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EMBRYO Exam #1- Lo > 02-03: Nervous System Induction > Flashcards

02-03: Nervous System Induction Flashcards

1
Q

What are the steps of the formation of the notochord?

A

1- Cellular precursors of the notochord migrate ANTERIORLY and then are left behind as a rodlike aggregation as the primitive streak regresses

2- Notochordal cells fuse with flanking endodermal cells

3- Temporarily form a neutrenteric canal

4- Notochord cells separate from the endoderm

5- Aggregate to form a solid definitive notochord

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2
Q

Which layer invaginated through the primitive streak?

A

mesoderm

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3
Q

Which layer is continuous with the ectoderm of the amnion?

A

ectoderm

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4
Q

Which layer is lacking at the oropharyngeal plate?

A

mesoderm

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5
Q

What are some of the inductive functions of the notochord?

A
  • Formation of axial structures
  • Induces overlying ectoderm to convert to neural ectoderm
  • Specifies identity of certain cells within the early nervous system
  • Transforms certain mesodermal cells of the somites into vertebral bodies
  • Stimulates earliest steps in the development of the pancreas
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6
Q

What is a signal that is used in the notochord’s formation of many axial structures?

A

Shh

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7
Q

What are 2 signals that are involved in the notochord’s induction of overlying ectoderm conversion to neural ectoderm?

A
  • Noggin

- Chordin

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8
Q

What are 2 transcription factors that are involved in the notochord’s induction of overlying ectoderm conversion to neural ectoderm?

A
  • Foxa-2

- Goosecoid

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9
Q

What is also referred to as the head organizer?

A

prechordal plate

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10
Q

What forms the prechordal plate?

A

early cells that pass through the primitive node

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11
Q

What is the prechordal plate a source of signals for?

A
  • Shh (involved in the ventral patterning of the forebrain)

- Survival of neural crest cells that emigrate (move away) from the early forebrain

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12
Q

What does Wnt3 do?

A

induces expression of Nodal

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13
Q

What does Nodal do?

A
  • establishes a posterior signaling center which induces formation of the primitive streak
  • induces primitive streak and helps to establish Left-Right symmetry
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14
Q

What does Noggin do?

A

neural inducer

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15
Q

What does Chrodin do?

A

neural inducer

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16
Q

What does Goosecoid do?

A

activates genes (chrodin & noggin)

17
Q

What does Foxa-2 do?

A
  • establishment of primitive node
  • initiates notochord function
  • establishes midline structures cranial to node
18
Q

What does Shh do?

A

induces axial structures

19
Q

What are the 2 experiments showing neural induction?

A
  • Amphibian: Dorsal lip of blastopore in embryo induces a secondary embryo to form
  • Mammals: Primitive node graft from one embryo induces the formation of a secondary neural tube in another embryo
20
Q

What is the notochord a primary inducer of?

A

formation of neuroectoderm

21
Q

What is determination?

A
  • a cell or part of an ambryo becomes restricted to a given developmental pathway
  • a cell becomes committed to a specific cell line

**precedes differentiation

22
Q

What is differentiation?

A

a complex of changes involved in the progressive specialization of structure and function

**resulting in the formation of luxury molecules

23
Q

What are 5 examples of left-Right Asymmetry?

A
  • heart
  • looping of gut
  • liver
  • spleen
  • lung lobation
24
Q

What is the first sign of asymmetry?

A

the beating of cilia around the primitive node&raquo_space; causes a directional current and expression of TGF-b molecules

25
Q

What are the 2 TGF-b molecules the are expressed at the beginning of asymmetry?

A
  • Nodal [symmetry breaking molecule on L side of embryo]

- Lefty1 [L side of primitive streak]

26
Q

Which somite stages does asymmetrical current occur?

A

between somite stage 2-6

27
Q

How does Nodal help determine asymmetry?

A
  • Swept to the L side of primitive node by ciliary current

- Stimulates multiple gene expression pathways

28
Q

How does Nodal stimulate multiple gene expression pathways?

A

Pitx-2

29
Q

How does Lefty1 help determine asymmetry?

A
  • Expression on L side of embryo

- Blocks diffusion of molecules to the R side

30
Q

What are 3 additional factors that help determine asymmetry?

A
  • Shh
  • Retinoic acid
  • FGF-8
31
Q

What CAMs are in the preinduced ectoderm?

A

N-CAM

E-cadherin

32
Q

What CAM is in the ectoderm?

A

E-cadherin

33
Q

What CAMS are in the neural tube?

A

N-CAM

N-cadherin

EMBRYO Exam #1- Lo (12 decks)

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