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Vertebrate development > Extraembryonic membranes > Flashcards

Extraembryonic membranes Flashcards

1
Q

Extraembyronic membranes aren’t merely membranes, they’re…?

A

Organs

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2
Q

What is the main stage of each day in development?

A
  1. Fertilisation
  2. Cleavage
  3. Compaction
  4. Differentiation
  5. Cavitation
  6. Zona hatching
  7. Implantation
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3
Q

Which TFs are used for the 1st cell fate decision?

A

TE
= Cdx2

ICM
= Nanog + Gata6

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4
Q

Which TFs are used for the 2nd cell fate decision

- of ICM?

A

EPI
= Nanog

Primitive endoderm
= Gata6

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5
Q

Why do we have extra embryonic membranes?

A

Any animal w/ shell-less egg remains tied to water

  • due to previous aquatic stages being maintained
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6
Q

Amniotes

A

= Clade of tetrapods

  • contains reptiles, birds + mammals
  • all have amniotic eggs + internal fertilisation
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7
Q

Amniotic egg

- what is it?

A

Series of fluid filled membranes

  • enabled 1st land animals to lay eggs on dry land (freed reptiles of need to return to water to reproduce)
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8
Q

Extra-embryonic tissue

- define

A

= embryo-derived tissue that won’t be part of embryo

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9
Q

The 4 extra-embryonic membranes in all amniotes

A

Amnion
Allantois
Chorion
Yolk sac

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10
Q

Additional extra embryonic membrane in vertebrates

A

Placenta

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11
Q

Extraembryonic membranes

- define

A

Membranes surrounding embryo

Present in some invertebrates and all vertebrates

Ensure embryo protection from injury

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12
Q

Yolk sac

A

1st element in gestational sac

Important in early embryonic blood supply

Most of it incorporated into primordial gut during 4th week of development

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13
Q

Amniotic cavity formation

- cell layers involved

A

EPI layer

Endoderm later of yolk sac + gastrointestinal tract

Extraembryonic mesoderm + mesoderm

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14
Q

Yolk sac

- 4 weeks

A

Connected to primitive digestive system

-> yolk sac contributes nutrients to embryo

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15
Q

Endoderm

-forms..?

A

GI tract
Yolk sac
Allantois

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16
Q

Yolk sac

- attachment in humans

A

attaches to outside of developing embryo + connect to umbilical cord via yolk stalk

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17
Q

Yolk sac

- function

A
  • provide nutrients in reptiles + birds
  • forms intestine side branch in mammals
  • preliminary circulatory system (delivers nutrients via primitive aorta)
  • primitive erythroid cells emerge from yolk sac blood islands
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18
Q

yolk sac
- structure?

  • eventually absorbed by?
A

Extraembryonic endoderm
+ mesoderm

Into the gut of the embryo

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19
Q

Allantois

- function

A

Reptiles + birds
= N waste reservoir

Takes part in placenta formation

Develops as side branch to bladder

20
Q

Allantois

- in human over development

A

Size of allantois decreases
-> becomes elongated sac + part of umbilical cord

Blood vessels of allantois develop into umbilical cord blood vessels

Allantois later becomes the urachus
= removes N waste from foetal bladder

21
Q

Urachal disorders

  • how do they occur?
  • effects?
A

Abnormalities w/ sealing of the channel during foetal development

Asymptomatic
Urachal Cysts can become infected

22
Q 
Amniotic cavity (amnion)
- what is it?
A

Closed sac between embryo + amnion

Contains amniotic fluid

23
Q

Amniotic cavity

- structure

A

Lined w/ ectoderm

Covered w/ extra embryonic mesoderm

24
Q

Amniotic sac

- formation

A

Week 3-4
Folding of embryonic disc
-> draws amniotic membrane ventrally over embryo
-> enclosing of embryo in amniotic sac

25
Q

Amniotic fluid

  • circulated by?
  • removed by?
  • Low Mg+ levels associated with?
A

Foetal inhaling + swallowing

Foetal exhalation + urination

Preeclampsia + diabetes

26
Q

Amniotic fluid

- what is it?

A

Medium containing proteins, lipids, urea + electrolytes actively secreted by cells lining amniotic cavity

27
Q

Amniotic fluid

- early gestation

A

AF volume increases by getting water from mother’ plasma + transporting it to foetus via foetal membranes

28
Q

Amniotic fluid

- week 8-10 gestation

A

Skin not keratinised

-> .:. bidirectional fluid diffusion between foetus + AF

29
Q

Amniotic fluid

- 28 week gestation

A

AF increases to max volume

30
Q

Amniotic fluid

- foetal nutrition

A

Not main source
(15% of nutrients)

BUT important for development + maturation of gut

31
Q

Amniotic fluid

- components

A

Amino acids
Proteins
Hormones
GFs (EGF, Interleukin etc)

32
Q

Amniotic fluid stem cells (AFS)

A

Show some features of pluripotency

Able to differentiate into cells of all 3 germ layers

33
Q

Chorionic cavity

- structure

A

Lined w/ extra embryonic mesoderm

Covered in trophoblast cells forming vili

34
Q

Chorionic cavity

- what is it?

A

Transient fluid-filled space lost by expansion of amniotic sac
- which finally fuses to chorionic membrane

35
Q

Differences between amnion + chorion

A 
A = sac that cover embryo
C = surrounds amnion 
A = absent in amphibians + fish 
C = present
A = ectoderm + ExE mesoderm 
C = formed by TE + mesoderm
36
Q

Chorionic Villi

- what are they?

A

Act like barrier between maternal blood + foetal blood

- exchanges occur through vili walls

37
Q

Chorionic villi

- formation

A

Offshoots from surface of trophoblast

38
Q

Allantois

- formation

A

Outgrowth from hindgut which pushes its way into extra embryonic coelom

39
Q

Chorion

- function

A

Acts as extra embryonic lung (exchange of gases)

Develops into placenta
- important in respiration, excretion + nutrition

40
Q

Amnion

- function

A

Protects embryo from injury

Amniotic fluid absorbs shock + prevents desiccation of embryo

41
Q

Placenta

- blood circulation

A

Maternal blood in intervillous space constantly in circulation

Arteries + vein open into roof of cotyledon
-> blood pressure drives blood to foetal end of intervillous space

42
Q

Placenta

- functions

A 
Acts as lungs, 
kidneys 
liver 
GI system
Endocrine system 
Immune system

Produces hormones to maintain pregnancy

Protects foetus from mother’s IS

43
Q

Placental lactogen

- what is it?

A

= hormone

- modifies metabolic state of mother during pregnancy to facilitate energy supply of the foetus

44
Q

Placental lactogen + Prolactin

- what does it effect?

A

Placenta development

Altered glucose metabolism

Breast development

Maternal behaviour

45
Q

Prolactin

- what is it?

A

Hormone that activates breast milk production

46
Q

Placenta

- What can go wrong?

A

Amniotic bands

  • can contract around fingers + limbs
  • 1/1200 live births

Vertebrate development (12 decks)

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