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REPRODUCTIVE AND DEVELOPMENTAL BIO > week 4 - implantation and pregnancy > Flashcards

week 4 - implantation and pregnancy Flashcards

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1
Q

when cyte is used at the end of a germ cell what does it mean? e.g. oocyte

A

haploid

in meiosis

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2
Q

when gonia is used at the end of a germ cell what does it mean? e.g. spermatogonia

A

diploid

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3
Q

At the zygote / ovum what can you see in the cell? (4)

A

Male and female pronuclei that havent fused yet

zona pelucida

cumulus cells

second polar body

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4
Q

When do male and female pro nuclei fuse? and what is the cell termed after they have fused?

A

syngamy

proper diploid cell

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5
Q

what is the zona pelucida?

A

it is what the sperm makes its way through and hardens afterwards
fuzzy gelatinous layer

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6
Q

You can see how many polar bodies at any one time in an ovum?

A

only ever one polar body

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7
Q

when the pro nuclei fuse the cell conceptus goes 2 cells, 4 cells, 8 cells, but the zona pelucida is still there so what occurs?

A

it cant grow
it means when the cells divide they are all small because the whole thing is constrained by the ZP, unless the ZP starts to thin and stretch the cells are confined

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8
Q

What is the morula?

A

ball of 16 cells

the ZP starts to thin and so growth can occur

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9
Q

what sort of growth occurs to the morula?

A

embryonic growth - giving rise to an embryo

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10
Q

within the morula the individual cells are termed what?

A

blastomere

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11
Q

every blastomere inside the morula is _____

A

totipotent - it can become anything

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12
Q

define pluripotent

A

cell has the potential to become one of several things

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13
Q

what happens when a totipotent cell is removed?

A

any other totipotent cell can replace it so offspring dont appear to be affected

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14
Q

what is the function of the ZP?

A

hardens and prevents polyspermy
keeps cells together
plays a crucial role in preventing chimeric embryos

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15
Q

what would happen if you have several embryos (polytocus mammal) and didnt have a zona pelucida around each one?

A

they would stick and fuse
the blastomeres from one embryo would transfer to another
this is demonstrated in mice in the lab where they exchange blastomeres during embryogenesis

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16
Q

when does the blastomere become a blastocyst?

A

when a cavity opens up in the middle of the morula due to geometry calculations and the sphere is getting larger at a faster rate than the exponential series of cells dividing

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17
Q

the cavity that opens up in the blastocyst is called ____

A

blastocoel

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18
Q

The blastocyst is the first time you see ___ between the cells

A

differentiation

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19
Q

what are the cells around the outside of the blastocyst called?

A

trophoblast

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20
Q

as well as the trophoblast and blastocoel there is one other structure in the blastocyst, what is it and what is its purpose?

A

pluriblast or inner cell mass (ICM)

goes onto make the embryo

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21
Q

what does the trophoplast do in the blastocyst?

A

contributes to the placenta

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22
Q

the blastocyst is a morula with individual blastomeres that are all ____

A

totipotent

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23
Q

Blastocyst derivatives

Trophoblast can be divided into ___ and ____, which contribute to the chorion

The pluriblast can be divided into ___ and ____.

The ____ goes onto form the yolk sac and the ___ will give us the various layers of the endoderm (___,___,___)

So why shouldnt you refer to a blastocyst as an embryo?

A

cytotrophoblast and syncyiotrophoblast

hypoblast and epiblast

hypoblst
epiblast
endoderm, mesoderm, ectoderm

Because the fetus is only a small portion of the blastocyst not all of it.

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24
Q

why does the blastocyst have to hatch?

A

— make its way out of the zona pelucida in order to divide —–needs to come out of the ZP to expose its surface in order to be able to attach to the endometrium

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25
Q

when the embryo attaches to the endometrium at which stage is the process irreversible?

A

adhesion

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26
Q

what are the 2 phases of embryo attachment?

A

apposition

adhesion

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27
Q

what is apposition?

A

when the embryo just touches the endometrium.

this process is reversible

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28
Q

what is adhesion?

A

the embryo is bound to the endometrium and depending on the species it may be invasion

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29
Q

the molecular mechanisms involved in apposition and adherence of embryos differ between ______ and include redundancy

A

differ between species

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30
Q

what is redundancy in terms of apposition and adhesion?

A

several molecules fulfil the same functions

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31
Q

if you see redundancy occurring what does it tell you?

