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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
What does the acellular extraembryonic reticulum become?
extraembryonic mesoderm
26
Day 14?
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
When is it that you can get bleeding which can be confused with the menstrual cycle?
Day 14 as the access to glands and vessels is complete hence bleeding. A fibrin plug will heal up the breach.
28
What is the bilamner disc?
the two layer embryonic disc consisting of an epiblast and a hypoblast, it is derived from the embroyblast
29
What is a germ layer?
It is one of the primary tissue layers that make up the trilaminar disc: ectoderm, mesoderm and endoderm.
30
What is the ectoderm?
It is the outermost layer of cells dervied from the three embryonic germ layers.
31
What is the endoderm?
The innermost layer of the three embryonic germ layers formed during gastrulation
32
Describe what a dorsal surface is?
The outermost surface during early development. | dorsal = back
33
Describe what a ventral surface is?
The inner most surface during early development
34
What is the mesoderm?
the middle layer of the three embryonic germ layers of the trilaminer disc
35
Where does the primitve streak begin?
At the caudal end of the bilmaner disc where there is a thickned region of epiblast.
36
What is gastrulation?
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
What produces the trilamner disc?
gastrulation
38
Ectoderm becomes...
Organs and structures that maintain contact with the outside world
39
Give some examples of surface bits that the ectoderm becomes
skin, hair, nails, lens of eye, cornea of eye, mouth and anus lining
40
Give some examples of neural bits that the ectoderm becomes
brain, spinal chord, peripheral nerves, retina and iris of eye.
41
Mesoderm becomes..
Supporting tissues
42
Since mesoderm becomes supportive tissues give examples of these
CT, bone, cartilage, smoooth muscle, skeletal muscle, cardiac muscle, blood, blood vessels, urinary system
43
Endoderm becomes....
Internal structures
44
Give some examples of internal structures that the endoderm becomes
lining of GI tract, lungs, glands associated with digestion, epithelia
45
What three cavities are present at week 3?
amniotic cavity yolk sac chronic cavity
46
On which side of the epiblast does the primitive streak appear?
dorsal
47
Where is the primitive node located?
At the cranial end of the streak
48
Where is the primitive pit located
At the centre of the primitive node
49
Which was does gastrulation proceed?
cranial to caudal i.e. cephalocaudally
50
When does migration and invagiantion complete?
week 4
51
Describe gastrulation
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
What is the notochord?
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
What is the significance of the notochord?
- defined the phylum chordata - defined midline - sets basis for axial skeleton which forms around it - drives neurlation (formation of the nervous system)
54
What is the notochord in adults?
It regresses and forms the nucleus pulposus of intervertebral discs.
55
What is the clinical significance of the notochord in later life?
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
Monozygote twins?
Are twins where 1 zygote has formed 1 infant
57
What is the name given to twins from 2 zygotes?
dizygote twins
58
If the embryo splits after the 2nd clevage?
the twins get their own placenta
59
If the inner cell mass/embryoblast duplicates?
the twins have their own placenta but the same amniotic sac
60
If the primitive streak duplicates?
The twins have their own placenta and amniotic sac
61
What is the name given to the genes that can be disrupted by certain substances during pregnancy?
Teratogenes
62
Why does the primitive streak define anterior and posterior?
because it appears at the end of the bilaminer disc
63
What does the primitive node ensure?
ensures correct dorsal-ventral and left-right development.
64
What is the condition when the visceria are mirror images?
situs inversus

Mine ESA 1 (7 decks)

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