Embryo

Question 1

what are 2 mechs. creating a neural tube

Answer 1

1. primary neurulation - primary neurla tube from neuroectoderm and nerual plate
2. secondary neurolation - secondary tube from mesoderm left from primitive stalk

Question 2

what are 2 main steps to primary neurulation

Answer 2

1. induction of neuroectoderm from neural plate

2. elevation apposition, contact and fusion of the folds

Question 3

what organizes neuroectoderm

Answer 3

notochord

Question 4

where does closure begin

Answer 4

in what will be cervical and goes rostral and caudal

Question 5

what are ends where fusion occurs called

Answer 5

rostral and caudal neuropores

Question 6

what happens at the caudal end of neural closure

Answer 6

medullary cord condense and tube extends into it and undergoes mesenchymal condensation

Question 7

what does this caudal neurulation form?

Answer 7

the sacrum

Question 8

what is freq. of neural tube defects

Answer 8

1:1000

Question 9

what are risk factors for defects

Answer 9

Hx of defects, diabetes, obesisty, anticonvulsant meds — most women have none

Question 10

what lowers risk

Answer 10

folic acid

Question 11

what is unclosed rostral pore

Answer 11

anencephaly

Question 12

what is arnold chiari malformation

Answer 12

posterior cransial fossa too small and foramen of mygandi compressed to get hydrocephalus

Question 13

what are 2 ultrasound signs of spina bifida

Answer 13

lemon sign - flattening of frontal bone

banana sign - curved contour of cerebellum

Question 14

what are 2 steps of shaping the neural tube

Answer 14

1. dev. of brain vesicles

2. dev. of brain flexures

Question 15

what are primary vesicles (3)

Answer 15

1. proencephalon
2. mesencephalon
3. rhombencephalon

Question 16

what are secondary vesicles and what will they become (5)

Answer 16

1. telencephalon - hemispheres
2. diencephalon
3. mesencephalon - midbrain
4. metencephalon - pons and cerebellum
5. myencephalon - medulla

Question 17

what are the 3 flexures

Answer 17

1. midbrain flexure
2. cervical flexure
3. pontine flexure

Question 18

what forms intermediate zone

Answer 18

migration of neurobalst and glioblasts toward outer wall (will be grey matter)

Question 19

what forms marginal zone

Answer 19

extension of neuroblasts even further out (will form white matter)

Question 20

what happens to cells that remain adjacent to neural tube

Answer 20

ependymal cells

Question 21

what are layers of tube from in to out

Answer 21

ventricular>intermediate>marginal

Question 22

how is grey matter established in cortex

Answer 22

radial glial cells extend out into margins and primitive neuroblasts migrate along them

Question 23

what are dorsal and ventral thickening of intermediate zones

Answer 23

1. dorsal - alar plates

2. ventral - basal plates

Question 24

what do these plates become

Answer 24

1. alar plates - interneurons

2. basal plates - motor neurons

Question 25

what signalling proteins are used to differentiate floor from roof

Answer 25

floor releases SHH - basal plates

roof releases BMP -alar plates

Question 26

what causes the outward flaring of alar plates at the medulla and pons

Answer 26

the pontine flexure

Question 27

what are 2 consequences of the faster growth of the vert than the cord

Answer 27

1. dissociation of the cord from vert. segments

2. cauda equina

Question 28

what 2 things is PNS developed from

Answer 28

1. neural tube

2. neural crest

Question 29

what does the tube contribute to

Answer 29

1. lower motor neurons

2. preganglionic autonomic neurons

Question 30

what do the crest cells become

Answer 30

1. dorsal root ganglia

2. post-ganglionic neurons of autonomic system