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Embryology > T12- CNS Development > Flashcards

T12- CNS Development Flashcards

1
Q

What happens during primary neurlation

A

The primary neural tube forms from the neuroectoderm of the neural plate

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2
Q

What happens during secondary neurulation

A

The secondary neural tube forms from mesodermal remains of the primative streak

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3
Q

What are the steps of primary neurlation

A
  1. Induction of neuroectoderm 2. Elevation of the neural folds 3. Conversion, contact, and fusion of the neural folds 4. Differentiation of surface ectoderm
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4
Q

In elevation of the neural folds, (a) what is created? and (b) what importance does the notocord have?

A

(a) A distinct shape is created with the aid of cell wedging at the median hinge point (b) the notochord controls the position of the median hinge point

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5
Q

When does first fusion of the neural folds occur?

A

at the 5th somite pair

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6
Q

In which direction does fusion occur

A

at a cranial+caudal direction

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7
Q

Prior to neuropore closure, the _____________ is in open communication with the ____________ at both cranial and caudal ends

A

neural canal; amniotic cavity

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8
Q

Remanining mesenchymal cells of the ____________ occupy a midline position within the____________

A

primative streak, caudal eminence (tail bud)

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9
Q

Where are primative streak mesenchymal cells located in reference to the neuropore

A

they’re located caudally to the neuropore

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10
Q

What does primative streak mesenchyme condense into during secondary nerulation

A

the medullary cord

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11
Q

Steps of secondary neurlation

A
  1. Formation of medullary cord 2. Mesenchymal cells transition into epithelial cells 3. Canalization of epithelial cells 4. Joining of lumen of medullary cord and neural canal
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12
Q

What are neuroepithelial cells

A

tall columnar cells found in the ventricular zone of the neural tube

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13
Q

What does rapid proliferation of the neural tube cause?

A

(a) A psuedostratified appearance on the ventricular zone (b) An overall thickening of the NT wall (c) Change in shape and size of the neural canal

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14
Q

Newly formed neuroepithelial cells differentiate into what

A

neuroblasts+glioblasts

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15
Q

Where do neuroblasts and glioblasts migrate into

A

the intermediate zone

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16
Q

Neuroepithelial cells that remain in the ventricular zone transition into what

A

ependymal cells

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17
Q

Where does the spinal cord begin to develop

A

from the neural tube caudal to the 4th pair of somites

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18
Q

Neural tube that forms the spinal cord was created by both ___________ and _________ neurulation

A

primary; secondary

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19
Q

Where does sonic hedgehog influence neuroepithelial cells

A

in the ventral half of spinal grey matter

20
Q

What are bone morphogenic protiens (a) produced by? and (b) what do they influence

A

(a) produced by adjacent ectoderm (b) influence neuroepithelial cells in the dorsal half of spinal grey matter

21
Q

What does the ventral half of spinal grey matter become?

A

the basal plate

22
Q

What is the basal plate associated with?

A

motor neurons

23
Q

What does the dorsal half of spinal grey matter become?

A

the alar plate

24
Q

What is the alar plate associated with?

A

sensory neurons

25
Q

With differentiation of the spinal grey matter, what happens to the neural canal?

A

The neural canal begins to shrink in size

26
Q

What does the ventricular zone become?

A

ependymal cells which line the neural canal

27
Q

What does the intermediate zone become?

A

grey matter (nerve cell bodies)

28
Q

What does the marginal zone become?

A

white matter (nerve cell axons)

29
Q

Where is the midline roof plate located?

A

dorsally

30
Q

Where is the floor plate located?

A

ventrally

31
Q

The midline roof plate and floor plate do not contain __________ and instead serve as pathways for _____________

A

neuroblasts; crossing fibers

32
Q

The notochord, which is responsible for secreting ____________ determines where it has the most influence

A

sonic hedgehog

33
Q

What happens if there is no notochord

A

no motor neurons form

34
Q

What happens if the notochord is transplanted

A

there would be a formation of an ectopic floor plate with associated motor neurons

35
Q

How is the spinal cord in the early embryo

A

it extends the entire length of the vertebral cord and all SC nerve segments lie adjacent to corresponding vertebral segments

36
Q

What happens in the growing fetus concerning vertebral elongation?

A

vertebral column elongation occurs faster than that of the SC

37
Q

Where does the brain begin to develop?

A

from the neural tube, cranial to the 4th pair of somites

38
Q

Brain developent is derived from ___________ nerulation only

A

primary

39
Q

Closure of the _______ neuropore forms three ________ brain vessicles

A

cranial; primary

40
Q

What is the cervical flexure

A

the point of transition of the spinal cord and the rhombencephalon

41
Q

Where is the midbrain flexure located?

A

in the middle of the mesencephalon

42
Q

What are the three primary brain vessicles

A

proencephalon, mesencephalon, rhombencephalon

43
Q

When does transition of primary vessicles to secondary vessicles occur

A

in the 5th week

44
Q

Histogenesis of the brain What happens to ependymal cells that migrate to the intermediate zone

A

They form deep grey matter structures near the ventricles

45
Q

Histogenesis of the brain What happens to ependymal cells that migrate to the marginal zone

A

They form the grey matter surounding the white matter in the brain

46
Q
A

(a) Telencephalon
(b) Diencephalon
(c) Lateral Ventricles
(d) Thalami
(e) Midbrain
(f) Cerebral Aqueduct
(g) Pons
(h) Cerebellum
(i) Lower part of the 4th ventricle

Embryology (14 decks)

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