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Human Structure > Human Development #3 > Flashcards

Human Development #3 Flashcards

1
Q

What are the main events of the 3rd and 4th weeks of development?

A

Gastrulation and neurulation

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2
Q

Gastrulation

A

Formation of the 3 primary germ layers

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3
Q

Neurulation

A

Formation of the neural tube, which becomes the CNS

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4
Q

Which cells give rise to 3 1º germ layers?

A

Epiblasts

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5
Q

Ectoderm

A

Outer layer; derivitives= epidermis and nervous system

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6
Q

Mesoderm

A

Middle layer; derivitives= muscles, bones, organs, support tissues, etc.

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7
Q

Endoderm

A

Inner layer; derivatives =. G.I. Lining, lower res. Tract, urogenital tracts

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8
Q

Epithelial cells characteristics

A
  • Polarized
  • apical and basal surfaces
    Attached to extra cellular matrix (ecm)
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9
Q

Mesenchymal cell characteristics

A
  • Apolar in e.c.m
  • surrounded by (ecm)
  • migrate through the E.C. M
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10
Q

Epithelial to mesenchymal transformation

A

Key for pattern formation/ reorganization of cells

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11
Q

When does gastrulation begin and end?

A

Beginning in early 3rd week; resolving by end of 4th week

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12
Q

What structure directs gastrulation?

A

Primitive streak

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13
Q

What ingresses through primitive streak?

A

Epiblasts

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14
Q

First wave of epiblast ingression

A

Epiblasts replace hypoblasts to form ENDODERM; mesenchyme => endoderm

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15
Q

Second wave of epiblast ingression

A

Epiblasts fill in the middle space to form MESODERM; mesoderm does not equal mesenchyme

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16
Q

3rd wave of epiblast ingression

A

Epiblasts that do not migrate form ectoderm; epiblasts do not equal ectoderm

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17
Q

Primitive streak

A

Thickening of epiblasts; establishes cranio-caudal axis and drives cranio-caudal development

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18
Q

Which orientation are epiblasts

A

Dorsal

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19
Q

Which orientation are hypoblasts?

A

Ventral

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20
Q

At which end does the oropharyngeal membrane form?

A

Cranial

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21
Q

Where does the cloacal membrane form?

A

Caudal; caudal to primitive streak

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22
Q

Where does primitive streak form?

A

Toward caudal axis, but cranial to the cloacal membrane

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23
Q

Components of primitive streak?

A

Primitive groove, primitive node cranially

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24
Q

What process must epiblasts of the primitive groove undergo before ingression?

A

Epithelial to mesenchymal transformation followed by transformation back to epithelial after reaching destination

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25
Q

What germ layer spreads through embryoblast?

A

Mesoderm

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26
Q

What forms the notochord?

A

Midline mesoderm

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27
Q

________ migrates __________ to reach the extra embryonic mesoderm

A

Mesoderm; laterally

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28
Q

Mesoderm migrates cranially to form the __________ region

A

Cranially, cranial to oropharyngeal membrane

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29
Q

Mesoderm fills the entire trilaminardisk, except….

A

At the oropharyageal+cloacal membranes

30
Q

What components make up the tri laminar disk after gastrulation is complete?

A

Dorsal to ventral: ectoderm, mesoderm, endoderm with the notochord running through the mesoderm cranial to caudal

31
Q

What happens to the primitive streak as the notochord forms?

A

It regresses.

32
Q

What is the clinical result of failure of primitive streaksí streak regression?

A

Sacrococoygeal teratoma

33
Q

When does neurulation begin and end?

A

Begin at end of 3rd week; resolves by end of 4th week.

34
Q

What directs neurulation?

A

The notochord.

35
Q

Where is neural plate formed?

A

In midline over the notochord, from ectoderm

36
Q

How is the neural tube formed?

A

Dorsal folding of neural plate

37
Q

What occurs as the neural tube closes?

A

Neural crest cells begin migration

38
Q

Name some derivatives of neural crest cells

A

Neuralgia, PNS ganglia, chromaffin cells, melanocytes, odontocytes, cardiac septa, branchial arches of head and neck

39
Q

How is the neural plate formed?