A

that process is so important that it cant afford to go wrong

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32
Q

There are proteins and glycoproteins that are covering the endometrium and they can do 2 things?

A

attract an embryo

repel an embryo

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33
Q

The first thing you need to do in an embryo attachment is to get rid of anything that would block or deter an embryo………

A

need to down regulate endometrial molecules which would block / deter adherence – MUC1

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34
Q

MUC1 is an o linked glycoprotein that is upregulated by ____ and down regulated by ____

A

progesterone - puts more MUC1 on the endometrium

blastocyst - when the blastocyst arrives it gets rid of MUC1

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35
Q

You also need to before embryo attachment get more molecules that will attract the embryo…….

A

upregulate molecules which facilitate adherence to the endometrium such as LIF1

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36
Q

Estrogen induced ___ with paracrine roles in:

  • —____ of endometrium
  • —up regulation of _______ ____
A

cytokine
decidualisation
EGF family (epidermal growth factor)

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37
Q

what is decidualisation?

A

changes in the endometrium to make it ready for the embryo

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38
Q

how does the ZP dissolve?

A

EGF family members include heparin binding EGF like growth factor, which activates EGF receptors plus heparan sulphate glycoproteins (HSPG) on the trophoblast to dissolve the ZP

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39
Q

due to redundancy there are many other proteins implicated in embryo apposition including (5)

A 
integrins
selectins
ECM molecules (extra cellular matrix)
trophinin bystatin tastin complex
frizzled notch interactions
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40
Q

between ungulates and rodents/lagomorphs/primates the major difference in timing of embryonic events in days post ovulation is in the ____

A

blastocyst attachment where it can take anywhere between 2-6 weeks for the embryo to attach. it is free floating in the uterine cavity.

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41
Q

the biggest challenge faced by the embryo in ungulates is?

A

nourishment as it is free floating for up to 6 weeks in the uterine cavity. where does it get its nourishment from

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42
Q

embryo implantation can be 2 types -

A

invasive

non - invasive

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43
Q

what is invasive embryo implantation?

A

breach endometrial epithelium to invade the underlying stroma - e.g. primates, carnivores, rodents

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44
Q

what is non invasive embryo implantation?

A

endometrium or epithelium intact or locally disrupted, embryo stays on the surface of the uterus - e.g. ungulates

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45
Q

in non invasive implantation the blastocyst grows rapidly, but which part and why?

A

the blastocyst has 2 cell populations there is the trophoblast the cells around the outside that grow quickly and this is all about providing the maximum surface area because its for maximum absorption of nutrients

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46
Q

in non invasive implantation the embryos dont go through the epithelium they sit on the surface how?

A

on the embryo cotyledon and on the endometrium caruncle

caruncle - cotyledon sit together but never breach each other

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47
Q

in invasive implantation the blastocyst implants while _____ and the trophoblast invades between epithelium and underlying ____

A

small

stroma

48
Q

when the trophoblast is invading the stroma undergoes decidualisation reaction and the quality of this response determines what?

A

how far the embryo invades
depth of invasion limited by speed of stromal / decidual response

poor decidiual response = deeper invasion

49
Q

on the trophoblast cells what attach it to the endometrium?

A

the villi

50
Q

if there is no ZP around the trophoblast then what would happen?

A

you would get an eptopic pregnancy as the villi of the trophoblast cells would attach to anywhere

51
Q

invasive implantation appears to be an ____ cascade

A

inflammatory

52
Q

for the inflammatroy cascade we need up regulation of _____ and simultaneously of ____

A

MMP’s - enzymes that will break down the extracelllular matrix
TIMP’s - tissue inhibitors of metaloproteanases

need timps simultaneously because need to confine the MMPs so they dont break down extracellular matrix of everythign

53
Q

what is good evidence that the inflammatory cascade is required for implantation?

A

if we were to cause inflammation of the endometrium by scratching the endometrium the women who have had miscarriages the chance of an embryo sticking increases massively so clearly there is a problem with their inflammatory response and you need to induce it prior to the embryo trying to implant

54
Q

what is the mothers contribution to the placenta?

A

she provides the decidulate

55
Q

what is decidualisation in detail? (4)

A

rapid changes in the endometrial stroma underlying the conceptus including:

  • –increased vascular permeability
  • –oedema
  • -loosening of the ECM between cells
  • -stromal cell differentiation
56
Q

Decidualisation looks to be an inflammatory cascade mediated by: (5)

A 
increased prostaglandins
pro-inflammatory cytokines
VEGFs
angiopoiteins
proliferin
57
Q

implantation and decidualisation is an inflammatory response and we need to make sure it doesnt go too far so you do what?

