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anat 312 > lecture 1 - development of the cns > Flashcards

lecture 1 - development of the cns Flashcards

1
Q

when is the pre-embryonic period?

describe organ system development at this point.

A
  • weeks 1-2

- no distinct organ systems

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2
Q

when is the embryonic period?

describe organ system development at this point.

A
  • weeks 3-7
  • most of the body systems develop during this period (CNS, heart, arms, legs, ears, eyes, teeth, palate, external genitalia) - means its the most ! tetragenic !
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3
Q

when is the fetal period?

describe organ system development at this point.

A
  • weeks 8-38
  • continuation of development of organ systems from embryonic period (except heart, arms, legs) as the baby grows in size
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4
Q

what is fertilization? where does it most commonly ocur?

A

sperm joins egg - ampulla of uterine tubes, travles to endometrium where it implants

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5
Q

what is fusion?

A

makes zygote

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6
Q

what is cell cleavage?

A

zygote –> morula

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7
Q

what is a morula? when does it typically form?

A
  • 16 cell mass

- day 4

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8
Q

what is blastulation?

A

morula –> blastula

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9
Q

what are blastomeres?

A

divisions of genetic material

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10
Q

what is a blastula? when does it typically form?

A
  • 100 cell mass

- day 5-8

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11
Q

is blastulation before or after implantation?

A

before

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12
Q

what is occuring (in more detail) during blastulation?

A
  • embryoblast and trophoblast differentiation (simultaneously)
  • formation of blastomere cavity in the centre of the blastomere
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13
Q

the trophoblast goes on to become what?

A

the placenta

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14
Q

the embryoblast goes on to become what?

A

the fetus

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15
Q

what is the trophoblast composed of?

A

cytotrophoblasts and syncytiotrophoblasts

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16
Q

are cytotrophoblasts mono- or multi-nucleated?

A

mono

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17
Q

are syncytiotrophoblasts mono- or multi-nucleated?

A

multi

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18
Q

describe the cytotrophoblasts

A

surrounds primitive yolk sac, then embryo

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19
Q

describe the syncytiotrophoblasts

A

froms through movement, fuses with maternal sinusoids to form trophoblastic lacunae (part of blood supply to embryo)

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20
Q

what do the cytotrophoblasts connect?

A

embryo to mom via blood

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21
Q

what do the syncytiotrophoblasts connect?

A

mom to embryo

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22
Q

whar does the embryoblast develop into?

A

bilaminar disc

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23
Q

describe the development of the embryoblast into the bilaminar disc

A
  • starts at day 9
  • day 12: embryoblast splits into:
  • – epiblast (surrounds amniotic cavity – embryo proper)
  • – hypoblast (surrounds exocoelomic cavity – yolk sac/allantois)
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24
Q

what is gastrulation?

A

blastula –> gastrula

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25
Q

what is a grastrula?

A

multilayered and multidemensional cell structure

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26
Q

what does gastrulation establish? what does this mean

A
  • the cranio-caudal axis

- first time we have direction in the fetus

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27
Q

where does gastrulation occur?

A

at the bilaminar disc

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28
Q

what marks the begining of gastrulation?

A

the primitive streak

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29
Q

describe gastrulation

A
  • as the primitive streak advances, the primitive node forms, which eventually turns into the primitive pit
  • along the primitive streak, the epiblast begins to undergo ingression through the primitive pit
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30
Q

During ingression, invaginating cells have four destinations - what are they?
(i.e., what is formed during gastrulation?)

A
  1. ectoderm
  2. mesoderm
  3. endoderm
  4. notocord
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31
Q

where do invaginating cells for the ectoderm end up?

A

remain in epiblast

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32
Q

what will the ectoderm become?

A

NS, epidermis, hair, nails, teeth, and sensory epithelium of eyes/ears/nose

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33
Q

where do invaginating cells for the mesoderm end up?

A

between the former hypoblast and the epiblast

34
Q

what will the mesoderm become?

A

muscles, bone, cartillage blood, bvs, notocord

35
Q

where do invaginating cells for the endoderm end up?

A

replacing the hypoblast

36
Q

what will the endoderm become?

A

lining of GI and respiratory tracts, accessory digestive organs, urinary organs, endocrine glands

37
Q

describe the notocord as a destination of invaginating cells

A
  • some ascend to oropharyngeal membrane
  • most form fetal primitive backbone (for structural integrity), which eventually develops into the nucleus pulposus (which is gelatenous tissue btween the discs in the adult back)
38
Q

neurulation spans which days of development?

