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EMBRYO Exam #1- Lo > 02-05: Body Plan Development I > Flashcards

02-05: Body Plan Development I Flashcards

1
Q

What are the stages of neural tube development?

A

1- Formation of thickened neural plate

2- Shaping of neural plate

3- Folding of neural plate

4- Formation of neural tube

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2
Q

What happens during the formation of thickened neural plate stage of neural tube development?

A
  • columnarization of midline ectodermal cells overlying notochord
  • CUBOIDAL&raquo_space; COLUMNAR
  • involves microtubules
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3
Q

What happens during the shaping of the neural plate stage of neural tube development?

A
  • process of convergent extension

- rectangle&raquo_space; space

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4
Q

What role does planar polarity play in the shaping of neural plate stage of neural tube development?

A

-

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5
Q

What are the 2 hinge points of the neural tube?

A
  • Median hinge point

- Lateral hinge point

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6
Q

What is the median hinge point during the folding stage of the neural plate?

A
  • induced by notochord to cause folding

- COLUMNAR&raquo_space; PYRAMIDAL

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7
Q

What is the lateral hinge point during the folding stage of the neural plate?

A

completes the folding process

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8
Q

What elevates the neural folds during the folding stage of the neural plate?

A

pushing inward by expanding surrounding non-neural epithelium

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9
Q

What causes the formation of the neural tube?

A

fusion of apical surfaces of neural folds

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10
Q

What is the formation of the neural tube mediated by?

A

glycoconjugates

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11
Q

Where does the formation of neural tube begin?

A

MIDWAY along the neural tube (21-22 days)

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12
Q

Where does the neural tube extend?

A

cranially&raquo_space; caudally

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13
Q

When do the Anterior and Posterior neuropores of the neural tube form?

A

day 23

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14
Q

What causes the columnar cells to transform into wedge cells?

A

actin & myosin

**contractile mechanism at one end of the cell and not the other end of the cell

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15
Q

What induces neural tube segmentation?

A
  • notochord
  • anterior visceral endoderm
  • chordal plate

** +Wnt8 gradient

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16
Q

Where does segmentation occur?

A

in an existing tubular structure

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17
Q

What are the 3 organizing (signaling) centers in neural tube segmentation?

A
  • isthmic organizer
  • anterior neural ridge
  • zona limitans
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18
Q

What is the isthmic organizer important for during neural tube segmentation?

A

important for organizing the midbrain and cerebellum

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19
Q

What does the isthmic organizer secrete?

A

Wnt1

FGF8

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20
Q

What is the anterior neural ridge important for during neural tube segmentation?

A

important for organizing (ventral aspect of forebrain):

  • telencephalon
  • parts of diencephalon
  • olfactory area
  • pituitary gland
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21
Q

What does the anterior neural ridge organizer secrete?

A

Shh

FGF8

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22
Q

What is the zona limitans important for during neural tube segmentation?

A

important for organizing the border between the dorsal and ventral thalamus

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23
Q

What does the zona limitans secrete?

A

Shh

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24
Q

What do the rhombencephalon segmentation genes do?

A

set up basic pattern of segmentation in the hindbrain

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25
Q

What does Krox 20 demarcate?

A

r3

r5

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26
Q

What do Kreisler and Hoxa1 demarcate?

A

r5

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27
Q

What does the Retinoic acid gradient demarcate?

A

r4-r7

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28
Q

What does Gbx2 demarcate?

A

r1-r3

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29
Q

What does the pattern of Hox gene expression determine?

A

cranial nerves and pharyngeal arch derivatives

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30
Q

What stimulates the expression of Hoc genes?

A

Retinoic acid gradient&raquo_space; initiates expression of Hoxa1 and Hoxb1

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31
Q

What does Retinoic acid do?

A

sets up a gradient

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32
Q

What part of the neural plate possesses the properties of a stem cell zone?

A

the caudal most part

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33
Q

What happens if Retinoic acid inhibits FGF8?

A

mitosis will not occur&raquo_space; differentiation

34
Q

Why is neural crest tissue sometimes considered to be a 4th germ layer?

A

forms many structures

35
Q

What are the sensory placodes?

A

thickenings in overlying ectoderm (sensory ganglia)

36
Q

What is the origin of the sensory (ectodermal) placodes?

A

from ectoderm or neural crest

37
Q

What are the 3 zones of mesoderm?

A
  • paraxial (segmental plate) mesoderm
  • intermediate mesoderm
  • lateral plate mesoderm
38
Q

Which mesoderm zone is closest to the notochord?

A

paraxial/segmental plate mesoderm

39
Q

What is a coelom?

A

cavity lined with mesoderm

  • thoracic
  • pericardium
  • abdominal
40
Q

What are somitomeres?

