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Biology > Preimplantation of embyo > Flashcards

Preimplantation of embyo Flashcards

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1
Q

If its a mammal, embryo implants

Whats so significant about it

A
  • Blastomere division is not synchronous (not at same time)
  • Mitosis is slow
  • there is compaction stage
  • Blastula= blastocyst
  • Blastocyst hatches then implants
  • Regulative development ( No morphogens)
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2
Q

What type of eggs are mammalian eggs compared to frog eggs

A

Isolecithal- even distribution of yolk

Frog eggs are telolecithal ( vegetal pole more yolk than animal)

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3
Q

What type of cleavage does mammals do

A

Holoblastic= full cleaavage of egg and yolk (like frogs)

Cleavage is rotational, asynchronous, 24 hours per cycle.

1st cleavge=meridional
2nd= meridional and the other equatorially

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4
Q

What is the first morphological event in the preimplantation development

A

COMPACTION

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5
Q

What is compaction

A

Transfoms embryo to loose cluster of cells to tight packed mass
Blastomeres start to look different here from each other

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6
Q

With compaction , what else is established

A

Intracellular polarization

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7
Q

What does polarization involve

A

Some peripheral cells make 1 polarized and 1 non polarized cell

NON POL= forms inner cell mass-embryo
POL= stays at periphery and becomes trophoectoderm

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8
Q

Why is trophoectoderm important? what do they dfferentiate into

A

Differentiate into large trophoblasts for the placenta

Imp for hatching and cavitation of blastocyst

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9
Q

What do the polar/mural trophoectoderm cells do

A

polar-contact the inner cell mass and proliferate
Mural- surrounds blastocoel and differentiates into large trophoblast cells

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10
Q

Why are trophoectoderm polyploid

A

endoreplication - replication with no mitosis

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11
Q

How does cavitation occur (64 cell stage)

A
  • intracellular vaculoles appear first
  • Eventually these r drained into inner cell mass the forms blastocoel
  • For fluid to accumulate you need tight sealed trophoectoderm layer- sealing done by non contrac=tile actin rings- expands to reach tight junctions and adherens
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12
Q

What is involved in blastocyst hatching

A

Blastocyst expnads due to liquid accumulation in blastocoel

When burst, it becomes free of the zona pellucida

5-6th day

NOW IT CAN IMPLANT

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13
Q

What are zona breaker cells

A

speazilied trophovblast cells that have secretory vesicles to open the zona pellucida

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14
Q

Where does embryo implant

A

Endometrium

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15
Q

At implantation, what does the trophoectoderm produce

A

Chorion

Forms vili and makes maternal pacenta nutrion

Produce hormones

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16
Q

WHat if implantation ocurrs at the wrong place

A

Ectopic pregnancy

Zona pellucida normally prevents embryo attaching to wall of fallopian tube but this could go wrong

17
Q

Other than zygote what else can initiate embyonic development

A

blastomeres are totipotent
Until mitosis promoting factors start

18
Q

What can totipotent cells turn into that pluripotent cannot

A

extraembryonic tissue like placenta

19
Q

OOplasmic segregation vs signal transdiction

A

OOplasmic is intrinsic with morphogens

transduction is extrinsic= signal interacts with receptor, sends cascade (second messengers) to nucleus and influence transcription factors for gene expression

20
Q

What are the benefits of regulative development

A

DOES NOT DEPEND ON MORPHOGESN

DEPENDS ON INTERACTIONS WITH O|THER CELLS

21
Q

What is eveidence of regulation

A

Identical twins

22
Q

More than 1 embryo leads to twins. But always may not

A

Chimera

The 2 blastocysts fuse and form chimeric embryo

Can have diff sex organs, bloody types etc

23
Q

MECHANISM OF PREIMPLANTATION

A
  • 16 cell stage= morula
  • Blastocyst forms, then blastocoel (64 cells)
  • From peripheral cells forms:
    Inner cells= inner cell mass of pluriopoitent cells
    Peripheral cells=trophoectoderm differentiates into
    trophoblast cells
  • Accumulation of fluid in blastocoel then bursting = hatching
    free of ZP (6th day)
  • Polar trophoectoderm= proliferate
    Mural trophoectoderm= differentiate into trophoblast cells
  • Implantation with trophoectoderm makes chorion, develops villi for feto maternal interactions and produces hormones

Biology (36 decks)

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