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SUGER > Fertilisation And Pregnancy > Flashcards

Fertilisation And Pregnancy Flashcards

1
Q

How long can sperm last

A

4-6 days

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2
Q

How long can egg survive

A

1-2 days

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3
Q

When can sperm be introduced for successful fertilisation

A

5 days before to 1 day after ovulation

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4
Q

Egg transport

A

Extruded from ovary as digestive enzymes break the surface membrane
Carried out in antral fluid
Smooth muscle and Fimbriae move egg to fallopian tube
Cilia present in fallopian tube which carry egg to uterus

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5
Q

What wafts egg down fallopian tube

A

Cilia

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6
Q

What helps to transport sperm

A

Fluid pressure of ejaculation

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7
Q

Sperm transport

A

Sperm move themselves using tail
Vagina is acidic and high in nutrients which sperm utilises
Glucose comes from presence of oestrogen

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8
Q

Glucose in uterus

A

Comes from presence of oestrogen
Higher oestrogen level —>more glucose—> longer sperm can survive

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9
Q

What is the viscosity of uterine mucus dependant on

A

Woman’s hormone levels

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10
Q

Capacitation

A

Maturation process of spermatozoon
Tails become stronger
Plasma membrane develops allowing fusion with egg to occur

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11
Q

Where does fusion of sperm and egg normally occur

A

Ampulla of fallopian tube

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12
Q

When does fusion of egg and sperm occur

A

Within hours of ovulafion

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13
Q

Glycoproteins on Zona pellucida

A

ZP3 receptors

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14
Q

Binding

A

Acrosome reaction- enzymes exposed to the Zona pellucida causing it to be digested

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15
Q

Formation of zygote

A

Head of sperm passes into the cytosol and fertilisation occurs

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16
Q

How is polyspermy prevented

A

Fertilisation causes a reaction which changes the membrane potential of the cell- preventing entry of other sperm
Done by exocytosis of vesicles containing enzymes to inactivate ZP3, hardening the Zona pellucida

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17
Q

How long after gamete fusion is meiosis II completed

A

4-7 hours

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18
Q

what happens to the 2nd polar body

A

Degenrated

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19
Q

Pronuclei

A

2 sets of haploid chromosomes are present
23 sperm and 23 egg
Equal in size and contain nucleoli

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20
Q

What happens after fusion of sperm and egg

A

Nucleoli migrate to centre of cell and haploid chromosomes fuse
DNA replication occurs in preparation for Meiotic divisions
Mitosis then occurs

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21
Q

What happens on days 2/3

A

Cleavage

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22
Q

Where does cleavage of zygote take place

A

Fallopian tube

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23
Q

What maintains contraction within tubes

A

Oestrogen

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24
Q

What allows zygote to pass through fallopian tube

A

Increase in progesterone causes smooth muscle relaxation

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25
Q

What happens during cleavage stage

A

No cell growth but cleavage occurs increasing the number of cells present
Each cell is totipotent so can develop into an entire individual

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26
Q

What happens day 4

A

Compaction

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27
Q

Compaction

A

Cells flatten and maximise space
Tight junctions form between cells
Polarisation of outer cells
Conditions allow for rapid differentiation

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28
Q

What happens day 5

A

Cavitation and differentiation

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29
Q

Cavitation and differentiation

A

Fluid filled cavity expands and forms blastocysts
>80 cells
Lost totipotency

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30
Q

Blastocyst

A

> 80 cells
Lost totipotency
Trophoblast = outer cell layer
Inner cell mass
Fluid filled cavity in middle

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31
Q

Trophoblast

A

Outer cell layer of blastocyst

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32
Q

What happens day 5-6

A

Expansion

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33
Q

Expansion

A

Cavity expands
Zona pellucida thins

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34
Q

What happens day 6+

A

Hatching

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35
Q

Hatching

A

Blastocyst expansion and enzymes
Embryo out of Zona pellucida- essential for implantation

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36
Q

Stages after fertilisation day 1 —> day 8/9

A

Fertilisation
2 cell stage
4 cell stage
8 cell- uncompacted morula
8 cell- compacted morula
Early blastocyst
Late stage blastocyst (hatching)
Implantation

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37
Q

Morula

A

Solid ball of cells

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38
Q

Morula —> blastocyst

A

through the segregation of an inner cell mass from an external trophoblastic cell layer

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39
Q

When does implantation occur

A

7 days after fertilisation
On 21st day of menstrual cycke

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40
Q

Upon implantation

A

Endometrial cells provide metabolic fuel for early growth
Occurs for first 5 weeks until fetal heart is fully functioning

