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Body Logistics > L3) Embryology 1 ✔ > Flashcards

L3) Embryology 1 ✔ Flashcards

1
Q

define the pre-embryonic period of human development

A

first two weeks of development
processes involved include: cleavage, compaction and implantation begins

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2
Q

how does fertilisation occur?

A

oocyte released from ovary
travels along fallopian tube
fertilised by sperm in ampulla

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3
Q

what is a fertilised oocyte called?

A

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

briefly describe what occurs in week 1 - cleavage

A

30 hrs after fertilisation
cleavage results in two blastomeres of equal size
zona pellucida sustained

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6
Q

what is the zone pellucida?

A

protective glycoprotein shell

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7
Q

briefly describe what occurs in week 1 - post cleavage

A

after zygote undergoes 4 cleavage divisions
embryo now defined as morula (16 cells)

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8
Q

briefly describe what occurs in week 1 - compaction

A

morula cells shift to form the first cavity - blastocyst cavity
inner cell mass - embryoblast
outer cell mass - trophoblast
zona pellucida sustained
now defined as blastocyst

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9
Q

what is the function of the zona pellucida being sustained?

A

remains constant in size
hence any successive division of zygote results in smaller cell size

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10
Q

briefly describe what occurs in week 1 - hatching?

A

blastocyst hatches from zona pellucida
no longer constrained - can enlarge
now defined as a conceptus
can now interact with uterine wall

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11
Q

briefly describe what occurs in week 1 - implantation begins?

A

conceptus now = 100 cells
8/100 = form embryo
92/100 = begin development of metal membranes

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12
Q

broadly describe what occurs in week 2?

A

differentiation of outer cell mass and inner cell mass

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13
Q

what does the outer cell mass give rise to in week 2?

A

syncytiotrophoblast
cytotrophoblast

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14
Q

what does the inner cell mass give rise to in week 2?

A

epiblast
hypoblast
aka the bilaminar disc

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15
Q

what is the potency of cells before compaction?

A

totipotent
capacity to become any cell type

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16
Q

what is the potency of cells after compaction?

A

pluripotent
capacity to become one of many cell types

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17
Q

briefly describe the development of a conceptus by the end of week 2

A

the conceptus has implanted
the embryo has two cavities (amniotic cavity and yolk sac)
and is suspended from the endometrium by a connecting stalk
within a supporting sac (chorionic cavity)

18
Q

broadly describe the process of implantation

A

invasive process
interstitial
establishes maternal blood flow within placenta
establishes the basic structural unit of matron-fetal exchange

19
Q

why is implantation interstitial?

A

uterine epithelium is breached
conceptus implants within the uterine stroma

20
Q

why is it important to establish a maternal blood flow within the placenta?

A

allow support of the embryo from maternal circulation

21
Q

what is the basic structural unit of matron-fetal exchange?

A

the chorionic villus

22
Q

what are some assisted reproductive techniques?

A

in vitro - oocytes fertilised in vitro (lab) and allowed to divide to 4 or 8 cell stage
morula then transferred to uterus
allows for PGD

23
Q

what is PGD?

A

Pre-implantation Genetic Diagnosis
removal of cell from morula
to test fro serious heritable conditions prior to transfer of embryo into mother

24
Q

what are some conditions linked to implantation defects?

A

placenta praevia
ectopic pregnancy

25
Q

what is placenta praaevia?

A

implantation in the lower uterine segment
can cause haemorrhage in pregnancy
placenta blocks the cervical canal
requires C-section

26
Q

what is ectopic pregnancy?

A

implantation at site other than uterine body (mostly Fallopian tube)
can be peritoneal or ovarian
can quickly become life-threatening emergency

27
Q

briefly describe what occurs in week 2 - day 9?

A

at the embryonic pole - the rapid development of syncytiotrophoblast
at the abembryonic pole - primitive yolk sac formed - this is in contact with the cytotrophoblast layer

28
Q

briefly describe what occurs in week 2 - day 11?

A

primitive yolk sac membrane pushed away from cytotrophoblast layer by acellular extraembryonic reticulum
reticulum later converted to extraembryonic mesoderm by cell migration

29
Q

briefly describe what occurs in week 2 - day 12?

A

maternal sinusoids invaded by syncytiotrophoblast
lacunae becomes continuous with sinusoids
uteroplacental circulation begins
uterine stroma prepares for support of the embryo

30
Q

what are maternal sinusoids?

A

uterine capillaries that develop after implantation allow the exchange of gas and nutrients with the mother

31
Q

briefly describe what occurs in week 2 - day 13?

A

formation of secondary (definitive) yolk sac
pinches off the primitive yolk sac

32
Q

briefly describe what occurs week 2 - day 14?

A

spaces within extraembryonic mesoderm merge to form chorionic cavity
the embryo and its cavities are suspended by a connecting stalk
bleeding around now may be confused with menstrual bleeding

33
Q

what is the connecting stalk?

A

a column of mesoderm
future umbilical cord

34
Q

what is the balstocoele?

A

first cavity
formed as result of compaction

35
Q

what is the amniotic sac?

A

formed from spaces within epiblast

36
Q

what is the primitive yolk sac?

A

the exocoelomic cavity
formed from hypoblast lining blastocoele

37
Q

what is the secondary yolk sac

A

the difinitive yolk sac
formed within primitive YS

38
Q

what is the extraembryonic coelom?

A

the chorionic cavity/sac
formed from spaces within extraembryonic reticulum and mesoderm

39
Q

epidemiology of early pregnancy loss

A

app. 50% of all zygotes lost in the first 2-3 weeks
15% diagnosed pregnancies will miscarry
1% women suffer from recurrent miscarriages

40
Q

why is a Caesarean section indicated in placenta praevia?

A

as the placenta blocks the cervical canal
vaginal delivery can cause severe bleeding

41
Q

why is ectopic pregnancy a life-threatening emergency?

A

can cause your fallopian tube to burst open. without treatment, the ruptured tube can lead to life-threatening bleeding

Body Logistics (15 decks)

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