Neurology- Embryo Flashcards
What induces the overlying ectoderm to differentiate into neuroectoderm and to form the neural plate?
Notochord
What does the neural plate give rise to?
the neural tube and neural crest cells
What does the notochord become?
the nucleus pulposus of intervertebral discs in adults
When does neural crest development occur?
days 18-21
What are the three primary developmental vesicles of the brain?
- forebrain (prosencephalon)
- midbrain (mesencephalon)
- hindbrain (rhombencephalon)
What are the secondary vesicle derivatives of the forebrain?
telencephalon and diencephalon
What are the adult derivatives of the telencephalon?
cerebral hemispheres and lateral ventricles
What are the adult derivatives of the diencephalon?
thalamus and 3rd ventricle
What are the secondary vesicle derivatives of the midbrain?
the mesencephalon
What are the adult derivatives of the mesencephalon?
midbrain and aqueduct
What are the secondary vesicle derivatives of the hindbrain?
metencephalon and myelencephalon
What are the adult derivatives of the metencephalon?
pons, cerebellum
upper part of 4th ventricle
What are the adult derivatives of the myelencephalon?
medulla and lower part of the 4th ventricle
What are the CNS/PNS derivatives of the neuroectoderm?
CNS neurons, ependymal cells (inner lining of ventricles, make CSF), oligodenroglia, astrocytes
What are the CNS/PNS derivatives of the neural crest?
PNS neurons, Schwann cells
What are the CNS/PNS derivatives of the mesoderm?
microglia
What neural tube defect can cause a persistent conenction between the amniotic cavity and the spinal canal? What is the cause?
failure of neuropores to fuse in the 4th week
This is associated with low folic acid intake before conception and during pregnancy
What lab findings are seen in neural tube defects?
elevated a-fetoprotein in amniotic fluid and maternal serum
elevated AchE in amniotic fuid to confirm (fetal AchE in the CSF transudates across the defect into amniotic fluid)
What are some common neural tube defects?
- spina bifide occulta
- meningocele
- meningomyelocele
What is spina bifida occulta?
failure of the bony spinal canal to close, but with no structural herniation (dura is intact). Usually seen at the lower vertebral levels
Spina bifida occulta- AFP is normal
See FA pg 449
What is the difference between meningocele and meningomyelocele?
meningocele - meninges (but no neural tissue) herniate through the bony defect
meningomyelocele- meninges and neural tissue herniate
What are two common forebrain anomalies?
anencephaly
holoprosencephaly
What is anencephaly?
malformation of the anterior meural tube resulting in no forebrain, and an open calvarium
What is holoprosencephaly?
failure of the left and right hemospheres to seperate
When does holoprosencephaly typically occur?
5-6 weeks
What typically causes holoprosencephaly?
mutations in the sonic hedgehod signaling pathway
Holoprosencephaly is commonly seen in what syndromes?
Patau syndrome and fetal alcohol syndrome (moderate form has a cleft lip/palate and the most severe form results in cyclopia)
How does anencephaly present in labs?
elevated AFp and polyhydramnios (no swallowing center in the brain)
Anencephaly is associated with ________
maternal type I diabetes
What is a Chiari II malformation?
significant hernation of the cerebellar tonsils and vermis through the foramen magnum with aqueductal stensosi and hydrocephalus
What is a Dandy-Walker malformation?
agenesis of cerebellar vermis with cystic enlargement of the 4th ventricles (which fills the enlarged posterior fossa)
associated with hydrocephalus and spina bifida
What is syringomyelia?
the formation of a cystic cavity within the spinal cord that results in a cape-like, bilateral loss of pain and temperature sensation in the upper extremities (fine touch is preserved)
Syringomyelia is most common at what vertebral levels?
C8-T1
What is a Chiari I malformation?
cerebellar tonsillar ectopia greater than 3-5mm; congential, usually asymptomatic in childhood and manifesting with HA and cerebellar symptoms
What forms the anterior 2/3rds of the tongue?
1st and 2nd branchial arches
Sensation to the anterior 2/3rds of the tongue is via ____
CN V3
Taste to the anterior 2/3rds of the tongue is via ____
CN VII
What forms the posterior 1/3rd of the tongue?
the 3rd and 4th branchial arches
Sensation and taste to the posterior 1/3rd of the tongue is via what?
CN IX (extreme back is CN X)
Motor innervation of the tongue
via CN XII to hyoglossus (retracts and depresses the tongue), genioglossus (protrudes the tongue), and styloglossus (draws sides of tongue upward to create a trough for swallowing)
via CN X to palatoglossus (elevates posterior tongue during swallowing)