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41
Q

When does Apposition occur

A

9 days post-fertilisation

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42
Q

Apposition

A

Hatched blastocyst orientates via embryonic pole
Synchronises with endometrium

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43
Q

Attachment stage

A

Integrins between endometrial endothelium and trophoblast cells

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44
Q

What 2 layers does the trophoblast split into

A

Cytotrophoblast
Syncytiotrophoblast

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45
Q

Invasion stage

A

Synctiotrophoblast erodes blood vessels by using enzymes to digest the basal lamina

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46
Q

Decidual reaction

A

Differentiation of stromal cells adjacent to blastocyst

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47
Q

Maternal recognition

A

Secretion of IL-2 prevents rejection
Completed by day 11 post fertilisation

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48
Q

Placenta

A

Interlocking fetal and maternal tissues
Organ of exchange between mother and fetus

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49
Q

Function of placenta

A

Nutrition
Gas exchange
Waste removal
Endocrine and immune support

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50
Q

What is the first stage of placental development

A

Implantation- outer layer of trophoblastic cell mass invades endometrium

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51
Q

Chorion structure

A

Outermost layer of trophoblast cells
High/vast capillary network

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52
Q

Chorion function

A

Supply embryonic portion of placenta
Extends chorionic villi into endometrium
Releases digestive enzymes which break endometrial vessels so become surrounded by pool of maternal blood

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53
Q

How does placental blood enter the chorion

A

Uterine vein

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54
Q

How does placental blood leave the chorion

A

Decidual (maternal chorion)

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55
Q

Barriers to transport

A

Fetal endothelial cells
Fetal connective tissue
Chorionic epithelial cells
Endometrial epithelial cells
Maternal connective tissue
Maternal epithelial cells

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56
Q

Where does the amniotic cavity form

A

Between inner cell mass and chorion

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57
Q

What does the fluid inside the amniotic cavity resemble

A

ECF

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58
Q

Function of amniotic fluid

A

Buffers mechanical disturbances and temperature changes

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59
Q

Amniotic sac

A

Epithelial cells lining amniotic cavity
Fuses with chorion so there is only a single combined membrane around the fetus

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60
Q

Which cells produce hCG

A

Trophoblast

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61
Q

When do trophoblasts produce hCG

A

When they begin endometrial invasion

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62
Q

Effects of hCG

A

Maintenance of corpus luteum
Stimulation of oestrogen and progesterone production - preventing menstruation

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63
Q

What does hCG stand for

A

Human chorionic gonadotropin

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64
Q

When does hCG secretion peak

A

60-80 days after last menstruation

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65
Q

Clinical use of hCG

A

Hormone detected in pregnancy tests

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66
Q

Levels of hCG during pregnancy

A

Peaks at 60-80 days after last menstruation
Rapidly decreases which is maintained until end of pregnancy

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67
Q

As hCG decreases

A

The placenta increases secretion of oestrogen and progesterone

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68
Q

Where is prolactin released from

A

Anterior pituitary

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69
Q

Function of prolactin

A

Involved in milk production
Prevention of ovulation

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70
Q

What control release of prolactin

A

Suckling

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71
Q

Levels of prolactin

A

Increases at end of pregnancy when oestrogen and progesterone decrease

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72
Q

Where is relaxin produced

A

Ovaries and placenta

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73
Q

Function of relaxin

A

Limits uterine activity
Softens cervix
Ripens cervix

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74
Q

Levels of relaxin

A

Increases early in pregnancy

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75
Q

Where produces oxytocin

A

Posterior pituitary

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76
Q

Function of oxytocin

A

Stimulates uterine contractions
Triggers caring behaviour

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77
Q

Levels of oxytocin

A

Secreted throughout pregnancy
Levels increase towards end of pregnancy

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78
Q

Function of prostaglandin

A

Initiates labour

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79
Q

Where are prostaglandins produced

A

Uterine tissue

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80
Q

2 types of prostaglandin

A

PGF2a
PGE2

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81
Q

Which is the most abundant prostaglandin

A

PGF2a

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82
Q

Which prostaglandin is 10x stronger

A

PGE2

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83
Q

When does the corpus luteum regress

A

After 3 months

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84
Q

Which cells continue to produce oestrogen and progesterone after the corpus luteum regresses

A

Trophoblast cells

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85
Q

Where do the androgens for oestrogen come from

A

Maternal ovaries
Maternal adrenal medulla
Fetal adrenal medulla
Placenta

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86
Q

Aromatase

A

Found in placenta
Converts androgens into oestrogen

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87
Q

What inhibits GnRH release

A

Increased progesterone

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88
Q

Maternal adaptations: cardiovascular changes

A

Increased cardiac output
Decreased systemic BP
Decreased total peripheral resistance
Increased uterine blood flow
Increased blood volume
Increased plasma and blood cell mass
Tachycardia