A

initial pairs of segments of mesenchyme that begin to develop along and on either side of the neural plate in the paraxial mesoderm

**barely discernable as segments

41
Q

When are new somitomeres added?

A

added caudally as the primitive streak regresses

42
Q

What happens after 20 pairs of somitomeres have formed (day 20)?

A

the first pair of somites form behind (caudal to) the 7th pair of somitomeres

43
Q

What are somites?

A

more dense blocks of mesoderm that form along the notochord

44
Q

What happens to a pair of somitomeres every few hours?

A

a pair of somitomeres is transformed in the caudal direction into a pair of somites

45
Q

What happens as a pair of somites are formed?

A

pairs of somitomeres are also formed at the ANTERIOR end of the primitive node

46
Q

What occurs because of the transformation and formation of somites?

A

11 pairs of somitomeres are kept constant at the causal end of the paraxial mesoderm

47
Q

What are the 2 mechanisms involved in somitogenesis?

A
  • Wavefront

- Segmentation clock

48
Q

What results in a cessation of somitogenesis?

A

the balance between the opposing gradients of:

  • Retinoic acid
  • FGF8
49
Q

What do oscillating molecules in the Notch pathway lead to?

A

a defining of the Anterior and Posterior borders of each somite

Stimulate the expression of:
-Lunatic fringe = at Anterior border of a future somite

-C-Hair = at Posterior border of a future somite

50
Q

Where is the Retinoic acid gradient strongest?

A

cranial

51
Q

Where is the FGF gradient strongest?

A

caudal

52
Q

What do ephrins do?

A

maintain the intersomitic spaces

53
Q

What role does the down regulation of Snail play in somitogenesis?

A

-

54
Q

What are the 4 features of the history of a somite?

A
  • epithelial stage
  • epitheliomesenchymal transformation stage
  • separation of the myotome
  • breakup of epithelial dermatome into dermal fibroblasts
55
Q

What are the sclerotome ventral derivatives?

A
  • ventral bodies

- their intervertebral disks

56
Q

What are the sclerotome lateral derivatives?

A
  • distal ribs

- some tendons

57
Q

What are the sclerotome dorsal derivatives?

A
  • dorsal part of neural arch

- spinous process

58
Q

What are the sclerotome central derivatives?

A
  • pedicles and ventral parts of neural arches
  • proximal ribs
  • transverse processes of vertebrae
59
Q

What are the sclerotome medial (meningotome) derivatives?

A
  • meninges

- BV of meninges

60
Q

What are the arthrotome derivatives?

A
  • intervertebral disks
  • vertebral joint sufaces
  • proximal ribs
61
Q

What are the dermatome derivatives?

A
  • dermis

- blade of scapula

62
Q

What are the dorsomedial myotome derivatives?

A

intrinsic back muscles (epaxial)

63
Q

What are the ventrolateral myotome derivatives?

A

limb muscles or muscles of ventrolateral body wall (hypaxial)

64
Q

What are the neurotome derivatives?

A

endoneurial and perineruial cells

65
Q

What are the sydentome derivatives?

A

tendons of epaxial musculature

66
Q

What is a dermomyotome?

A

the dorso-lateral part of a somite

67
Q

What creates a balance that commits the myotome portion of the somite to commit to the myogenic lineage?

A
  • Shh signaling from the notochord

- Wnt signaling from the dorsal neural tube

68
Q

What does Noggin do?

A
  • inhibits BMP4 which would normally inhibit myogenesis

- allows myogenesis to occur

69
Q

What produces BMP4?

A

the lateral plate

70
Q

What does BMP4 do?

A
  • suppresses myogenesis in the ventrolateral dermomyotome

- stimulates cells from this area to migrate from the somite into the limb bud

71
Q

What produces FGF?

A

the myotome

72
Q

What does FGF do?

A

signals the sclerotome to produce scleraxis

73
Q

What does scleraxis do?

A

causes Anterior and Posterior borders of each somite to form the syndetome

74
Q

What is the syndetome?

A

the precursor of tendons

75
Q

What does the sclerotomal portion of each somite break up into?

A

an Anterior and a Posterior portion

76
Q

What creates gaps that allow nerves to grow out from the neural tube into the epaxial segmental musculature?

A

the joining of the posterior portion of one somite and the anterior portion of an adjacent somite

77
Q

What does the future intermediate mesoderm respond to, to become intermediate mesoderm?

A
  • BMP [from lateral ectoderm]

- activin [from paraxial mesoderm]

78
Q

What does the intermediate mesoderm form?

A
  • pronephros

- mesonephros (later)

79
Q

Which way do the heart-forming cells move through the primitive streak?

A

caudal&raquo_space; cranial

80
Q

Where is the cardiac crescent located?

A

on the cranial end

81
Q

Where is the first blood cell from?

A

yolk sac

EMBRYO Exam #1- Lo (12 decks)

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