Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

vertebrate development > gastrulation > Flashcards

gastrulation Flashcards

1
Q

what is gastrulation

A

the process that produces the three germ layers: ectoderm, mesoderm and endoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the three primary germ layers

A

ectoderm (outer), endoderm (inner) and mesoderm (middle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what cells are derived from the ectoderm

A

epidermal cells of the skin
neurons of the brain
pigment cell (melanocyte)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what cells are derived from the mesoderm

A

notochord, bone tissue, tubule cell of the kidney, red blood cells, facial muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what cells are derived from endoderm

A

stomach cells, thyroid cells, alveolar cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what 5 major morphogenetic movements occur during gastrulation

A
  • Invagination: in folding of cell sheet into embryo
  • Involution: in turning of cell sheet over the basal surface of an outer layer
  • Ingression: migration of individual cells into the embryo
  • Delamination: splitting of one cell sheet into two more or less parallel sheets
  • Epiboly: the expansion of one cell sheet over other cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the three types of invagination

A
  1. Apical constriction
  2. Apical tractoring – movement of cells laterally, converging into the inside, the cells are detached at the bottom
  3. Swelling of proteoglycan – ECM makes physical constraint, pushing inside the embryo
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the difference between invagination vs evagination

A

in invagination the sheet forms an in pocketing towards the basal side
Evagination is the out pocketing towards the apical side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is involution

A

Starting with the sheet of epithelium expanding and turning over on itself
Bulk movement of tissue by rolling inward continues and forms new tissue sheets - collective movement driven by leader cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is delamination

A

Splitting off one cellular sheet into two approximately parallel sheets
Formation of a new (additional) epithelial sheet of cells
Leads to the specification of new germ layer
(produces the epiblast and hypoblast from the ICM)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is ingression

A

Individual cells leave epithelial sheet and undergo epithelial to mesenchymal transition (EMT)
They lose adhesion, alter their shape and become migrating mesenchyme cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what happens when primary mesenchymal cells loose their cadherin complex components

A

– Lose affinity for neighboring epithelial cells
– Lose affinity for the hyaline layer on the exterior of the embryo
– Gain affinity for the basal lamina
Acquire ability to migrate and move from original site
Become more elongated cells. In order to specify the mesoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is epiboly

A

movement of epithelial sheet, spreading out of an overlying sheet of cells over an underlying mass of stationary tissue (Enclose deeper tissues)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

where does gastrulation begin in amphibians

A

in the grey crescent (opposite the point of sperm entry)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how does the amphibian egg have polarity before fertilisation

A

a dense yolk material in the vegetal pole and very little yolk in the animal pole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what happens at the point of sperm entry in amphibians

A

develops polarity
sperm centrioles organise the centrosomes and microtubules to set up the mitotic spindle in the animal pole
determines the ventral dorsal axis of the embryo
formation of the dorsal blastopore lip

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what happens opposite the point of sperm entry in an amphibian egg

A

the cortical cytoplasm rotates relative to the internal cytoplasm - facilitated by the formation of microtubules in the vegetal hemisphere
where development begins with the formation of the grey crescent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

where does gastrulation begin in the amphibian egg

A

the dorsal blastopore lip (invagination occurs here)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the marginal zone?

A

region of the equator where the vegetal and animal hemispheres meet (in amphibian egg)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are bottle cells

A

epithelial cells found at the initial site of gastrulation, temporarily become bottle-shaped by bottle (apical) constriction - helps invagination movement, bringing superficial cells from the marginal zone to involute and specify into mesoderm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

in the initial stages of frog gastrulation what cells drive specification of the mesoderm

A

marginal zone superficial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is vegetal rotation and what generates it

A

a morphogenetic movement that drives mesoderm internalization during gastrulation in amphibian embryos. - invagination generates vegetal rotation helping superficial cells to involute

23
Q

what becomes the notochord in frog egg

A

dorsal midline mesoderm

24
Q

what is cortical rotation

A

rotation of the cortical cytoplasm caused by reorganisation of microtubules into parallel formation leading to the appearance of the grey crescent

25
Q

where must the first cleavage be in the amphibian egg

A

first cleavage must go through the grey crescent - to establish full polarity and ensure proper left right symmetry

26
Q

what happens in early gastrulation of amphibian eggs

A

1) The bottle cells of the margin invaginate and move inward to form the dorsal lip of the blastopore, and 2) the mesodermal precursors involute under the roof of the blastocoel and migrate apically. Involution of the mesodermal precursors is driven by vegetal rotation in the endoderm

27
Q

what happens in mid gastrulation in amphibian eggs

A

1) The archenteron forms and displaces the blastocoel, and
2) cells migrate from the lateral and ventral lips of the blastopore into the embryo.
3) The cells of the animal hemisphere migrate down toward the vegetal region

28
Q

what happens in late gastrulation of amphibian eggs

A

1) The blastocoel is obliterated,
2) the embryo becomes surrounded by ectoderm through epiboly,
3) the endoderm has been internalized, and
4) the mesodermal cells have been positioned between the ectoderm and endoderm

29
Q

what does the epiblast give rise to

A

the three germ layers of the embryo proper

30
Q

what does the hypoblast contribute to

A

the extraembryonic mesoderm and yolk sac

31
Q

what is the hypoblast essential for during gastrulation - experimental removal results in what

A

essential for embryo patterning - removal results in the formation of the multiple primitive streaks

32
Q

gastrulation begins with the formation of….

