (rhomboencephalon) gives rise to
- Metencephalon
2. Myelencephalon
telencephalon - adults derivatives (wall and cavity)
wall: cerebral hemisphere
cavity: lateral ventricles
diencephalon - adults derivatives (wall and cavity)
wall: thalamus + hypothalamus
cavity: third ventricle
mesencephalon - adults derivatives (wall and cavity)
wall: midbrain
cavity: aqueduct
metencephalon - adults derivatives (wall and cavity)
wall: pons and cerebellum
cavity: upper part of fourth ventrivle
myelencephalon - adults derivatives (wall and cavity)
wall: medulla
cavity: lower part of fourth ventricle
neuroectoderm give rise to … (cells)
- CNS neurons
- ependymal cell
- oligodendroglia
- astrocytes
neural crest give rise to … (cells)
- PNS neurons
2. Schwann cells
mesoderm give rise to … (cells)
microglia
neural tube defects - mechanism
Nuropores fail to fuse (4th week) –> persistent connection between amnionic cavity and spinal canal
neuropoles fuse (when)
4th week
causes of neural tube defects
low folic acid intake before conception and during pregnancy
neural tube defects - labs
- increased a-fetoprotein (AFP) in amniotic fluid and maternal serum (except spina bifida occulta)
- increased acetylcholinesterase (AChE) in amniotic fluid in amniotic fluid (helpful confirmatory test)
neural tube defects - increased acetylcholinesterase (AChE) in amnionic fluid - mechanism
fetal acetylcholinesterase (AChE) in CSF transudates across defect into amniotic fluid
neural tube defects - increased in maternal blood and in amnitotic fluid
- a-fetoprotein (AFP) –> both maternal blood and amniotic fluid
- acetylcholinesterase (AChE) –> only amniotic fluid
Spina bifida occulta - mechanism
failure of spinal canal to close but no stractural herniatiion, and intact dura –> associated with tuft of hair or skin dimple at level of bony defect
Spina bifida occulta - area
usually at lower vertebral levels
Spina bifida occulta - lab
normal AFP
Spina bifida occulta - clinical appearance
it is associated with tuft of hair or skin dimple at level of bony defect
Spina bifida - types and MC
- Spina bifida occulta (MC)
- Meningocele
- Meningomyelocele
Meningocele - mechanism
meninges (BUT NOT NEURAL TISSUE) herniate through body defect
Meningomyelocele - mechanism
meninges and NEURAL TISSUE (eg. cauda equina) herniate through bony defect
Meningocele - clinical appearance
+/- skin defect (and cyst through it)
Meningomyelocele - clinical appearance
skin usually thin or absent (and cyst through it)
Anencephaly - pathophysiology
malformation of anterior neural tube –> no forebrain, open calvarium
Anencephaly - clinical and lab findings
- open calvarium
- polyhydramnios
- increased AFP
- frog like appearance of the fetus
Anencephaly - lab
increased AFP
Anencephaly - causes of polyhydramnios
no swallowing center in brain –> swallowing of amnionic fluid is impaired
causes of anencephaly
- maternal type 1 diabetes
2. low folic acid intake before conception and during pregnancy
it decreases the risk of anencephaly
maternal folate supplementation
Forebrain anomalies - types
- anencephaly
2. holoprosencephaly
holoprosencephaly - mechanism
failure of left and right hemispheres to separate during 5-6 weeks. Related to mutations in sonic hedgego signaling pathway
holoprosencephaly - failure of left and right hemispheres to separate during
5-6 weeks
holoprosencephaly - failure of left and right hemispheres to separate during 5-6 weeks. Related to mutations in
sonic hedgego signaling pathway
holoprosencephaly - moderate form
cleft lip/palate
holoprosencephaly - most severe form (and describe)
cyclopia –> only one eye, centrally placed at nose’s root are. There is a missing nose or a nose in the form of a proboscis (a tubular appendage) located above the eye.
holoprosencephaly - seen in
- Patau syndrome
2. fetal alcohol syndrome
neural tube defects - types
- Spina bifida occulta
- spina bifida (Meningocele, Meningomyelocele)
- Anencephaly
Posterior fossa malformations - types
- Chiari II
2. Dandy-Walker
Chiari II - pathophysiology
significant herniation of cerebellar tonsils and vermis through foramen magnum with aqueductal stenosis
–> hydrocephalus
Chiari II - hydrocephalus - mechanism
aqueductal stenosis –> obstruction of CSF flow commonly
Chiari II may occur in association with
- lumbosacral menigomyelocele –> paralysis below the defect
- syringomyelia
Dandy-Walker - pathophysiology
agenesis of cerebellar vermis with cystic enlargment of 4th ventricle (fills the enlarged posterior fossa)
Dandy-Walker is associated with
- noncommunicating hydrocephalus
2. spina bifida
syringomyelia - definition
cystic cavity within spinal cord (cystic degeneration of spinal cord)
syringomyelia is associated with …
- Chiari malformations
- trauma
- tumors
syringomyelia - MC area in the spinal cord
C8-T1
syringomyelia - pathogenesis of symptoms
Crossing anterior spinal commissural fibers are typical damaged first
syringomyelia - result in (clinical appearance)
cape like bilateral loss of pain and temperature sensation in upper extremities (FINE TOUCH SENSATION IS PRESERVED)
Chiari I malformation - mechanism
cerebellar tonsillar ectopia >3-5 mm
Chiari I malformation - clinical appearance
congenital, usually asymptomatic in childhood, manifests with feadaches and cerebellar sympotms (as the skull and brain are growing)
Tongue development
1st and 2nd branchial arches form anterior 2/3
3rd and 4th branchial arches form posterior 1/3
Tongue development - anterior 2/3 is formed by
1st and 2nd branchial arches
nerves responsible for taste (only the names)
CN VII, IX, X (solitary nucleus)
solitary nucleus - nerves
CN VII, IX, X
nerves responsible for motor on the tongue (only the names)
CN X, XII
nerves responsible for pain on the tongue (only the names)
CN V3, IX, X
tongue - anterior 2/3 sensation
CN V3
tongue - anterior 2/3 taste
CN VII
tongue - posterior 1/3 sensation
mainly via CN IX, extreme posterior via CN X
tongue - posterior 1/3 taste
mainly via CN IX, extreme posterior via CN X
tongue - main muscles and function (and innervation)
- hyoglossus (XII) –> retracts and depress tongue
- genioglossus (XII) –> protrudes tongue
- styloglossus (XII) –> draws sides of tongue upward to create a trough for swallowing
- palatoglossus (X) –> elevates posterior tongue during swallowing
causes of anencephaly
- maternal type 1 diabetes
2. low folic acid intake before conception and during pregnancy
holoprosencephaly - clinical presentation and mutation / seen in
moderate form –> cleft lip/palate
severe form –> cyclopia
mutation: sonic hedgego signaling pathway
seen in: 1. Patau syndrome 2. fetal alcohol syndrome
Chiari II may occur in association with
- lumbosacral menigomyelocele –> paralysis below the defect
- syringomyelia