A 
produce something (cortisol?) which will stop the inflammation before it goes too far
upregulation of an enzyme which generates active cortisol from inert cortisone
58
Q

in rodents decidualisation is _____

A

induced by presene of embryo

59
Q

in rodents there are what sort of decidualisation reactions?

A

primary (local) followed by secondary (widespread)

60
Q

placental classification is based on the shape of placenta, what are the 4 types?

A

discoid
zonary
cotyledonary
diffuse

61
Q

explain discoid placenta

A

distinct disc on a particular region on the implanting blastomyst that will become the placenta

62
Q

examples of animals with a discoid placenta

A

primates, lagomorphs, rodents

63
Q

explain zonary placenta

A

placenta in a discrete zone on the blastomyst it is a ring

64
Q

examples of zonary placenta

A

carnivores and seals and elephants

65
Q

explain cotyledonary placenta

A

it is not a single structure (be that a disk or zone) but there are lots of little points of contact between the trophoblast (cotyledons) and specific points on the endometrium (coruncles)

66
Q

example of cotyledonary placenta

A

sheep cow giraffe deer and goat

67
Q

explain diffuse placenta

A

general contact between the embryo and endometrium - light contact which is easily broken in many places

68
Q

example of diffuse placenta

A

lorises lemurs pig horse

69
Q

Another way of defining the placenta is based on which type of maternal tissue the embryo is in contact with (4)

A

blood
capillary endotheium
endometrial endothelium
epithelial syncytium

70
Q

explain a blood placenta with examples

A

the maternal tissue that contacts the foetal tissue is blood

primates and rodents -HAEMOCHORIAL

71
Q

explain a capillary endothelium placenta with examples

A

carnivores
zonary placenta contacts the endothelium cells from mums capillaries between her blood flow and the foetal blood flow
ENDOTHELIOCHORIO

72
Q

explain an endometrial epithelium with examples

A

sheep and cow
non invasive implantation
foetal tissue are not in touch with blood vessels or blood but the endometrium epithelium
EPITHELIOCHORIAL

73
Q

explain an epithelial syncytium with examples

A

pigs and horses
rather than contacting the epithelium there are a special set of cells between mothers epithelium and binutriate cells which are special cells from the foetus and they fuse to form a syncytium
SYNEPITHELIOCHORIAL

74
Q

can also classify placenta based on the number of layers in the chorionic trophoblast (3)

A

one two or three

75
Q

explain the 5 full types of placenta

A

haemomonochorial
haemodichorial
haemotrichorial

diffuse epitheliochorial
cotyledonary synepitheliochorial

76
Q

what are the 5 challenges faced by an embryo?

A

preventing the demise of the corpus luteum (CL)

growth and development
nutrition
gaseous exchange
elimination of waste

77
Q

why must the embryo prevent the demise of the CL?

A

because when the CL stops producing progesterone the endometrium will be shed and youve just implanted in something that is going to be lost

78
Q

what is luteolysis?

A

maternal recognition of pregnancy (MRP)

—rescuing the CL so it continues to produce progesterone

79
Q

most mammals require the early embryo to produce or stimulate the production of (2)?

A

luteotrophin - soething that will keep the CL alive and stop it shrinking

anti luteolysin - something that prevents a luteolysin (something which will kill the CL)

80
Q

chorionic gonadotrophin (CG) is produced where?

A

in the pre implantation trophoblast

81
Q

in humans what is CG shortened to? and in monkeys?

A

hCG

mCG

82
Q

mCG and hCG are very similar in molecular structure to which hormone?

A

LH (luteinizing hormone)

83
Q

MRP in primates - CG

hCG and mCG activate the same G protein coupled receptor as LH. The __ ___ is dependent on CL and with out it what happens?

A

corpus luteum

dies

84
Q

so to maintain the pregnancy in the early stages and prevent the demise of the CL what do we do?

A

stimulate the same receptor LHGCR and this will upregulate the same genes as LH does and will increase the output of steroid from that CL

85
Q

what synthesises and secretes equine chorionic gonadotrophin? (eCG)

A

trophoblast in the endometrial cups - remember horse has a diffuse placenta

86
Q

eCG mimics which hormone?

A

FSH

87
Q

what does eCG do in addition to activating LHCGR?

A

it will also stimulate FSHR and stimulates more follicles to develop which make more CL.

This animal is already pregnant and yet the embryo is going to make more ovulations happen in order to form more CL to contribute progesterone for the embryo

88
Q

Why is luteolysis well studied in ruminants?

A

big financial implications for farming

89
Q

what is different with the death of the CL in ruminants?

A

doesnt happen just because the LH runs out

there is an active destructional component that comes from the uterus to kill the CL - PF2alpha

90
Q

so what is happening with the CL and uterus in ruminants?

A

CL makes oxytocin a protein that stimulates the production of the PGF2 alpha in the endometrium that will kill the CL.

In the case of pregnancy an embryonic calf or lamb will make interferon tau and this switches off the oxytocin receptor so the CL survives

91
Q

how long is the CL needed during pregnancy?

A

varies with species

92
Q

in humans without pregnancy the CL lasts how long?

A

2 weeks

93
Q

if your menstrual cycle changes is it ovulation or the CL that changes?

A

ovulation

the CL is always a fixed number of days

94
Q

if a women conceives the CL will survive for how long?

A

9 months rescued by hCG

95
Q

do we need the CL for the entire pregnancy?

A

no only 3 months after that progesterone comes from the placenta

96
Q

why shouldnt you tell people you are pregnant before 12 weeks?

A

because prior to this you are functioning off the CL and at 12 weeks you test the placenta for the first time where a large number of pregnancies fail

97
Q

what happens in the absence of conception in a dog?

no embryo is produced what happens to the CL?

A

the sensible thing would be that the CL dies quickly and the dog comes back into heat again

dogs show this pattern regardless of whether they conceive, they have their CL for 60 days
there is no MRP

98
Q

how does the CL impact the dogs LRS/LRO?

A

every time she ovulates and produces a CL there are 60 days when there are no more follicles developing even if she is not pregnant.
this reduces her fertility massively as it is wasted time

MRP increase your feritlity

99
Q

What is the life of the CL in rats?

A

if they have not mated 2 days

if they are pregnant 22 days

if that female is mated but there is no pregnanacy the CL lasts for 12 days - pseudopregnancy

the rat when mated assumes she is pregnant and waits until 12 days to check

100
Q

what are the challenges faced by the mother?

A

growth and development
nutrition
gaseous exchange
elimination of waste

all the same as the challenges faced by the embryo / foetus she just cant do anything about the CL

101
Q

At any one time cells either proliferate or differentiate.
What is the cellular priority for the pre-implantation embryo?
What is the cellular priority for post implantation embryo?

A

proliferation - grow as fast as you can

differentiation

102
Q

when is it an embryo until? when does it become a foetus?

A

its an embryo until all the tissues have differentiated but cant rush this differentiation as need to proliferate to be a certain size first

103
Q

what is the cellular priority for the foetus?

A

proliferation - hyperplasia

104
Q

prior to the establishment of the placenta embryonic nutrition is ____

A

histiotrophic

tissue nutrition

105
Q

where do the histiotrophic nutrients come from?

A

metabolising the decidual stromal cells - carbs lipids etc

glandular secretions

106
Q

after establishment of the highly vascularised placenta embryo and fetal nutrition become ___

A

haemotrophic - blood derived nutrition

107
Q

In the early stages of embryogenesis we get fusion of the yolk sac mesoderm and the chorion, this is when we form the first placenta called_____

A

choriovitelline — yolk sac placenta

108
Q

In most eutheria the choriovitelline is short lived and replaced by the _____

A

chorioallantoic

109
Q

In metatheria the choriovitelline is the sole source of ____

A

nutrition

110
Q

In lagomorphs what happens to the choriovitelline?

A

it doesnt get exhausted but plays a secondary role during the pregnancy

111
Q

what is the chorioallantoic placenta?

A

this is the chorion and the allantois

112
Q

what is the allantois?

A

a piece of the endoderm that comes away from the hind gut

113
Q

the chorioallantoic placenta is where we get the major role in the ___

A

haemotrophic nutrition

114
Q

the interface in the haemochorial placenta is formed by the ___

A

cytotrophoblast (CTB)

115
Q

the CTB can fuse to give us _____

A

syncytiotrophoblast which then fuses with the extraembryonic mesoderm to form the chorion

116
Q

the chorion is going to fold into villi into which will fold microvilli providing ______ to be bathed in blood if its a haemochorial placenta

A

maximum surface area

REPRODUCTIVE AND DEVELOPMENTAL BIO (13 decks)

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