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Mine ESA 1 > Early Embryonic Development > Flashcards

Early Embryonic Development Flashcards

1
Q

When is the pre-embryonic period?

A

weeks 1 + 2

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2
Q

When is the embryonic period?

A

weeks 3 - 8

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3
Q

When is the fetal period?

A

weeks 9 to term

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4
Q

How many weeks are there in total in a pregnancy?

A

38 weeks

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5
Q

Where is the oocyte fertilised?

A

In the ampulla of the fallopian tube

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6
Q

What is the name given to a fertilised oocyte?

A

Zygote

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7
Q

Define a zygote

A

A single cell product of fertilisation of an ovum by a sperm produced by fusion of male and female pro nuclei

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8
Q

Define cleavage and when does it occur?

A

Dividing of cells into two masses called blastomeres, it is the first mitotic division, day 2

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9
Q

What is the morula a result of?

A

The cleavage of the fertilised ooycte

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10
Q

What are the cells in the morula?

A

Totipotent (they have the ability to form any cell type)

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11
Q

What occurs to form a blastocyst?

A

Compaction which occurs on day 4 giving us the first cavity the bastocyst cavity

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12
Q

What is the name given to the glycoprotein shell prevnting polyspermy?

A

Zona pellucida

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13
Q

What does hatching from the zona pellicuda allow the blastocyst to do?

A

It allows it to enlarger and can interact with uterine surface to implant

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14
Q

When does implantation begin?

A

Day 6/7

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15
Q

Where is the ideal side for implantation?

A

The posterior uterine wall

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16
Q

An ectopic pregnancy occurs when?

A

Implantation doesn’t occur inside the uterine cavity, the most common site for this is the fallopian tubes = medical emergency

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17
Q

What is placenta pravia?

A

This is when implantation occurs at the lower uterine segment so the placenta grows across the cervical opening. This requires a c-section delivery

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18
Q

Differentiation occurs at the start of week 2 giving us what?

A

An outer cell mass : trophoblast

A inner cell mass: embryoblast

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19
Q

The trophoblast becomes….

A

the cytotrophoblast and the the synctiotrophoblast

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20
Q

The embroyblast becomes…

A

the epiblast and hypoblast = bilamner disc

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21
Q

At day 9 at the embryonic pole and abermbroynic pole?

A

Embryonic pole -> rapid development of synctioctrophoblast

Abembryonic pole -> primitve yolk sac formed

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22
Q

At day 11?

A

The primitive yolk sac is pushed away from the cytotorphoblast by acellular extraembryonic reticulum

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23
Q

At day 12?

A
  • Maternal sinosoids are invaded by synchiotrophoblasts
  • lacunae become continous with sinosoids
  • uteroplacental circualtion begins
  • uterine stroma prepares for support of embryo
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24
Q

Day 13?

A

Formation of secondary yolk sac as it pinches off from primary yolk sac

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25
Q

What does the acellular extraembryonic reticulum become?

A

extraembryonic mesoderm

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26
Q

Day 14?

A

Sees:

  • the formation of the chronic cavity formed by spaces in the extraembryonic mesoderm merging
  • embryo and its cavities are suspended by the conencting stalk
27
Q

When is it that you can get bleeding which can be confused with the menstrual cycle?

A

Day 14 as the access to glands and vessels is complete hence bleeding. A fibrin plug will heal up the breach.

28
Q

What is the bilamner disc?

A

the two layer embryonic disc consisting of an epiblast and a hypoblast, it is derived from the embroyblast

29
Q

What is a germ layer?

A

It is one of the primary tissue layers that make up the trilaminar disc: ectoderm, mesoderm and endoderm.

30
Q

What is the ectoderm?

A

It is the outermost layer of cells dervied from the three embryonic germ layers.

31
Q

What is the endoderm?

A

The innermost layer of the three embryonic germ layers formed during gastrulation

32
Q

Describe what a dorsal surface is?