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89
Q

Maternal adaptations: respiratory changes

A

Increased alveolar ventilation

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90
Q

Maternal adaptations: GI changes

A

Increased acid reflux
Delayed gastric emptying -gastroparesis

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91
Q

What causes maternal GI changes

A

Fetus pressing on stomach

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92
Q

Maternal adaptations: skin changes

A

Linea nigra
Striae gravidae
Darkened areola on breasts

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93
Q

Linea nigra

A

Dark line down central abdomen

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94
Q

Striae gravidae

A

Stretch marks on lower abdomen

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95
Q

Maternal adaptations: biochemical changes

A

Weight gain
Increased protein and lipid synthesis
Insulin resistance

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96
Q

Why don’t obese women gain as much weight as underweight women when pregnant

A

Already have fat stores

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97
Q

Length of pregnancy

A

40 weeks from day of last menstrual cycle
38 weeks from ovulation/conception

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98
Q

What stops contractions occurring during pregnancy

A

Smooth muscle cells of myometrium are disconnected from each other
Maintained by progesterone

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99
Q

What allows for coordinated contractions

A

Increase in oestrogen at end of pregnancy signals smooth muscle cells to produce connexins to form gap junctions

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100
Q

What is cervical ripening

A

Growth and remodelling of the cervix

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101
Q

What stimulates cervical ripening

A

Oestrogen

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102
Q

What maintains the uterus seal during pregnancy

A

Progesterone

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103
Q

What seals the uterus during pregnancy

A

Collagen fibres

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104
Q

What causes the cervix to become soft and flexible

A

Breakdown of collagen caused by oestrogen progesterone and relaxin

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105
Q

Parturition

A

Birth process

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106
Q

What initiates labour

A

Increased oxytocin from mother
Oxytocin, vasopressin and cytokines from fetus

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107
Q

Pre-labour

A

Increased prostaglandins—> enhanced oxytocin actions
Increased pressure in cervix as a result of prostaglandins
Contraction of actomyosin in myometrium

108
Q

What hormones have increased levels during labour

A

PGF2a and oxytocin

109
Q

Result of increased PGF2a and oxytocin during labour

A

Positive feedback from the pressure on cervix leading to more release thus more contractions

110
Q

Intervals of contraction

A

10-15 minutes

111
Q

Stages of labour

A

Latent
Active
Post-partum

112
Q

Latent labour

A

Little dilation (8hours)

113
Q

Active labour

A

Organised contractions (5 hours)
Dilation and full expansion

114
Q

Movement of contraction

A

Top to bottom

115
Q

Maternal embryonic communication regulates

A

Features of blastocyst morphogenesis
Coordination of implantation
Maternal immunotolerance

116
Q

Developmental plasticity

A

Selecting the right phenotype to fit the anticipated future environment

117
Q

Potential short-term responses developmental plasticity

A

Epigenetic modifications
Altered intracellular signalling
Metabolic stress
Gene expression changes
Apoptosis
Cell proliferation disturbances

118
Q

Clinical uses/modifications of fertilisation

A

Artificial insemination
Embryo transfer
In vitro fertilisation
Intra-cytoplasmic sperm injection
Somatic nuclear transfer (cloning)
Sperm cell therapy
IPS cells

119
Q

What is oocyte activation triggered by

A

Phospholipase C zeta (PLCz)- a sperm protein

120
Q

Function of phopholipase C zeta

A

Activates the egg to release calcium from internal stores - facilitating fertilisation

121
Q

Why is oocyte activation essential

A

Essential for transformation of the decondensed sperm nucleus in to pronucleus

122
Q

Pronuclei

A

Fusion of 2 sets of haploid chromosomes
Equal size
Contain nucleoli

123
Q

How long after gamete fusion do the Pronuclei form

A

4-7 hours

124
Q

Syngamy

A

Male and female pronucleus migrate to centre
Haploid chromosomes pair and replicate DNA in preparation for first mitotic division
Pronuclear membranes breakdown
Mitotic metaphase spindle forms
46 chromosomes organise at spindle equator

125
Q

How long after fertilisation does the ooplasm divide

A

24 hours

126
Q

When does activation of the embryonic genome and start of embryonic transcription occur

A

4-8 cell embryo

127
Q

Totipotent

A

The nuclei of individual blast omelets are each capable of forming an entire fetus

128
Q

Size of morula

A

16 cells

129
Q

Trophectoderm

A

Tight junctions between outer single epithelial layer

130
Q

Inner cell mas

A

Pluripotent

131
Q

Why does the fluid filled cavity expand

A

Sodium pumped in which pulls water in by osmosis

132
Q

Which part of the blastocyst is extraembryonic

A

Trophectoderm

133
Q

Which part of the blastocyst is embryonic

A

Inner cell mass

134
Q

Energy metabolism of early preimplantation embryo

A

low ATP turnover
ATP/ADP ratio is high
Energy metabolism is characterised by oxidative phosphorylation of pyruvate
Glucose uptake and utilisation is low

