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Embryology > Early Embryonic Development II > Flashcards

Early Embryonic Development II Flashcards

1
Q

3 Functions of Zona Pellucida?

A
  1. Protect the pre-implantation embryo from muscular contracitons of the oviduct
  2. Aid in eventual breakdown of itself by storing proteases
  3. Protection from infection
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2
Q

Why cant Bovine Viral Diarrhea affect early embryo?

A

Most likely due to the blocking of zona pellucida

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3
Q

What is required to break down zona pellucida?

A

Proteases

e.g. strypsin

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4
Q

What are the 3 axes

A

Anteror-posterior (craniocaudal)

Dorsoventral

Right-left

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5
Q

What is the hypoblast?

A

Flattened cells facing blastocyst cavity

Form a cell sheet that lines epiblast

Epithelium

Eventually forms part of yolk sac

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6
Q

What is essential for hypoblast development?

A

GATA-6 Expression

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7
Q

What is epiblast?

A

Remaining cells of the ICM that are multilayered

Eventually form embryo

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8
Q

What is essential for epiblast development?

A

Nanog expression

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9
Q

What is Rauber’s layer?

A

Trophectoderm cells overlying the epiblast

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10
Q

Formation of embryonic disc

A

THe Rauber’s layer disintegrates and leaves the epiblast exposed

Epiblast becomes ovoid structure

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11
Q

What are the 2 groups of mammals in terms of development within the uterus and implantation

A

Pre-attachment period within the uterus is long (several weeks) - domestic animals

Blastocyst implants quickly after entering uterus (primates)

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12
Q

How do horses, carnivores and primates differ from ruminants and pigs durring expansion?

A

Ruminants and pig the blastocyst becomes tubular then filamentous

In horses, carnivores and primates, the blastocyst remains spherical and does not elongate

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13
Q

What is histotrophe?

A

Secretory products of the endometrial glands

  • Enzymes
  • Growth Factor
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14
Q

What occurs to allow for maximum production of histotrophe?

A

Endometrial glands undergo substantial hyperplasia and hypertrophy during gestation to increase surface area for maximum production of histotrophe

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15
Q

What does histotophe do?

A

Nourish the embryo during pre-implantataion period

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16
Q

What must be prevented in order for the early events of embryogenesis to continue into an established pregnancy?

A

Luteolysis must be prevented

17
Q

What is luteolysis?

A

Breakdown or loss of the corpus luteum

18
Q

What are the two forms that recognition signalling from conceptus to maternal system?

A

Luteotrophic

Anti-luteolytic

19
Q

What is luteotrophic?

A

A hormone(s) to act on the corpus luteum to maintain luteal function

20
Q

What is anti-luteolytic

A

A hormone(s) to prevent utereine release of luteolytic-promoting substances such as prostaglandin (F2-alpha)

21
Q

Two function of IFN Tau?

A

Acts on endometrial cells of uterus and inhibits oxytocin receptor production - Oxytocin cannot now stimulate PGF2alpha synthesis

Increases secretion of proteins from endometrial glands which enter lumen and nourish the embryo

22
Q

What is function of estradiol in pregnant sow?

A

Re-routes PGF2alpha to uterine lumen where it is destroyed - preventing luteolysis

23
Q

What is trans-uterine migration of equine conceptus?

A

During pre-attachment phase, horse conceptus is moved over the endometrial surface by uterine contractions

PGF2alpha is significantly reduced

24
Q

5 phases of implantation

A

Phase 1 - Shedding of ZP

Phase 2 - Pre-contact period when blastocysts can migrate and undergo orientation without contact with epithelia, initiate pregnancy recognition signalling

Phase 3 - Trophectoderm associates with endometrial epithelium for unstable adhesion. In ruminants initial development of microvilli begins

Phase 4 - Trophectoderm firmly adheres to luminal epithelium and in some species superficial glandular epithelium

Phase 5 - Unique to species with invasive implantation of blastocyst through uterine luminal epithelium into uterine stroma that becomes decidualized

25
Q

Which phase does initiation of pregnancy signal occur?

A

Phase 2

26
Q

What occurs for ruminants in phase 3?

A

Initial development of microvilli begins

27
Q

What species stop at phase 4?

A

Domestic animals

Cows and so on

28
Q

What species undergo phase 5 of implantation?

A

Primates

Carnivores

29
Q

Which species has longest time from ovulation does implantation occur?

A

Horse 17-56

30
Q

Which species has shortest time from ovulation of implantation?

A

Rodents

31
Q

Four forms of implantation?

A

Antimesometrium implantation

Mesometrium Implantation

Eccentric Implantation

Centric Implantation

32
Q

What occurs durring antimesometrium and mesometrium implantation

A

Blastocyst invades the uterine epithelium and into the unterine stroma where the embryo will develop

  • Primates and Guineapigs
33
Q

What occurs in ecentric implantation?

A

Blastocyst gets lodged in a uterine fold or cleft and the uterine mucosa around it proliferates

  • Rodents
34
Q

What occurs in centric implantation?

A

The fluid filled sacs around the embryo become tightly associated or apposed to the uterine epithelium and attach

  • Horse , cattle , sheep , pigs , dogs . cats . rabbits
35
Q

What is Diapause?

A

Blastocyst can enter a period of decreased cell division and metabolic inactivity and ususally delayed blastocyst implantation

36
Q

Benefit of seasonal delayed implantation?

A

Increase probability that offspring are born at a favorable time of yr for optimal survival

37
Q

Two types of Diapause?

A

Seasonal delayed implantation

Falculative or Lactational dely implantation

38
Q

Benifit of faculative or lactational delayed implantation?

A

Since rodents can become pregnant during post-partum estrus while still feeding pups, implantation can be delayed until weaning is complete to prevent the mother from having to support two litters at the same time

Embryology (25 decks)

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