Lecture 9: Germ Layer

Question 1

morphogenetic movement.

Answer 1

The most important event in gastrulation is morphogenetic movement.

Question 2

A secondary consequence of gastrulation…

Answer 2

is the development of a three-germ layer embryo (triploblasty)

Question 3

When does differentiation happen?

Answer 3

during gastrulation

Question 4

That cellular movement during gastrulation is active, not passive, is also demonstrated by

Answer 4

bottle cells

Question 5

Two-germ layer stage:

Answer 5

initial state of the embryo is 2 layers of germ cells: Epiblast, hypoblast

Question 6

What is the role of nanog and Gata 6 in the establishment of these two layers?

Answer 6

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Question 7

Gastrulation:

Answer 7

Occurs at the end of the second week of gestation.
Knowledge is primarily based on gastrulation in birds.
Three embryonic germ layers form during this stage:
• Ectoderm • Mesoderm • Endoderm

Question 8

Describe the formation of the primitive streak.

Answer 8

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Question 9

What roles might Wnt and TGF-β play in the formation of the formation of the primitive streak?

Answer 9

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Question 10

What are the three classical molecular markers expressed by nodal cells?

Answer 10

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Question 11

What are “bottle cells” and what role do they play in gastrulation?

Answer 11

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Question 12

Describe the regression of the primitive streak.

Answer 12

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Question 13

What roles are played in the gastrulation by hyaluronic acid,
fibronectin, and BMP-4?

Answer 13

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Question 14

Describe the formation of the notochord and list its various functions as a primary inductor.

Answer 14

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Question 15

Describe the role of E-cadherin and N-cadherin in the epithelial-mesenchymal transition.

Answer 15

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