A

The notochord prompts thickening of midline ectoderm into neuroectoderm

40
Q

Underlying _______ expands to raise neural _____, forming the neural ______

A

Mesoderm; folds; groove

41
Q

What structure is formed by the fusion of neural fold crests around the neural groove?

A

Neural tube

42
Q

What specialized layer lines the neural tube and what will it derive?

A

Neuroectoderm => nervous system

43
Q

What is the derivitive of the ectoderm overlying the dorsal aspect and neural tube?

A

Skin

44
Q

From what are the neural crest cells derived?

A

Dorsal neuroectoderm

45
Q

Why are nc cells also called ectomesenchyme?

A

They are neuroectoderm cells that transform to migrate

46
Q

What region closes first during neurulation?

A

Occipitoervical, then cranial neuropore on day 25

47
Q

What type of tissue makes up the near epithelium?

A

Pseudo-stratified

48
Q

What occurs in the first differentiation wave of neuroepithelium histo-genesis

A

Neurons migrate externally where somas form the mantle layer and axons project externally(becomes grey matter) to form the marginal layer(becomes white matter)

49
Q

What occurs in the second differentiation wave of neuroepithelium histo-genesis

A

Glioblasts form the astrocytes and oligodendrocytes of CNS

50
Q

What occurs in the third differentiation wave of neuroepithelium histo-genesis

A

Ependyma remain deep to line ventricles and central canal

51
Q

Neural crest cell ns derivatives

A

PNS; satellite cells, schwan cells, neurons

52
Q

Neuroepithelial cells NS derivatives

A

CNS; neurons, glioblasts of CNS, ependymal cells

53
Q

What is formation and role of roof plate?

A

Formation induced by surface ectoderm; root plate secretes BMP, promoting dorsalization

54
Q

Describe role + formation of floor plate?

A

Formation induced by notochord(which is ventral to neural tube); floor plate secretes shh which promotes centralization

55
Q

What results from the opposing actions of BMP and shh?

A

Establishment of a sharp boundary dividing neural tube into ventral and dorsal halves, visually separated by the sulcus limitans

56
Q

Dorsal cells form the______ plate and differentiate into _____ neurons

A

Alar plate; sensory

57
Q

Ventral cells form the_____ plate and differentiate into _____ neurons.

A

Basal; motor

58
Q

In what region does the dorsal-ventral axis of the alar + basal plates NOT occur?

A

Forebrain

59
Q

What kind of neurons form in the alar plate?

A

Association neurons

60
Q

What kind of neurons form in the basal plate?

A

Multipolar

61
Q

Why does the caudal equina form?

A

Overall fetal growth outpaces the growth of the neural tube

62
Q

How are neural take defects detected?;

A

US. Amniotic AFP

63
Q

Folic acid

A

Reduces neural tube defects; fortified cereal grains

64
Q

NT defect incidence (excluding spina bifida occulta)

A

1 in 1000

65
Q

Dysraphism

A

Group of con genital abnormalities that effect the spine, spinal cord, and nerve roots. Greek for bad suture

66
Q

Characteristics of spina bifid occulta

A

Failure of dorsal vertebral arch formation; often only visible by overlying patch of dark hair. Typically no neurodeficit.

67
Q

Meningocele

A

Failure of dorsal vertebral arch formation with ballooning meninges; visibly indicated by overlying bulge; typically no near deficit if no neural tissue involved

68
Q

Myelomeningocele

A

Failure of dorsal vertebral arch formation with ballooning meninges and involvement of neural tissue outside the vertebral column ; visibly indicated by overlying bulge; typically, inferior neural deficits

69
Q

Myeloschisis (or Rachischisis)

A

Failure of neural tube to fully fold during neurulation, leaving neural tissue open to the air fetus is typically nonviable.

70
Q

How do neural crest cells reach their final destination?

A

By migrating along defined pathways

71
Q

Neurocristopathies

A

Result of neural crest cells failing to migrate

72
Q

2 examples of neurocristopathies

A

Hirschsprung’s disease (aganglianic megacolon)
CHARGE syndrome (coloboma, heart anomalies, atresia of choana, retardation of growth + development, genital anomalies, and ear anomolies)

Human Structure (10 decks)

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