Chapter 5 - 3rd Week of Development: Trilaminar Germ Disk Flashcards Preview

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Flashcards in Chapter 5 - 3rd Week of Development: Trilaminar Germ Disk Deck (46):
0

What happens during gastrulation?

All the three germ layers (ectoderm, mesoderm, endoderm) are established.

1

When does the gastrulation begin?

It begins with the formation of the primitive streak on the surface of epiblast

2

When is the streak vaguely defined?

day 15-16

3

*Which proteins controls cell invagination in gastrulation?

Fibroblast growth factor 8 (FGF8)

4

Where is fibroblast growth factor 8 (FGF8) synthesized?

It is synthesized by the streak cells

5

How does the FGF8 regulate the cell specifitcation into the mesoderm?

By regulating Brachyury (T) expression

6

What is the source for all germ layers?

The epiblast

7

What happens when the cloacal membrane dissapears?

The posterior wall of the yolk sac forms a small diverticulum that extends into the connecting stalk

8

Primitive node

- Is the cephalic end of the steak.
- Consists of a slightly elevtaed area surrounding the small primitive pit

9

Invagination

Is the migration of the epiblast towards the primitive streak. Upon arrival in the region of the streak, they become flask-shaped, detach from epiblast, and slip beneath it.

10

When does the allantoenteric diverticulum, or allantois, appear?

Around the 16th day of development

11

The cloacal membrane

- Formed at the caudal end of the embryonic disk
- Consists of an endoderm and ectoderm adherent
- No intervenning mesoderm

12

Anterior visceral endoderm (AVE)

- Express genes essential for head formation
- The genes essential for head formation is:
* The transcription factors
> OTX2
> LIM1
> HESX1
* secreted factors
> Cerebrus
> Lefty

13

What inhibits the nodal activity in the cranial end of the embryo?

Cerebru and lefty

14

What maintains and initiate the primitive streak?

The expression of Nodal

15

Nodal is a member of....

Transforming growth factor-B

16

The nodal is responsible....

for formation of dorsal and ventral mesoderm adn head and tail structures

17

Which are members of transforming growth factor?

- Nodal
- Bone morphogenic protein 4 (BMP4)

18

Where can we find Bone morphogenic protein 4 (BMP4)

BMP4 is secreted throughout the embryonic disk

19

Which part of the embryo is the organizer?

The node is the organizer, becuase BMP4 is not blocked by other genes expressed in the node.

20

HNF-3B

Maintains the node adn later induces regional specifity in the forebrain and the midbrain areas

21

Goosecoid

Activates inhibitors of BMP4 contributes to regulation of head development.

22

Brachyury (T) gene

- Control the regulation of dorsal mesoderm formation in middle and caudal regions of the embryo.
- Is essential for cell migration through the primitive streak

23

Where is Brachyury (T) gene expressed?

It is expressed in the node, notochord precusor cells, and notochord.

24

Brachyury

Encodes a sequence-specific DNA binding protein that function DNA binding protein that functions as a transcription factor

25

the T-box

- Is the DNA binding domain.
- Hvae more than 20 genes

26

FG8 maintains...

nodal expression as well as LEFTY-2. And both of these genes upregulate PITX

27

Which homeobox-containing transcription factor is responsible for establishing left sideness?

PITX2

28

Situs inversus and dextrocardia (placement of the heart to the right side) is caused by...

the gene PITX2 being expressed ectopically (e.g on the right side)

29

LEFTY and Sonic hedgehog (SHH)

prevent left sided signals from crossing over

30

Brachyury (T) is essential for expression

of Nodal, LEFTY-1, and LEFTY-2

31

Monoamine oxidase (MAO)

- Breaks down serotonin (5HT)
- Is upstream form FGF8

32

Changes in 5HT signaling result in:

- Setus inversus
- Dextrocardia
- Other heart defects

33

What does cells that ingress through the cranial region of the node become?

They become the prechordal plate and the notochord

34

What does those cell who migrate at the lateral edges of the node and form the cranial end of the streak become?

They become paraxial mesoderm

35

Cells who migrate trough the midstreak region become...

Intermediated mesoderm

36

Those cells who migrate through the more caudal part of the streak form....

lateral plate mesoderm

37

Where does the cells migrating through the caudalmost part of the streak contribute to?

They contribute to extraembryonic mesoderm

38

What characterize the trophoblast by the beginning of the thrid week?

The trophoblast is characterized by primary villi that cosists of a cytotrophoblastic core covered by a syncytial layer.

39

Secondary villus

Is the structure we get when mesodermal cells penetrate the core of primary villi and grow toward the decidua.

40

When does the mesodermal cells in the core of the villus begin to differentiate into blood cells and small blood vessles?

By the end of third week

41

When do we get the villus capillary system?

By the end of third week, when the mesodermal cells in the core of the villus differentiate into blood cells and small blood vessles.

42

Other names for the villus?

- Tertiary villus
- Definitive placental villus

43

What connects the placenta to the embryo?

- Capillaries in tertiary villi make contact with capillaries developing in the mesoderm of the chorionic plate and in the connecting stalk.
- These vessels, in turn, establish contact with the intraembryonic circulatory system

44

When does the heart begins to beat?

- In the 4th week of development

45

When the heart begins to beat....

the villous system is ready to supply the embryo proper essential neutriens and oxygen.