Neuroembryology SDL

Question 1

this forms the notochord

Answer 1

midline axial mesoderm

Question 2

the notochord induces the overlying ectoderm to form the____

Answer 2

neural plate

Question 3

ectoderm germ layer

Answer 3

neural tube & neural crest derivatives; CNS, PNS, sensory epithelium of nose, eye and ear, pituitary gland, mammary glands, epidermis, hair, nails, sweat glands, enamel of teeth, some eye mm

Question 4

mesoderm germ layer

Answer 4

dura mater and connective tissue envestments of peripheral nerves

Question 5

endoderm germ layer

Answer 5

parenchyma of the tonsils, thyroid, parathyroid, thymus

Question 6

lumen of the notochordal canal transiently connects the amniotic cavity with the yolk sac to form the _____

Answer 6

neuroenteric canal

Question 7

cells in the neural plate constitute the

Answer 7

neuroectoderm

Question 8

separation of the neural tube from the surface ectoderm

Answer 8

dysjunction

Question 9

these cells undergo an epithelial-mesenchymal transition and migrate away from the neuroectoderm to enter adjacent embryonic mesoderm

Answer 9

neural crest cell

Question 10

neural crest cell derivatives

Answer 10

Schwann cells & glial cells of PNS; DRG; spinal & cranial nerve ganglia; leptomeninges (pia & arachnoid); ANS (simp & parasymp postgang); mesenchyme of pharyngeal arches (connective tissue/bones of the face and skull, dermis of face/neck, thyroid C cells, conotruncal septal heart cells); adrenal medulla cells; pigment cells (melanocytes)

Question 11

completion of this marks the end of primary neurulation

Answer 11

ectoderm fusion (at ends of neural tube); anterior neuropore @ day 25 & posterior @ day 27

Question 12

coalescence of caudal mass mesenchymal

cells into a rod followed by cavitation to form a tube & fusion with primary neural tube

Answer 12

secondary neurulation

Question 13

levels involved in primary & secondary neurulation

Answer 13

C1-S2 & S3-Co (or C1-S1 & S2-Co)

Question 14

folic acid in pregnancy: how much, when why?

Answer 14

400 ug/day; 2 months prior to conception; 70% reduction in NTDs

Question 15

spina bifida occulta typically occurs in this region & is what type of neurulation defect

Answer 15

lower lumbar/upper sacral; secondary neurulation defect

Question 16

failure of the secondarily formed neural tube to join the neural tube formed from primary neurulation & exs of this

Answer 16

secondary neurulation defect; spina bifida occulta, tethered spinal cord, caudal regression syndrome, diastematomyelia

Question 17

an absence of lamina and spines that occurs in the upper regions of the vertebral column arise from what & cause what condition

Answer 17

arise from incomplete fusion of posterior neuropore during primary neurulation; cause spina bifida occulta

Question 18

total failure of neurulation, no dysjunction; can occur in spinal cord or brain region; most severe NTD

Answer 18

rachischisis; craniorachischisis

Question 19

failure to close anterior neuropore at cranial end of neural tube by day 25 during primary neurulation (C1-S2 level); most of brain doesn’t develop as a result

Answer 19

anencephaly

Question 20

failure of posterior neuropore closure (neural plate caudal to neck is open)

Answer 20

myeloschisis

Question 21

defect in vertebral arches covered by skin & usually doesn’t involve underlying neural tissue; failure to close posterior neuropore on day 27 at caudal end of neural tube during primary neurulation (C1-S2 level but most common at S1-S2); Failure of sclerotome cells to migrate into the region dorsal to the neural tube leading to the absence of vertebral arches in that region

Answer 21

spina bifida occulta

Question 22

defect with protrusion of meninges or neural tissue

Answer 22

spina bifida cystica

Question 23

a fluid-filled sac of meninges protrudes through the defect

Answer 23

meningocele

Question 24

partial failure of posterior neuropore closure; neural tissue & meninges included in the fluid-filled sac protruding through the defect; most severe spina bifida NTD & occurs by day 27

Answer 24

myelomeningocele

Question 25

anterior neuropore defect where brain & meninges protrude through opening in skull; partial failure occurs by day 25

Answer 25

encephalocele

Question 26

persistence of neurenteric canal causes split spinal cord; a secondary neurulation prob

Answer 26

Diastematomyelia

Question 27

caudal end of cord fixed by fibrous bands; lipomas (fat pads) often associated w this; a secondary neurulation prob

Answer 27

Tethered spinal cord

Question 28

sacral hypoplasia/hypolastic femors (caudal dysgenesis); a secondary neurulation prob

Answer 28

Caudal regression syndrome

Question 29

ventral induction defect; failure to form 2 cerebral hemispheres; fails to cleave & remains fused as single midline entity; alcohol & maternal diabetes may be risk factors; shh may be involved; occurs in wks 5-6

Answer 29

holoprosencephaly

Question 30

cleft brain; disorder of migration in month 3-5

Answer 30

schizencephaly

Question 31

smooth brain ( few gyri); disorder of migration in month 3-5

Answer 31

lissencephaly

Question 32

broad gyri (too few gyri); disorder of migration in month 3-5

Answer 32

pachygyri

Question 33

small gyri (too many gyri); disorder of migration in month 3-5

Answer 33

polygyri

Question 34

Persistence of the neuroenteric canal leads to adhesions that can cause what developmental anomalies?

