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RED > L12: Placenta > Flashcards

L12: Placenta Flashcards

1
Q

What weeks are for normal term pregnancy

A

37-42 weeks

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2
Q

At week 9 what is the embryo considered to be

A

A foetus

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3
Q

What is pregnancy considered to be from in terms of the date

A

1st of the last period

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4
Q

For implantation to take place what type of endometrium do we need

A

Receptive endometrium

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5
Q

When can implantation occur

A

Within the implantation window

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6
Q

Approximately when is the implantation window

A

In mid secretory phase

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7
Q

What are the 2 phases in the uterus cycle

A

Proliferative phase

Secretory phase

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8
Q

What is the proliferative phase about

A

Growing the endometrium

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9
Q

Under what hormone is the proliferative phase under the control of

A

Oestrogen

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10
Q

In the secretory phase what is the dominant hormone

A

Progesterone

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11
Q

What occurs in the secretory phases

A

1) oestrogen and progesterone are secreted from the corpus luteum
2) oestrogen and progesterone in moderate levels cause a negative feedback to the HPG and LH/FSH levels are suppressed
3) the progesterone matures the endometrium lining so it is receptive
4) as the corpus luteum degrades the oestrogen and progesterone levels decrease and the endometrium undergoes apoptosis so you get a period if implantation doesn’t occur

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12
Q

What occurs to the endometrium when it becomes receptive

A

Glands increase in secretions

Epithelium surface microvilli swell up (pinopodes) so they absorb the uterine fluid to help catch the blastocytes

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13
Q

Where does fertilisation occur

A

Ampulla of the uterine tube

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14
Q

Where does cleavage begin

A

In the uterine tube

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15
Q

At day 5 what forms

A

Blastocytst

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16
Q

At day 6 what happens to the blastocytes

A

Hatches from the zona pellucida

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17
Q

Between day8-9 what happens to the blastocytes that hatches

A

Implants to endometrium

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18
Q

What are the 3 phases of implantation

A

1) apposition
2) attachment
3) invasion

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19
Q

What occurs in apposition

A

Blastocyst loosely associates with the uterine wall (therefore is at risk of being washed off here)

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20
Q

What occurs in during attachment

A

Blastocyst firmly adheres to the endometrium by adhesion molecules and integrin

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21
Q

What happens during invasion

A

Blastocyst attaches to the uterine wall and triggers enzyme production which degrades and invades the glycogen rich endometrial stroma for nutrients

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22
Q

What is the decidua

A

A modified mucosal lining of the uterus the forms in preparation to pregnancy

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23
Q

Which hormone initiates decidualisation of the endometrium

A

Progesterone

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24
Q

What are the changes that occur in decidualisation

A 
Oedema 
Blood vessels leaky
Changes to extracellular matrix 
Angiogenesis 
Infiltration of uterine natural killer cells for immune tolerance for embryo 
Fibroblast 
Store glycogen and lipids 
Secrete proteins
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25
Q

At what day does the decidua surround the implanted blastocyst

A

Day 10

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26
Q

What are the 2 sides of a placenta

A

Embryo side

Maternal side

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27
Q

What are the structures in the maternal side

A

Chorion
Endometrial veins
Spiral arteries

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28
Q

How many types of placenta are there

A

3

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29
Q

What is the types of placenta based on

A

Structural organisation and separation of fetal and maternal blood

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30
Q

What are the 3 main types of placenta

A

1) haemochorial
2) endotheliochorial
3) epitheliochorial

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31
Q

Which type of placenta is found in humans

A

Haemochorial

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32
Q

What is the haemochorial

A

When the chorion is indirect contact with the maternal blood

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33
Q

As the blastocyst implants into the endometrium what happen to it

A

Differentiates

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34
Q

When the blastocyst undergoes differentiation what are the 3 main structures that form

A

Amniotic cavity
Bilaminar disc
Trophoectoderm (outer cell)

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35
Q

What is the bilmaninar disc composed of

A

Epiblast

Hypoblast

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36
Q

What are the 3 cell types the trophoectoderm gives rise to

A

Cytotrophoblast
Syncitiotrophoblast
Extravillous cytotrophoblast

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37
Q

What are the synctiotrophoblast and extravillous cytotrophast from

A

Cytotrophoblast

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38
Q

What happens to the syncitiotrophoblast

A

Gradually degrades its way into the endometrium tissue

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39
Q

What does the embryo gets its nutrients from

A

Products of glandular sections

Blood supply via spiral arteries

40
Q

What structures then begin to form in the syncitiotrophoblast

A

Lucunae (spaces)

41
Q

What does lucaneae store

A

Digested products of the cell and glands

42
Q

As the syncitiotrophoblast grows into the endometrium what structure does it hit

A

The maternal spiral arteries

43
Q

What does maternal vessel anastomose with

A

Lucunae

44
Q

What does anastomoses of lucunae and maternal vessels from

A

Sinusoids

45
Q

What begins the primary villi formation

A

When the cytotrophoblast begin to poke way down the syncitiotrophoblast between the sinusoids

46
Q

What forms the primary vili

A

Cytotrophoblasts extend into the syncitiotrophoblast to form finger like projections into the decidua

47
Q

After the primary vili what other villi begins to form/develop

A

Secondary villi

48
Q

What occurs to from the secondary villi

A

Extra-embryonic mesoderm behind the cytotrophoblast begins to push the structures in between the cytotrophoblast and syncitiotrophoblast

49
Q

After the secondary villi formation what villi begins to develop/form

A

Tertiary vili

50
Q

What occurs to from the tertiary villi

A

1) The extra embryonic mesoderm begins to differentiate
2) formation of blood vessels from the endothelial cells
3) these blood vessel fuse with the developing vessels to link the fetal blood via invading vessels from the umbilical cord
4) sinosoidal spaces also expand so you get the formation of intervillous space

