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Body Logistics > 8 Embryology 1 > Flashcards

8 Embryology 1 Flashcards

1
Q

What are the 3 stages in embryology?

A

Pre-embryonic (week 1-2)
Embryonic (week 3-8)
Foetal (week 9-38)

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2
Q

How are pregnancy weeks calculated?

A

From date of last menstrual period so conception weeks +2, term is 40 pregnancy weeks

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3
Q

What happens in fertilisation?

A

Oocyte released from ovary
Travels along Fallopian tube
Fertilised by sperm in ampulla of Fallopian tube
Fertilised oocyte called zygote

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4
Q

What is the ideal site for implantation of the zygote?

A

Posterior uterine wall

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5
Q

What are the 4 stages in week 1?

A

Cleavage
Compaction
Hatching
Implantation begins

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6
Q

Describe what happens in cleavage

A

Formation of morula

  • first mitotic division
  • begins 30 hours after fertilisation
  • results in 2 blastomeres of equal size
  • zona pellucid forms - a glycoprotein shell
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7
Q

What kind of stem cells are in cleavage stage?

A

Totipotent (can become any cell)

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8
Q

Describe what happens in the compaction stage

A

Formation of blastocyst

  • formation of first cavity
  • now called a blastocyst
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9
Q

What type of stem cells are in compaction stage?

A

Pluripotent (can become one of many cell types)

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10
Q

What is the structure of a blastocyst?

A

Inner cell mass (embryoblast)
Trophoblast (surrounding layer of cells)
Blastocyst cavity (blastocoele)
Zona pellucida surrounds entire structure

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11
Q

Describe what happens in the hatching stage

A

Blastocysts hatches from zona pellucida

Can enlarge and interact with uterine surface to implant

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12
Q

What happens to the approximately 100 cells in conceptus?

A

8 will make embryo

Remainder develop into foetal membranes

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13
Q

What are the 2 main stages in week 2?

A

Differentiation

Implantation

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14
Q

Describe what happens in differentiation stage

A

2 distinct cellular layers emerge from outer cell mass and inner cell mass
Outer cell mass - syncytiotrophblast, cytotrophoblast
Inner cell mass - epiblast, hypoblast

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15
Q

What becomes the bilaminar disk?

A

Inner cell mass, made up of epiblast and hypoblast

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16
Q

Describe what happens in implantation

A

Uterine epithelium is breached, conceptus implants within uterine stroma
Established maternal blood flow within placenta
Establishes basic structural unit of maternal-foetal exchange

17
Q

What are the 2 main implantation defects?

A

Ectopic pregnancy

Placenta praevia

18
Q

What is an ectopic pregnancy?

A

Implantation at site other than uterine body (usually Fallopian tube)
Can be peritoneal or ovarian
Can become life-threatening emergency

19
Q

What is placenta praevia?

A

Implantation in lower uterine segment
Can cause haemorrhage
Require C-section delivery
Placenta partially or completely covers cervix

20
Q

What is the embryonic pole and when does it occur?

A

Rapid development of syncytiotrophoblast in week 2, day 9

21
Q

What is the abembryonic pole and when does it occur?

A

Primitive yolk sac formed in week 2, day 9

Yolk sac membrane in contact with cytotrophoblast layer

22
Q

What happens in week 2, day 11?

A

Primitive yolk sac membrane pushed away from cytotrophoblast layer by acellular extra embryonic reticulum
Reticulum later converted to extra embryonic mesoderm by cell migration

23
Q

What happens in week 2, day 12?

A

Maternal sinusoids invaded by syncytiotrophoblast
Lacunae continuous with sinusoids
Uteroplacental circulation begins

24
Q

What happens in week 2, day 13?

A

Formation of secondary yolk sac (definitive yolk sac) - pinches off from primitive yolk sac
Yolk sac bigger than amniotic cavity

25
Q

What happens in week 2, day 14?

A

Spaces within extraembryonic mesoderm merge to form chorionic cavity
Embryo and cavities suspended by connecting stalk - future umbilical cord
Bleeding could be confused with menstrual bleeding

26
Q

What is a blastocoele?

A

First cavity, formed as result of compaction

27
Q

What is the amniotic sac?

A

Formed from spaces within epiblast

28
Q

What is the primitive yolk sac?

A

Formed by hypoblast lining blastocoele

29
Q

What is the secondary yolk sac?

A

Formed within primitive yolk sac

30
Q

What is the extraembryonic coelem (chorionic cavity)?

A

Formed from spaces within extraembryonic reticulum and mesoderm

Body Logistics (20 decks)

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