A

…the primitive streak on the dorsal surface of the epiblast

33
Q

invagination of epiblast cells becomes which layer

A

invading and displacing the hypoblast cells to become endoderm

34
Q

what morphogenetic movement causes formation of the mesoderm and what drives it

A

ingression of epiblast cells - driven by epithelial-to-mesenchymal transition (EMT) through loss of E-cadherin

35
Q

what cells become the ectoderm layer

A

the epiblast cells remaining on the the sruface

36
Q

describe the formation of the three germ layers

A

starting with the formation of the primitive streak where the invagination of epiblast cells invades and displaces the hypoblast cells to become endoderm
loss of E-cadherin results in the epithelial to mesenchymal transition (EMT) that drives ingression of epiblast cells forms the mesoderm
the epiblast cells remaining on the surface become ectoderm

37
Q

when does gastrulation occur

A

week 3

38
Q

how long does gastrulation last

A

a week

39
Q

describe the TGF-β-mediated specialisation of the mesoderm

A
  • The vegetal region of the oocyte accumulates maternal mRNA for the transcription factor VegT and mRNA for the Nodal paracrine factor Vg1
  • At the late blastula stage, the Vg1 mRNA is translated and Vg1 induces the future dorsal mesoderm to transcribe the genes for several Wnt antagonists(inhibition ofWnt)
  • The VegT message is also translated, and VegT activates nuclear genes encoding Nodal proteins
  • Nodal activates the expression of the transcription factor Eomesodermin (Eomes) in the presumptive mesoderm
  • Eomes, with the help of activated Smad2 from the Nodal proteins, activates nuclear genes encoding VegT (feedforward loop)
40
Q

who discovered the amphibian organiser

A

1924 - Hilde mangold discovered the organiser, a PhD student, she died and Hans Spemann took all the credit.

41
Q

what structures form the amphibian organizer

A

The dorsal lip cell and gray crescent form the amphibian organizer:

42
Q

what does the amphibian organiser do

A

initiates gastrulation and patterns the embryo
 Ability to self-differentiate dorsal mesoderm
 Ability to dorsalize surrounding mesoderm into paraxial mesoderm
 Ability to dorsalize the ectoderm, inducing the formation of the neural tube
 Ability to initiate movements of gastrulation

43
Q

in the experiments of Mangold and Spemann where they transplanted neural ectoderm into a different region of a newt embryo what did they observe.

A

(A) When the tissues are transferred between early gastrulae, the presumptive neural tissue develops into epidermis, and only one neural plate is seen
(B) When the same experiment is performed using late-gastrula tissues, the presumptive neural cells form neural tissue, thereby causing two neural plates to form on the host.

44
Q

what conclusions were made from the Mangold - Spemann experiment on newt embryos

A
  1. Cells of the early gastrula exhibit conditional (induction-dependent) specification
  2. Cells of the late gastrula exhibit autonomous (mosaic, independent) specification. They are determined
45
Q

what happens if you transplant the dorsal lip into another gastrula

A

The donor tissue invaginates and forms a second archenteron, and then a second embryonic axis. Both donor and host tissues are seen in the new neural tube, notochord, and somites
Eventually, a second embryo forms joined to the host.

46
Q

the cells of the amphibian organiser contribute to which 4 cell types

A

1) pharyngeal endoderm, 2) head mesoderm (prechordal plate), 3) dorsal mesoderm (notochord), and 4) the dorsal blastopore lip

47
Q

what does the dorsal blastopore lip become

A

becomes the chordaneural hinge that induces the tip of the tail

48
Q

the (amphibian) dorsal mesoderm induces….

A

the hindbrain and trunk

49
Q

the pharyngeal endoderm and prechordal plate lead to the migration of the organiser tissue to induce what

A

the forebrain and midbrain

50
Q

what paracrine factors are secreted by the organiser to specify the neural plate

A

Noggin, Chordin and Cerberus

51
Q

what is goosecoid

A

a transcription factor that specifies the dorsal mesoderm, which becomes the organizer

52
Q

describe the mechanism of organiser induction via β-catenin-mediated dorsal signals

A

a) Before fertilization, Dsh and GSK3-binding protein (GBP) associate kinesin at the vegetal pole. and Wnt11 mRNA is in vesicles at the vegetal portion.
b) After fertilization, the vegetal vesicles are translocated dorsally along subcortical microtubule tracks. Cortical rotation adds a “slow” form of diffusion of Wnt11 mRNA
c) Wnt11, Dsh, and GBP are then released from the microtubules and are distributed in the future dorsal region of the 1-cell embryo
d) Dsh and GBP bind to and block the action of GSK3, thereby preventing the degradation of β-catenin on the dorsal side of the embryo. Wnt11 amplifies Dsh-mediated β-catenin stabilization
e) The nuclei of the blastomeres in the dorsal region recieve stable β-catenin, in the ventral nuceli it is degraded.
f) During cleavage, β-catenin enters the nuclei and binds with Tcf3 to form a transcription factor that activates genes encoding proteins Siamois and Twin
g) Siamois and Twin interact with the Smad2 transcription factor activated by vegetal TGF-β family members (Nodal-related proteins, Vg1, etc.).
h) Together, these three transcription factors activate the “organizer” genes such as chordin, noggin, and goosecoid (producing the organiser proteins)

53
Q

what is Xnr, what is it activated by

A

Xenopus nodal related genes - activated by β-catenin synergistic action with Vg1 and VegT

54
Q

what happens in mesodermal regions with low and high regions on Xnr

A
  • Mesodermal regions with little or no Xnr have high levels of BMP4 and Xwnt8; they become ventral mesoderm
  • Mesodermal regions with high concentration of Xnr activate expression of Goosecoid and other dorsal mesodermal genes to induce the organizer

vertebrate development (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions