Embryology 1.3 Flashcards

1
Q

What is implantation? (week 2 )

A

blastocyst burrows itself into the endometrial layer and stays there for 39 weeks after

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2
Q

Why is the blastocyst able to burrow into endometrial layer?

A

because of outer cell mass- trophoblast

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3
Q

What’s going to happen to the trophoblast ( the outer cell mass) ?

A

outer cell mass (initially a single layer) is going to divide and form two layers.
Cellular changes within cells until it becomes a chorion.

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4
Q

What is the chorion going to develop?

A

finger like processes called chorionic villi.

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5
Q

What are the functions of chorionic villi?

A
  1. Implantation process
  2. Forms part of the placenta in due course
  3. Secretes human Chorionic gonadotropin (HCG) (used to detect pregnancy)
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6
Q

Describe why the endometrium sheds?

A

Oestrogen and progesterone has a function of acting on this endometrium of the uterus and making it develop.
The endometrium keeps developing as long as the ovary keeps secreting this hormone. Hormones secreted for about 3 weeks and then ceased to be secreted.

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7
Q

What hormone does the chorion secrete to keep implanted embryo in endometrium?

A

Human Chorionic Gonadotropin

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8
Q

What does HCG encourage?

A

ovaries to keep producing oestrogen and progesterone

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9
Q

What has happened to the chorion at around weeks 12-15?

A

chorion developed into the placenta (has own system of blood vessels) and is now able to nourish the growing embryo

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10
Q

What are the side effects of HCG?

A

morning sickness

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11
Q

When does morning sickness disappear?

A

end of the first trimester

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12
Q

How do we detect pregnancy?

A

HCG in the urine

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13
Q

What is the decidua?

A

the endometrium after implantation has occurred

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14
Q

Recap of terminology?

A

zygote- first cell in the body that’s formed

morula- when zygote is divided and it forms that solid mass of cells

blastocyst- structure with cavity, outer and inner cell layer

trophoblast

chorion

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15
Q

What happens to the inner cell mass during second week?

A

inner cell mass going to flatten itself and form two layers.
The two layered flat disc is called the bilaminar disc

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16
Q

What are the two layers of the bilaminar disc called?

A

epiblast - top
hypoblast - hypoblast

17
Q

What is the cavity above the epiblast called?

A

amniotic cavity

18
Q

What is the cavity below hypoblast called?

19
Q

What will form the embryo?

A

the bilaminar disc

20
Q

What is completely covering the embryo?

A

amniotic sac

21
Q

What happens to the yolk sac?

A

becomes smaller

22
Q

What cavity also forms ?

A

allantoic cavity

23
Q

What cavity are all these structures developing in?

A

the chorionic cavity

24
Q

What will chorionic villi develop into?

A

the placenta

25
What are the main functions of the placenta?
foetal nutrition transport of waste and gases immune etc.
26
Describe foetal part and surface of placenta?
smooth with foetal blood vessels and end of umbilical cord
27
Describe maternal pat of the placenta?
decidua basalis of endometrium rough and has maternal blood vessels
28
What carries blood into the placenta?
two umbilical arteries and one umbilical vein that carry blood up into the placenta
29
When does placenta start to form and when does it mature?
starts to form about week 12 but it matures by about 18 to 20 weeks
30
How much does placenta weigh?
At birth, 1/6 of foetus
31
How are non identical twins formed (fraternal/dizygotic)?
2 ova being released and two sperms two zygotes different genetic makeup 2 placentae
32
How are identical twins formed ?
zygote divides into two and each cell develops into a diff embryo
33