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Week 7 - 12 > Early Embryology > Flashcards

Early Embryology Flashcards

1
Q

Development of human being:

A 
Fertilisation
            |
Single cell
            |
Ball of cells
            |
Cavities + two layered disc
            |
Three layered disc with middle layer
            |
Segments in middle layer + tubes form from two outer layers
            |
Fully formed body
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2
Q

Where does fertilisation occur?

A

Ampulla of uterine tube within 12 hours of ovulation

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3
Q

What happens in fertilisation?

A

Reduction divisions (oocyte) completed

Restores diploid number of chromosomes (46)

Genetic sex determined

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4
Q

What type of cells are sperm and ovum?

A

Haploid (23 chromosomes)

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5
Q

What happened within 36 hours of fertilisation?

A

Initiation of cleavage

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6
Q

What essentially is the acrosome reaction?

A

Regulated exocytosis

Enables penetration of zona pellucida

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7
Q

How is acrosome reaction triggered?

A

Sperm penetrates corona radiata (hyaluronidase)

Interacts with ZP3 receptor

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8
Q

What happens during acrosome reaction?

A

Sperm digests zona pellucida

Sperm and oocyte membrane fusion

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9
Q

What happens after sperm fuses with oocyte?

A

Completion of oocyte meiosis

Release of nucleus into oocyte cytoplasm

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10
Q

What happens to prevent second entry of sperm into oocyte?

A

Cortical granules release content to degrade ZP3

Increase in oocyte membrane negative charge

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11
Q

What happens in 1st week of development?

A

Ovulation to implantation

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12
Q

What happens in donation of healthy mitochondria?

A

Parent’s nucleus removed and kept

Donor nucleus removed and destroyed

Parent’s nucleus placed inside donor egg

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13
Q

What happens to zona pellucida in first week of development?

A

Remains intact

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14
Q

Mitosis in first week of development:

A

Maternal and paternal chromosomes line up on spindle equator

Chromatids separate

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15
Q

What doesn’t happen in first week of development?

A

Cell growth - as only division in same volume

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16
Q

When does initiation of cleavage occur?

A

Within 36 hours of fertilisation

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17
Q

Early cleavage:

A

Cell division without growth (inside zona pellucida)

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18
Q

When does compaction cleavage begin?

A

At 8 cells - central cells linked by gap junctions

Become more like a homogenous ball

Anterior/posterior axis of embryo established

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19
Q

What’s a Morula?

A

16+ cells

Inner and outer layers

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20
Q

What happens to morula?

A

Transported along uterine tube to uterus

Zona pellucida disappears

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21
Q

What happens to outer cells on morula?

A

Divide to become trophectoderm (trophoblast) and inner cells (inner cell mass)

22
Q

What happens at 4.5 days?

A

Cavities form in inner cell mass

Blastocyst unattached to uterus

23
Q

What’s a blastocyst?

A

Trophoblast and inner cell mass

24
Q

What happens at 5-6 days in genetic testing?

A

Trophectoderm sampled

25
Q

What happens at 5.5 - 6 days?

A

Blastocyst binds to uterus epithelium

Embryonic pole attaches

26
Q

How does blastocyst bind to uterus wall?

A

Down regulation of anti-adhesion molecule MUC-1

Allows binding via selectins to glyco-compartments on epithelial cells (uterus)

27
Q

What molecules are involved in binding of blastocyst to uterine wall?

A

Integrins, laminin and fibronectin

28
Q

What happens at 6-7 days?

A

Implantation of blastocyst starts

29
Q

What happens during implantation of blastocyst?

A

Trophoblast becomes invasive

Scynctiotrophoblast multinucleate synctium invades via metalloproteases

30
Q

What does blastocyst implantation cause?

A

Immunosuppressive of host/graft and graft/host reactions

31
Q

What happens on day 8?

A

More embedding of blastocyst into uterine wall

32
Q

What happens to trophoblast on day 8?

A

Divides into synctiotrophoblast and cytotrophoblast

33
Q

What happens to embryo on day 8?

A

Two layers form - epiblast and hypoblast

Amniotic cavity (space)begins to form within epiblast.

34
Q

What coats blastocyst cavity?

A

Hypoblast cells - on day 9

35
Q

What becomes primary yolk sac?

A

Blastocyst cavity

36
Q

What happens on day 9?

A

Form primary yolk sac

Spaces develop within synctiotrophoblast

Formation of amniotic cavity

37
Q

What is formed deep to trophoblast following day 9?

A

Extraembryonic mesoderm

38
Q

Does the embryonic disc have layers?

A

Two layers

39
Q

What happens on days 11-12?

A

Blastocyst burrows completely into endometrium

Synctiotrophoblast cells erode through walls of large maternal capillaries

40
Q

What causes primitive placenta circulation?

A

Days 11-12

Synctiotrophoblast cells erode through large maternal capillary walls + bleed into spaces

41
Q

What new layer is formed in days 11-12?

A

Between yolk sac and cytotrophoblast

42
Q

What are spaces formed in, in days 11-12?

A

Extra embryonic mesoderm

43
Q

What’s the chronic in cavity formed by?

A

Fusion of spaces in extra embryonic mesoderm (days 11-12)

44
Q

What two layers develop in trophoblast at the end of week 2?

A

Synctiotrophoblast

Cytotrophoblast

45
Q

What 2 layers form in the inner cell mass at the end of week 2?

A

Epiblast - ectoderm

Hypoblast - endoderm

46
Q

What two cavities form at the end of week 2?

A

Amniotic cavity

Chorionic cavity

47
Q

What’s preeclampsia?

A

Features maternal hypertension and proteinuria after 20 weeks

48
Q

Where’s the most common site of ectopic pregnancy?

A

Ampulla - results in tube rupture + blood loss

49
Q

What environmental causes of malformations are there?

A

Drugs/chemicals

Infectious agents

Ionising radiation

50
Q

What determines dorsal-ventral axes in embryo?

A

Oocyte - but unclear mechanisms

51
Q

What determines left right axes in embryo?

A

Cilia movement (tend to be one direction) in node

52
Q

What axes are there in the embryo?

A

Dorsal-ventral

Left-right

Rostral caudal

Week 7 - 12 (38 decks)

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