A

The outermost surface during early development.

dorsal = back

33
Q

Describe what a ventral surface is?

A

The inner most surface during early development

34
Q

What is the mesoderm?

A

the middle layer of the three embryonic germ layers of the trilaminer disc

35
Q

Where does the primitve streak begin?

A

At the caudal end of the bilmaner disc where there is a thickned region of epiblast.

36
Q

What is gastrulation?

A

The process occuring in the 3rd week of development resulting in the formation of 3 germ layers of the trilamner disc from epiblast migrating through the primitve streak?

37
Q

What produces the trilamner disc?

A

gastrulation

38
Q

Ectoderm becomes…

A

Organs and structures that maintain contact with the outside world

39
Q

Give some examples of surface bits that the ectoderm becomes

A

skin, hair, nails, lens of eye, cornea of eye, mouth and anus lining

40
Q

Give some examples of neural bits that the ectoderm becomes

A

brain, spinal chord, peripheral nerves, retina and iris of eye.

41
Q

Mesoderm becomes..

A

Supporting tissues

42
Q

Since mesoderm becomes supportive tissues give examples of these

A

CT, bone, cartilage, smoooth muscle, skeletal muscle, cardiac muscle, blood, blood vessels, urinary system

43
Q

Endoderm becomes….

A

Internal structures

44
Q

Give some examples of internal structures that the endoderm becomes

A

lining of GI tract, lungs, glands associated with digestion, epithelia

45
Q

What three cavities are present at week 3?

A

amniotic cavity
yolk sac
chronic cavity

46
Q

On which side of the epiblast does the primitive streak appear?

A

dorsal

47
Q

Where is the primitive node located?

A

At the cranial end of the streak

48
Q

Where is the primitive pit located

A

At the centre of the primitive node

49
Q

Which was does gastrulation proceed?

A

cranial to caudal i.e. cephalocaudally

50
Q

When does migration and invagiantion complete?

A

week 4

51
Q

Describe gastrulation

A
  1. cells on the epiblast migrate towards the primitive streak
  2. They ivaginate into epiblast and displace the hypoblast -> mesoderm
  3. As more cells migrate through streak laterally and cephalod -> head
  4. Mesoderm spreads out between ectoderm and endoderm like a sandwhich filinf but leaves 2 holes: mouth and anus
52
Q

What is the notochord?

A

It is the solid rod of cells formed in the midline from epiblast cells migrating forward through the primitive node of the primitive streak until they reach the prochordal plate

53
Q

What is the significance of the notochord?

A
  • defined the phylum chordata
  • defined midline
  • sets basis for axial skeleton which forms around it
  • drives neurlation (formation of the nervous system)
54
Q

What is the notochord in adults?

A

It regresses and forms the nucleus pulposus of intervertebral discs.

55
Q

What is the clinical significance of the notochord in later life?

A

As it forms the nucleus pulposus which is the prolapsed material that protrudes posterior laterally causing pressure on associated spinal nerves leading to parasthesia, back pain or paralysis -> slipped disc

56
Q

Monozygote twins?

A

Are twins where 1 zygote has formed 1 infant

57
Q

What is the name given to twins from 2 zygotes?

A

dizygote twins

58
Q

If the embryo splits after the 2nd clevage?

A

the twins get their own placenta

59
Q

If the inner cell mass/embryoblast duplicates?

A

the twins have their own placenta but the same amniotic sac

60
Q

If the primitive streak duplicates?

A

The twins have their own placenta and amniotic sac

61
Q

What is the name given to the genes that can be disrupted by certain substances during pregnancy?

A

Teratogenes

62
Q

Why does the primitive streak define anterior and posterior?

A

because it appears at the end of the bilaminer disc

63
Q

What does the primitive node ensure?

A

ensures correct dorsal-ventral and left-right development.

64
Q

What is the condition when the visceria are mirror images?

A

situs inversus

Mine ESA 1 (7 decks)

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