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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
What germ layer spreads through embryoblast?
Mesoderm
26
What forms the notochord?
Midline mesoderm
27
________ migrates __________ to reach the extra embryonic mesoderm
Mesoderm; laterally
28
Mesoderm migrates cranially to form the __________ region
Cranially, cranial to oropharyngeal membrane
29
Mesoderm fills the entire trilaminardisk, except....
At the oropharyageal+cloacal membranes
30
What components make up the tri laminar disk after gastrulation is complete?
Dorsal to ventral: ectoderm, mesoderm, endoderm with the notochord running through the mesoderm cranial to caudal
31
What happens to the primitive streak as the notochord forms?
It regresses.
32
What is the clinical result of failure of primitive streaksí streak regression?
Sacrococoygeal teratoma
33
When does neurulation begin and end?
Begin at end of 3rd week; resolves by end of 4th week.
34
What directs neurulation?
The notochord.
35
Where is neural plate formed?
In midline over the notochord, from ectoderm
36
How is the neural tube formed?
Dorsal folding of neural plate
37
What occurs as the neural tube closes?
Neural crest cells begin migration
38
Name some derivatives of neural crest cells
Neuralgia, PNS ganglia, chromaffin cells, melanocytes, odontocytes, cardiac septa, branchial arches of head and neck
39
How is the neural plate formed?
The notochord prompts thickening of midline ectoderm into neuroectoderm
40
Underlying _______ expands to raise neural _____, forming the neural ______
Mesoderm; folds; groove
41
What structure is formed by the fusion of neural fold crests around the neural groove?
Neural tube
42
What specialized layer lines the neural tube and what will it derive?
Neuroectoderm => nervous system
43
What is the derivitive of the ectoderm overlying the dorsal aspect and neural tube?
Skin
44
From what are the neural crest cells derived?
Dorsal neuroectoderm
45
Why are nc cells also called ectomesenchyme?
They are neuroectoderm cells that transform to migrate
46
What region closes first during neurulation?
Occipitoervical, then cranial neuropore on day 25
47
What type of tissue makes up the near epithelium?
Pseudo-stratified
48
What occurs in the first differentiation wave of neuroepithelium histo-genesis
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
What occurs in the second differentiation wave of neuroepithelium histo-genesis
Glioblasts form the astrocytes and oligodendrocytes of CNS
50
What occurs in the third differentiation wave of neuroepithelium histo-genesis
Ependyma remain deep to line ventricles and central canal
51
Neural crest cell ns derivatives
PNS; satellite cells, schwan cells, neurons
52
Neuroepithelial cells NS derivatives
CNS; neurons, glioblasts of CNS, ependymal cells
53
What is formation and role of roof plate?
Formation induced by surface ectoderm; root plate secretes BMP, promoting dorsalization
54
Describe role + formation of floor plate?
Formation induced by notochord(which is ventral to neural tube); floor plate secretes shh which promotes centralization
55
What results from the opposing actions of BMP and shh?
Establishment of a sharp boundary dividing neural tube into ventral and dorsal halves, visually separated by the sulcus limitans
56
Dorsal cells form the______ plate and differentiate into _____ neurons
Alar plate; sensory
57
Ventral cells form the_____ plate and differentiate into _____ neurons.
Basal; motor
58
In what region does the dorsal-ventral axis of the alar + basal plates NOT occur?
Forebrain
59
What kind of neurons form in the alar plate?
Association neurons
60
What kind of neurons form in the basal plate?
Multipolar
61
Why does the caudal equina form?
Overall fetal growth outpaces the growth of the neural tube
62
How are neural take defects detected?;
US. Amniotic AFP
63
Folic acid
Reduces neural tube defects; fortified cereal grains
64
NT defect incidence (excluding spina bifida occulta)
1 in 1000
65
Dysraphism
Group of con genital abnormalities that effect the spine, spinal cord, and nerve roots. Greek for bad suture
66
Characteristics of spina bifid occulta
Failure of dorsal vertebral arch formation; often only visible by overlying patch of dark hair. Typically no neurodeficit.
67
Meningocele
Failure of dorsal vertebral arch formation with ballooning meninges; visibly indicated by overlying bulge; typically no near deficit if no neural tissue involved
68
Myelomeningocele
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
Myeloschisis (or Rachischisis)
Failure of neural tube to fully fold during neurulation, leaving neural tissue open to the air fetus is typically nonviable.
70
How do neural crest cells reach their final destination?
By migrating along defined pathways
71
Neurocristopathies
Result of neural crest cells failing to migrate
72
2 examples of neurocristopathies
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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