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Flashcards in Embryology Deck (36):
1

What does neural plate do?

notochord influences neuroectoderm to become neural plate --> neural folds --> neural groove --> neural tube and neural crest cells

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prosencephalon

forebrain

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mesencephalon

midbrain

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rhombencephalon

hindbrain

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neural tube -->

brain and spinal cord (split by 4th pair of somites)

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neural crest cells -->

Peripheral Nervous System + many non-neural derivatives

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Neural canal -->

ventricles of brain, central canal of spinal cord

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cell layers in neural tube

ventricular, intermediate, marginal

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ventricular layer of neural tube -->

wall of neural tube thickens, differentiate into neuroblasts (neurons) and glioblasts (glial cells), then becomes ependyma

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Intermediate layer of neural tube -->

becomes populated by neuroblasts formed in ventricular layer --> gray matter of spinal cord = cell bodies

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Marginal layer of neural tube -->

includes axons of neuroblasts whose cell bodies are in intermediate layer and ganglia --> white matter

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mitotic ability of neural cells

neurons - non-mitotic
glial cells - mitotic

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neurons of sensory ganglia derived from

neural crest cells

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motor neurons in ventral horn derived from

basal plate (neural tube --> intermediate layer --> basal plate)

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sensory neurons in dorsal horn derived from

alar plate (neural tube --> intermediate layer --> alar plate)

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spinal taps where

below L3 (L4-L5?)

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forebrain -->

telencephalon (cerebral hemispheres)
diencephalon (thalamus, etc.)

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midbrain -->

midbrain

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hindbrain -->

metencephalon --> pons and cerebellum
myelencephalon --> medulla

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ventricles associated with what parts of brain

lateral - cerebral hemispheres
third - diencephalon
cerebral aqueduct - mesencephalon
fourth - rhomencephalon

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optic nerve and retina form from

outgrowth of diencephalon

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pituitary gland from

dual:

infundibulum from neuroectoderm (diencephalon)
rathke's pouch - outgrowth of ectoderm (oral --> gland)

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olfactory tract grows from

telencephalon

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cranial nerve nuclei location

CN I -- telencephalon (outgrowth)
CN II -- diencephalon (outgrowth)
CN III, IV -- mesencephalon (midbrain)
CN V -XII -- metencephalon and myelencephalon

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congenital megacolon (Hirschsprung's disease)

neural crest cells fail to migrate into colon - parasympathetic ganglia do not form

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waardenburg syndrome

diffuse disruption of migration of neural crest cells
1) abnormal appearance of face, deafness, due to head neural crest cell involvement
2) lack of pigmentation (melanocytes)
3) digestive problems (enteric ganglia)

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defective closure of neural tube during weeks 3 and 4 of gestation resulting in major malformations of the CNS

neural tube defects

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craniorachischisis

complete failure of neural tube to close resulting in exposure of malformed tissue to outside of head and body

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failure of rostral neural tube to close -->

Anencephaly or Meroanencephaly
encephalocele

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failure of caudal neural tube to close -->

spina bifida (occulta, cystica) or occult spinal dysraphism

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NTDs detected in utero with

AFP and acetylcholinesterase in amniotic fluid, maternal blood

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failure of normal development of forebrain - not divided into two hemispheres

holoprosencephaly

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Tubular cavitation of the spinal cord -- generally cervical/upper thoracic
Pathogenesis unknown; probably diverse
Neural deficits begin with loss of pain & temperature sensation over shoulders and upper arms.
Often associated with Type I chiari

syringomyelia

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Dilation of the ventricles
Due to CSF overproduction, obstruction of flow or failure of CSF reabsorption

hydrocephalus

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Partial or complete absence of cerebellar vermis

dandy-walker malformations

36

Arnold-Chiari malformation

Type 1: may be asymptomatic or may not be evident until 30’s or 40’s
Type 2: herniation below foramen magnum; often accompanied by myelomeningocele
Type 3: occipital encephalocele, syringomelia
Type 4: lack of cerebellar development