Neural embryology Flashcards
when is neural development (when the notochord and neural plate develop)
Day 18 to Day 21
what do the walls and cavity of the prosencephalon become (what are the intermediate secondary vesicles)
prosencephalon becomes telencephalon and diencephalon; telencephalon becomes the cerebrum (walls) and lateral ventricles (cavity); diencephalon becomes the thalamus (walls) and 3rd ventricle (cavity)
what does the mesencephalon become (adult derivatives of walls and cavity)
midbrain (walls) and cerebral acqueduct (cavity)
what does the hindbrain (rhombencepalon) become (secondary intermediates and adult derivatives of walls and cavities)
metencephalon and myelencephalon;
metencephalon becomes pons and cerebellum (walls) and upper half of 4th ventricle
myelencephalon becomes the medulla and lower half of 4th ventricle
what germ cell layer do microglia originate from
mesoderm
what cells of the nervous system originate from the neural crest cells
PNS neurons and Schwann cells
what cells of the nervous system originate from the neuroectoderm
CNS neurons, oligodendrocytes, astrocytes, ependymal cells
what lab abnormalities indicate a neural tube defect; how is diagnosis confirmed
increased AFP in amnionic fluid and maternal serum, increased AChE in amnionic fluid (confirms diagnosis)
what increases risk of neural tube defects
folate deficiency around conception and pregnancy
describe the anatomic defect of spina bifida occulta
bony spinal canal doesn’t close all the way; no spinal cord herniation; dura intact; tuft of hair or skin dimple can be seen at the level of the defect
what’s the difference between meningocele and meningomyelocele
in meningocele the spinal canal is open and only the meninges herniate whereas in meningomyelocele the spinal cord also herniates out
what early developmental abnormality leads to anencephaly
failure of the forebrain to develop leads to no cerebrum, an open calvarium and polyhydramnios because swallowing centers are missing
what are two risk factors for anencephaly
diabetes mellitus type I and folate deficiency
what developmental abnormality leads to eventual holoprosencephaly and what is the clinical presentation
failure of the cerebrum to separate into two lateral hemispheres (during week 5-6); newborns can have cleft lip/palate and, in severe cases, cyclopia
what genetic abnormality leads to holoprosencephaly
sonic hedgehog mutations can lead to holoprosencephaly
what is a Chiari II (Arnold Chiari malformation) and what is the likely cause
herniation of the cerebellar tonsils and vermis through the foramen magnum; likely due to aqueductal stenosis and hydrocephalus
what other CNS condition does Chiari II present with (besides aqueductal stenosis and hydrocephalus)
Chiari II is often seen with lumbosacral meningomyelocele (paralysis below this point)
describe Dandy-Walker malformation
an enlarged fourth ventricle leads to agenesis of the vermis
what two conditions are associated with Dandy-Walker malformations
hydrocephalus and spina bifida
what is syringomelia and what nerve fibers does it usually impact first
syringomelia is a condition in which there is a cystic cavity in the spinal cord; nerve fibers passing through the anterior commissure are usually impacted first leading to cape-like distribution of pain and temperature deficits in the upper extremity
what is the most common site for syringomelia
C8 - T1
what developmental abnormality is syringomelia associated with
Chiari I malformation (ectopia, aka displacement, of the cerebellar tonsils)
what symptoms are usually seen in Chiari I malformation
usually asymptomatic in childhood and manifests with headaches and cerebellar deficits
what progenitor structure forms the innervation of the anterior 2/3 of the tongue
1st and 2nd brachial arches form anterior 2/3 of the tongue
what progenitor structure forms the innervation of the posterior 1/3 of the tongue
3rd and 4th brachial arches form the posterior 1/3 of the tongue
what progenitor structure forms the muscles of the tongue
occipital myotome
