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E: Human Morphogenesis and Embryologically > Blastocyst > Flashcards

Blastocyst Flashcards

1
Q

What are the 3 lineages for a mature blastocyst?

A
  1. Epiblast
  2. Trophopblast
  3. Hypoblast
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2
Q

Epiblast?

A

Cells of the inner cell mass

Develop into the embryo proper

Pluripotent

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3
Q

Trophoblast?

A

The outer cell

Give rise to the trophetoderm

Syncytio-trophoblast

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4
Q

Hypoblast?

A

Derives from the inner cell mass

Distinct from the epiblast

Extra-embryonic endoderm recursors

Give rise to the yok sac.

AS18

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5
Q

What happens during day 8?

A

The blastocyst is partially embedded in the endometrial stoma.

The trophoblast has differenetiated into its two layers.

Cell in the cytotrophoblast divide and migrat into the syncytiotrophoblast (losing their cell membranes).

Cells in the ICM differentiate.

A small cavity appears within the epiblast.

The blastocyst will penetrate the wall of the uterus and implant into the uterine mucosa.

See AS19

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6
Q

Aminoblasts?

A

Epiblast cells adjacent to the cytotrophoblast

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7
Q

What does the trophoblast differentiate into two layers?

A

Cytotrophoblast: inner layer of mononucleated cells.

Syncytio-trophoblast: outer multinucleated zone without distict cell boundaries.

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8
Q

Name the two cell types the inner cell mass differentiate into?

A

Hypoblast: a layer of small cuboidal cells adjacent to the blastocyst cavity.

Epiblast: a layer of high columar cells adjacent to the amniotic cavity

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9
Q

What happens during day 9?

A

Blastocst is more deeply embedded into the endometrium.

The penetration defect in the surface epithelium is closed by a fibrin coagulum.

Vascuoles appear in the syncytrium- when they fuse form a large lacunae called trophoblastic lacunae.

Flattened cells (originating from the hypoblast) form a thin membrane called the exocoelomic membrane.

This membrane and the hypoblast, from the lining of the primitive yolk sac (or exocoelomic cavity)

See AS20

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10
Q

What happens during day 11/12?

AS21

A

Blastocyst is completely embedded in the endometrial stroma.

Produces a slight protrusion into the lumen of the uterus.

Cells of the syncytiotrophoblast penetrate deeper into the stroma and erode the endothelial lining of the maternal capillaries (known as sinusoids).

Maternal blood enter the lacunar system.

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11
Q

Graphical representation of the fate decisions for totipotent blastomeres?

A

See additional sheet 22

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12
Q

Name the 3 cell types from the blastocyst?

A
  1. Epiblast cells (ES)
  2. Trophoectoderm (TS)
  3. Primitive endoderm (XEN)

All have different growth requirements.

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13
Q

Embryonic stem cells?

A

Derived from ICM.

Immortal- does not die after a few cell divisions.

Pluripotent- can give rise to all the cell types that make up the body.

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14
Q

Teratomas

A

Contain derivatives of all germ layers

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15
Q

Chimeras?

A

Cells colonise all 3 germ layers

Can contribute to the germ line

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16
Q

A test that can be conducted that is evidence the ES cells are truly pluripotent?

A

Dye the cells (blue)

Electrofusion: only outside cells survive as a tet)raploid.

Add with another dyed (red) ES cells.

See that the blue cells become the placenta and the red cells become the whole embryo

17
Q

Name the 4 factors that influence the ES cell phenotype?

A
  1. Culture conditions- signalling
  2. Developmental stage- once fate decides cannot go back.
  3. Species difference
  4. Heterogenous- fluid state
18
Q

Name the effects of the non-destructive derivation methods?

A

Derived ES cells from blastomere outgrowth.

Avoid need to destroy embryo

19
Q

TS cells?

A

Contribute to the development of extra-embryonic tissue eg. placenta.

When differentiated become large cells called trophoblast giant cells.

Contribution in chimera-self renewal.

20
Q

XEN cells differentiation into?

A

parietal endoderm

Visceral endoderm

See additional sheet 23

21
Q

Name the 6 forms of XEN cells morphology?

A
  1. Rounded with numerous villi.
  2. Epithelial-like with numerous villi
  3. Short pseudopodium
  4. Colony where one cell is extending several pseudopodia.
  5. Curved psuedopodium.
  6. Behave similar to embryonic
22
Q

How many active X’s do naive ES cells retain?

A

2 active X

23
Q

How is one X inactivated?

A

Differentiated ES randomly inactivate one X

24
Q

TS cells inactivate what X?

A

The paternal X

25
Q

XEN cells inactivate what X?

A

Inactivate paternal X

26
Q

What are the names given to the two X’s?

A

Paternal: from the male

Maternal: from the female

27
Q

why is it the paternal X is inactivated in both TS and XEN cells?

A

maternal child conflict.

Males can mate with many females (therefore they have a higher chance of protecting its genes)

While a mother has to protect herself so she can have more children therefore the males (paternal) X is inactivated

E: Human Morphogenesis and Embryologically (15 decks)

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