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Developmental > Lecture 3: Gastrulation > Flashcards

Lecture 3: Gastrulation Flashcards

The formation of the first three tissue layers

1
Q

Rostral = cranial

A

head end

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2
Q

caudal

A

tail end

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3
Q

dorsal

A

top of the animal

we allocate left and right

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4
Q

ventral

A

abdominal side

anterior

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5
Q

anterior

A

side of the face

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6
Q

posterior

A

opposite of posterior so in animal same as dorsal

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7
Q

proximal and distal

A

for describing limbs

proximal is close to the body

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8
Q

gastrulation in drosophila

A

ventral furrow formation = a slit = opening to the blastula

blastopore

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9
Q

gastrulation in sea urchins

A

deuterstomes
not symmetrical to juveniles
invagination
round blastopore

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10
Q

invagination

A

where cells are released from and 3 distinct germ layers can separate out = an opening to the inside
will eventually become anus

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11
Q

gastrulation

A

site is the blastopore/primative streak
formation of first embryonic tissue layers through morphogenetic movements - shape creating from epiblast/primitive ectoderm

  1. definitive ectoderm = sole source of nervous system
  2. mesoderm = majority of inner organs + blood, muscle kidney + gonads definitive endoderm

from epiblast
and in aminotes hypoblast = primative endoderm extraembryonic

evolved in ALL bilaterians

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12
Q

gastrulation in xenopus frog

A

deutrestomes
blastopore
round blastopore with a yolk plug in the middle

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13
Q

gastrulation in chicken

A

slit blastopore - primitive streak (forms on one side of blastula)
initially short and wide and then extends with cells ingressing at the edges of the slit towards the primative steak = 2mm long under stereo microscope

epiblast - tightly packed cells
or primative ectoderm - cells that undergo EMT and spread underneath
cells leave the epiblast through an EMT
groove - so many cells engaged = end up with.a depression
mesoderm
endoderm

epiblast produces the mesoderm and endoderm and what stays on the outside will become the definitive ectoderm

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14
Q

how do cells in the epiblast move

A 
invagination 
involution
ingression
delamination
epiboly (growth of cells around the yolk) and a combination towards the blastopore/primitive streak

detach from epiblast and spread underneath to for 2 inner tissue layers mesoderm and endoderm
remainder of the epiblast becomes the ectoderm

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15
Q

gastrulation in humans

A

implantation:
blastocysts consists of inner cell mass

from which hypoblast forms
amnion
epiblast forms a primitive streak from which cells emigrate

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16
Q

but in mice n rodents developmental anatomy distinct:

A

primitive streak starts at caudal end
cells detach and spread
endoderm and mesoderm are on the outside
ectoderm on the inside

gastrula inside out initially

17
Q

the fate of ecto endo and mesoderm

A
  1. zygote
  2. blastula
  3. gastrula
    A = germ cells
    B = ectoderm
    central nervous system and epiermal layer of skin and pigment cells

vertebrates - cells that can migrate away and form peripheral system

endo
digestive tube gut canal
thyroid cells -pharynx
alveolar cell

mesoderm
tubule cells of kidney
notocord
facial muscle
red blood cells
bone tissue
18
Q

time and rostrocaudal (anterior-postrior) (head-tail)position of cells in the streak vs. mediolateral position in the germ layers (close to the node/orsal blastompore vs away from it

A

cels gasturalting

early = rostral anterior

later - caudual posterior

rostral streak = medial = dorsal once the body wall is closed ventrally

caudal streak = lateral = ventral

medio lateral axis = dorso-ventral axis = back abdomen

19
Q

left right axis

A

insitu hybridsation
symmetry is broken
Shh gene
Pitx2

let right as viewd from the top dorsal side

20
Q

how the germ layers and the longitudinal body axis is formed

A

conc:
the fate of the dorsal blastopore lip is to make axial mesoderm notochord

the graft induces the formation of the 3 germ layers and organises the formation of the 3 body axis

21
Q

how does the organiser form

A

dorsal blasta animal cap cells = ectoderm
middle = mesoderm
ventral blasta vegetal cells = endoderm

when ventral dorsal tissues are co cultured the dorsal tissue is converted to mesoderm

Sox17 endoderm developmental path
vegT - notal genes

endoderm

mRNA for VegT are in the endodermal part of the egg

when translated vgT protein activates TGF beta signalling inform of nodal which signals to the marginal zone

translation of veg1/Gdf1 will raise tgf beta levels
translation of wind components stabilisers beta catenin
activate nodal genes

= nodal and tgf signalling from vegetal pole signals to the marginal cells = induced mesoderm
high = organiser will be induced in marginal zone + expressed inhibitors

high BMP = lateral or ventral mesoderm
absence of BMP
the dorsal

high wnt8 determines caudal or tail end
absence of wnt8 determines rostral or head end of longitudinal body axis

transcription factors:
VegT, B-catenin
secreted = organiser, nodal vg1/Gdf1, BMP, Xwnt8

22
Q

gastrulation in vertebrates

A

early cleavage organisation how the embryo deals with the yolk differs

all vertebrates develop an organiser

23
Q

tail bud

A

cells gather at tail bud drives formation of sacral and caudal part of body axis
defects in gastrulation are not compatible with life
defects in tail bud development lead to posterior body truncations
defects in gastrulation arise from loss, defects in tail bud formation from the partial loss of function of organiser genes

24
Q

Niewkoop centre in frogs

A

in vegetal zone high nodal signalling and beta catenin
the rganiser will be induced in the marginal zone
overlap in the marginal zone and vegetal zone

25
Q

what is difference between the normal mitotic cell cycle and first zygotic cell cycle

A

g1 and g2 are omitted

26
Q

what are structures that are shared between vertebrates

A

somites

hindbrain consisting of individual rhombomeres segmented

27
Q

the role of BMP

A

depending of how much yolk you have
frog = embryo wrapped around yolk rich cells at the vegetal cells

or flat ontop of yollk
midline = primitive streak
the further they are the more lateral or on the side they are

in the middle due to organiser high level of BMP inhibitors expression
could be soluble and travel a distance or can be autonomously and work in the cell
the cells in the midline get the BMP pathway shut off
the cells further away from the midline less and less BMP signalling

cells in the ectoderm through BMP become epidermis cells
mesdoerm = lateral or extraembryonic mesoderm in mice

in frog what was lateral becomes venral
dorsal = midline
ventral= far away

in chicken
once the endoderm closes and forms gut canal - same

midline becomes dorsal
what was out and lateral becomes ventral

Developmental (12 decks)

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