A

~19-28

39
Q

describe day 19 of neurulation

A
  • epiblast begins to thicken cranially, forming the neural plates
  • lateral edges of the neural plates elevate, while the midline depresses
40
Q

describe day 20 of neurulation

A
  • neural fold begins to fold dorsally in the middle of the craniocaudal axis forming the neural groove
  • folding proceeds both cranially and caudally
41
Q

describe day 22 of neurulation

A
  • neural tube begins to close at the middle

- fusion proceeds both cranially and caudally

42
Q

describe day 23 of neurulation

A

neuropores begin to close (last part)

43
Q

when does the cranial neuropore close?

A

day 26

44
Q

when does the caudal neuropore close?

A

day 28

45
Q

what happens when the neuropores fail to close?

A

neural tube defect

46
Q

what (specifically) results when the cranial neuropore fails to close?

A

anencephaly - born without sections of the frontal lobe, cerebrum, and skull (because it develops around the developing brain)

47
Q

what (specifically) results when the caudal neuropore fails to close?

A

spina bifida - neural tube doesn’t close all the way in the spinal cord - bulges out - can cause movement problems

48
Q

what are neural crest cells?

A

during neural folding, cells from the neural folds break off and migrate to form other structures

49
Q

what do neural crest cells become?

A
  • dorsal root ganglia
  • autonomic chain ganglia
  • adrenal medulla
  • schwann cells of PNS
  • melanocytes
  • dermis, sm and adipose of the face
50
Q

breify decsribe the development of the sc

A

neuroepithelium divides into neuroblasts (primitive nerve cells), forming:
( 1) deep mantle layer (gray matter) (neural tube itself)
(2) superficial merginal layer (white matter)

51
Q

the deep mantla layer can be further subdivided into:

A 
alar plate (sensory, dorsal)
basal plate (motor, ventral)
sulcus limitans
52
Q

what distinguishes the alar and basal plate?

A

sulcus limitans

53
Q

the neural tube dilates to form 3 primary vesicles:

A

prosencephalon (forebrain)
mesencephalon (midbrain)
rhombencephalon (hindbrain)

54
Q

what are the secondary vesicles of the prosencephalon?

A

telecephalon, diencephalon

55
Q

what does the telecephalon form?

A

cerebrum

56
Q

what does the diencephalon form?

A

thalamus and hypothalamus

57
Q

what are the secondary vesicles of the mesencephalon )?

A

mesecephalon

58
Q

what does the mesencephalon form?

A

midbrain

59
Q

wheat are the secondary vesicles of the rhombencephalon?

A

metencephalon, myelencephalon

60
Q

what does the metecephalon form?

A

pons and cerebellum

61
Q

what does the myelencephalon form?

A

medulla oblongata

62
Q

which secondary vesicle forms the lateral ventricles?

A

telencephalon

63
Q

which secondary vesicle forms the third ventricle?

A

diencephalon

64
Q

which secondary vesicle forms the cerebral aqueduct?

A

mesencephalon

65
Q

which secondary vesicle forms the fourth ventricle?

A

rhombencephalon

66
Q

which secondary vesicle forms the central canal?

A

mesencephalon

67
Q

what are the 3 spinal flexures?

A

cephalic, cervical and pontine

68
Q

where is the cephalic flexure?

A

exists entirely in the mesencephalin

69
Q

where is the cervical flexure?

A

exists at the end of the vesicles - distinguishes the brain and spinal cord

70
Q

where is the pontine flexure?

A

distinguishes metencephalon and myelencephalon

71
Q

what is the first flexure to form?

A

cephalic

72
Q

what is the last flexure to form?

A

pontine

73
Q

describe the ‘C-shape’

A
  • neurons in the neocortex (telencephalon) proliferate, migrate and begin to devlop connections rapidly
  • causes C-shape rotation because the skull cannot contain all of these new connections
74
Q

what signals the end of fertilization?

A

implantation (development of fibrin coagulum)

75
Q

what is the result of increased cortical convolutions?

A

(gyri and sulci) - increased surface area

76
Q

summarize the events of week 1

A
  • fertilization
  • cleavage
  • implantation begins
77
Q

summarize the events of week 2

A
  • embryoblast differentiation
  • trophoblast differentiation
  • implantation is complete - fibrin coagulum
78
Q

summarize the events of week 3

A

ingression (ectoderm, mesoderm, endoderm, notocord)

79
Q

when does the embryo become asymetric?

A

week 3

80
Q

summarize the events of week 4

A

neurulation

81
Q

when, specifically, does brain development occur?

A

end of the 1st trimester

anat 312 (18 decks)

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