51
Q

After the tertiary villi what happens to it

A

Matures to from the mature villi

52
Q

What happens to form the mature villi

A

1) Stem villi form which is attached to the choronic plate
2) from the stem villi, branch vili project
3) from the branch villi, terminal villi from

53
Q

Which villus is the main exchange with the maternal and fetal blood

A

Terminal villus

54
Q

When the mature villi has developed what villus do we get

A

Choronic villus

55
Q

What is the placental membrane

A

The distance of diffusion between the maternal blood and the fetal blood

56
Q

What is the placental membrane like in 10 weeks of gestation

A

Large

57
Q

What is the placental membrane large at 10weeks

A

The fetal blood is central placed and therefore further away from the maternal blood

58
Q

When does the placental membrane decreases/shorter

A

At term

59
Q

What allows the placental membrane to become shorter at term

A

More branches from
Syncitiotrophoblast thins down
Cytotrophoblast thins

60
Q

Which arteries from the mother bring in maternal blood around the choronic villi

A

The maternal spiral arteries

61
Q

Where does the maternal blood come into

A

The intervilous space (formed from the sinusoidal spaces)

62
Q

What happens to the maternal spiral arteries to allow for low resistance and high blood flow

A

Remodelling to increase the diameter

63
Q

Where does extravillous trophoblast form from

A

Cytotrophoblast at the tip of the anchoring villi

64
Q

When are extravillous cytotrophoblast form

A

When the anchoring villi form

65
Q

What happens to the extravillous cytotrophoblast when they form

A
  • Migrate into the decidua and block the spiral arteries

- remove smooth muscle and replace endothelium to from the endovascular trophoblast layer

66
Q

Why does the extravillous trophoblast cells block the spiral arteries

A

To create a low oxygen environment for the early foetus because it doesn’t have the mechanism to deal with oxidative stress yet

67
Q

At the end of which week does the extravillous trophoblast break down the plug in the spiral arteries to allow blood flow into the intervillous space

A

14

68
Q

Describe how remodelling of the spiral arteries occurs via extravillous trophoblast cells

A

1) interstitial EVT communicates with smooth muscles cells so they undergo apoptosis
2) interstitial EVT remodels the matrix and lays down material to from the scaffold support
3) endovascular EVT comes down inside the blood vessel to allows endothelial cells to undergo apoptosis
4) endovascular and interstitial EVT then replaces the endothelial cells.

69
Q

Overall what does the remodelling allow

A

Blood vessels that are larger in diameter, low resistance and high blood flow

70
Q

What are the 2 phases of nutrition for the embryo/foetus

A

1) histiotrophic phase

2) haemotrophic phase

71
Q

What is the histiotrophic phase

A

Fetus gets nutrients form the glandular secretion of endometrium and breakdown of products of decidua

72
Q

What is the haemotrophic phase

A

EVT plugs off the spiral arteries and blood flows into the placenta

73
Q

How does deoxygenated blood flow from the fetus to the placenta for exchange

A

1) umbilical arteries
2) fetal capilaries
3) choronic villus
4) stem villus
5) intermediate villi
6) terminal villi

74
Q

Which molecules can pass by diffusion across the placenta

A 
Oxygen 
Carbon dioxide 
Sodium 
Urea
Fatty acids
Sugars
75
Q

Which molecules need active transport across the placenta

A

Amino acids
Iron
Calcium

76
Q

Which substances are not transport across the placenta

A

Conjugated steroids

Most bacteria

77
Q

What are the harmful substances that can cross the placenta

A

Drugs
Caffeine
Alcohol
Cocaine

78
Q

What allows the fetus to pick up the oxygen from the mother with a higher affinity

A

Fetal haemoglobin

79
Q

What effects occurs to allow the gas exchange

A

Double Barr effect

80
Q

What is the double Barr effect

A

Carbon Dioxide from fetus is dumped to maternal blood so oxygen dissociates from mother

81
Q

What channels allow the diffusion of glucose across the placenta

A

GLUT1

GLUT3

82
Q

How are protein tranported to the fetus

A

1) proteins are broken into amino acids

2) amino acids transported take it up

83
Q

What does amino acids transporters require

A

ATP

84
Q

What hormone is amino acids transporter on fetus regulated by

A

Progesterone

85
Q

Which maternal antibodies can be transported to the fetus

A

IgG

86
Q

What is early onset pre-eclampsia

A

Insufficient penetration of EVT and lack of remodelling of the spiral arteries so spiral arteries have small diameter and therefore low blood flow when the spiral arteries unplug

87
Q

What can premature loss of EVT in spiral arteries lead to

A

Early initiation of blood flow that leads to miscarriage

88
Q

What is the treatment of pre-eclampsia

A

Delivery of placenta and baby

89
Q

What is intra-uterine growth restriction

A

When the baby does not grow as much as expected

90
Q

Why does intra uterine growth restriction occur

A

Due to blood flow on both sides of the placenta reduced

91
Q

What can intra uterine growth restriction be associated with

A

Pre-eclampsia

92
Q

What is the normal location of implantation

A

High up on the posterior wall of uterus

93
Q

Where else can the embryo implant that can be problematic

A

Marginal
Complete
Low lying

94
Q

What does the marginal, complete and low lying implantation cause

A

Barrier to escape of uterus in parturition

Risk of placental abruption leading to haemorrhage and death of fetus

95
Q

What is placenta accreta

A

The placenta attaches to the myometrium (deep layer) due to excessive trophoblast invasion instead of attaching to the endometrium (superficial layer)

96
Q

What is the treatment for placenta accreta

A
  • C-section of placenta

- Hysterectomy (if severe)

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