Answer 34

tethered spinal cord, malrotation of gut, neuroenteric fistula, dorsal dermal sinus tracts/cysts, split spinal tract

Question 35

this is formed from the lumen of the notochordal canal to connect the amniotic cavity w the yolk sac

Answer 35

neural enteric canal

Question 36

what secretes GFs in primary neurulation?

Answer 36

notochord

Question 37

neural crest cells give rise to what of the PNS?

Answer 37

DRG & Schwann cells, meninges, sympathetic neuroblasts, mesenchyme of pharyngeal arches

Question 38

NTD risk factors

Answer 38

- Folic acid deficiency (alcoholics, nutritional deficiency) - Diabetic mothers - Antiepileptic drugs - Previous pregnancy with NTDs - Hyperthermia (hot tubs)

Question 39

which protein would increase in maternal serum and amniotic fluid in cases of a neural tube defect?

Answer 39

alphafetoprotein

Question 40

what induces overlying ectoderm to differentiate into neuroectoderm?

Answer 40

Shh

Question 41

what promotes dorsoventral differentiation of the spinal cord?

Answer 41

opposing Shh & BMP concentration gradients

Question 42

what is formed by the alar plate under influence of BMPs?

Answer 42

dorsal (sensory) spinal cord

Question 43

what is formed by the basal plate under the influence of Shh?

Answer 43

ventral (motor) spinal cord

Question 44

which cells give rise to neuroblasts in the developing spinal cord?

Answer 44

neuroepithelial cells in wall of neural tube

Question 45

which cells give rise to the astrocytes and oligodendroglia?

Answer 45

gliablasts (pseudostratified layer of neuroepithelial cells in wall of neural tube )

Question 46

what is the function of the radial glia in the developing cerebral cortex?

Answer 46

function as scaffolds for neuronal migration & then become astrocytes

Question 47

underlying cause of schizencephaly, lissencephaly, pachygyri or polygyri?

Answer 47

disruption of fetal neuronal migration due to various reasons

Question 48

spatial and temporal differences in what genes are important for anterior-posterior axis development, neural tube segmenting, and secondary neurulation?

Answer 48

homeobox genes

Question 49

imp for ventral induction

Answer 49

Shh

Question 50

Why does maturation of spinal cord proceed in a rostral-caudal direction?

Answer 50

FGF secreted in gradient (low rostrally, high caudally) that maintains immaturity of caudal neural progenitor cells

Question 51

This pseudostratified layer gives rise to neurons, astrocytes, oligodendrocytes, & then ependymal cells

Answer 51

neuroepithelial cells in wall of neural tube

Question 52

What form the mantle layer surrounding the neural tube, “gray matter of the spinal cord”

Answer 52

neuroblasts

Question 53

This layer surrounds the neural tube and contains nerve fibers from the neuroblasts in the mantle layer; forms the outmost layer of spinal cord

Answer 53

marginal layer

Question 54

Thickening of this layer dorsally forms the alar plate & basal plate

Answer 54

mantle layer

Question 55

the alar plate is

Answer 55

dorsal horn-sensory

Question 56

the basal plate is

Answer 56

ventral horn-motor

Question 57

These primitive nerve cells form a zone around the neuroepithelial layer called the mantle layer, which later forms the gray matter of the spinal cord

Answer 57

neuroblasts

Question 58

imp for dorsal induction

Answer 58

BMP

Question 59

derived from vascular mesenchyme (mesoderm) when blood vessel grow into nervous system

Answer 59

microglial cells

Question 60

derived from neuroepithelial cells after neuroblasts forms

Answer 60

glial cells 1. mantle layer-astrocytes 2. marginal layer-oligodendrocytes

Question 61

when neuroepithelial cells cease to produce neuroblasts & gliablasts they differentiate into this cell type which lines the central canal of spinal cord

Answer 61

ependymal cells

Question 62

these form sensory ganglia (DRG), sympathetic neuroblasts, Schwann cells, pigment cells, odontoblasts, meninges, and mesenchyme of the pharyngeal arches

Answer 62

neural crest cells

Question 63

herniation of part of cerebellum into foramen magnum is called what & can obstruct the flow of CSF & cause this condition

Answer 63

Arnold-Chiari; hydrocephaly