135
Q

Energy metabolism of blastocyst stage

A

Metabolic activity rises sharply
ATP/ADP ratio falls reflecting an increase demand for energy eg protein biosynthesis and ion pumping associated with blastocoel cavity
Glucose is predominant exogenous energy substrate

136
Q

Genetic control of early cleavage

A

Maternal RNA

137
Q

Genetic control of blastocyst

A

Embryonic

138
Q

Metabolic and biosynthetic activity of early cleavage

A

Low

139
Q

Metabolic and biosynthetic activity of blastocyst

A

High

140
Q

Exogenous nutrient requirements of early cleavage

A

Simple
Low glucose
Non essential amino acids

141
Q

Exogenous nutrient requirements of blastocyst

A

Complex
High glucose
Essential and non essential amino acids
Vitamins

142
Q

What supplies exogenous nutrients in vivo

A

Cumulus cells
Fallopian tube secretions eg calcium, sodium, chloride, glucose, protein
Uterine secretions eg iron, fat soluble vitamins, glucose

143
Q

Insulin-like growth factor

A

IGF-I
IGF-II
Increase cell numbers in blastocyst

144
Q

Leukaemia inhibitory factor

A

Enhances embryo-endo interaction

145
Q

Length of cellular differentiation

A

10 days

146
Q

Histogenesis

A

3 germ layers of embryo form - gastrulation after implantation

147
Q

3 germ layers

A

Ectoderm
Mesoderm
Endoderm

148
Q

Implantation window

A

4 days (6-10 days post ovulation)

149
Q

Changes to uterus for implantation

A

Endometrial cell changes to help absorption of uterine fluid- bring the blastocyst nearer to the endometrium and immobilise it
Change in thickness of endometrium and its blood supply development
Formation of decidua

150
Q

What mediates embryo implantation

A

Hormones - sex steroids
Cell adhesion molecules
Proteases
Cytokines
Growth factors
5 genes upregulated during implantation window

151
Q

3 phases of embryo implantation

A

Apposition
Attachment
Invasion

152
Q

Apposition

A

Unstable adhesion of blastocyst to uterine lining
Synchronisation of embryo and endometrium (decidua)
Hatched blastocyst orientates via embryonic pole (always attached at the area above the inner cell mass)
Receptive endometrium

153
Q

When is the implantation window

A

Day 19-22

154
Q

Attachment stage of implantation

A

Stable/stronger adhesion
Penetrate with protrusions of the trophoblast cells (microvilli)
Massive communication between the blastocyst and endometrium conveyed by receptor-ligand interactions
Apical surfaces of the endometrial epithelial cells express variety of adhesion molecules (integrin subunits)
Trophoblastic cells also express integrins
Attachment occurs through the mediation of bridging ligands that connect with integrins on their surfaces

155
Q

How does the blastocyst and endometrium communicate

A

Receptor-ligand interactions

156
Q

How does attachment occur

A

Bridging of ligands that connect with integrins on their surfaces

157
Q

Invasion

A

Trophoblast protrusions continue to proliferate and penetrate the endometrium
•cells differentiate to become syncytiotrophoblast
•The trophoblast surrounding the ICM = cytotrophoblasts.
•Highly invasive - trophoblast quickly expands and erodes into endometrial stroma.
•Invasion is enzymatically mediated
•Syncytiotrophoblast erodes endometrial blood vessels
•Eventually syncytiotrophoblast comes into contact with maternal blood and form chorionic villi – in initiation of the formation of the placenta
•Blood filled lacunae form (spaces filled with maternal blood). Exchange nutrients and waste products.

158
Q

Cytotrophoblasts

A

Trophoblast surrounding inner cell mass

159
Q

Initiation of formation of placenta

A

Syncytiotrophoblast erodes endometrial blood vessels
•Eventually syncytiotrophoblast comes into contact with maternal blood and form chorionic villi – in initiation of the formation of the placenta
•Blood filled lacunae form (spaces filled with maternal blood). Exchange nutrients and waste products.

160
Q

Function of Decidual reaction

A

Promotes placental formation

161
Q

Decidual reaction

A

stromal cells adjacent to the blastocyst differentiate into metabolically active, secretory cells or Decidual Cells (under influence of progesterone)
•Secretions include growth factors/proteins to support growth of implanting blastocyst in the initial stages before the placenta is fully developed.
•Endometrial glands enlarge and local uterine wall becomes highly vascularised.
•The decidual reaction is not required for implantation e.g. ectopic implantation can occur anywhere in the abdominal cavity.

162
Q

Decidual cells

A

Metabolically active, secretory cells
Secretions include growth factors/proteins to support growth of implanting blastocyst in the initial stages before the placenta is fully developed

163
Q

Role of progesterone

A

Modifies the distribution of oestrogen receptors
•Stimulates secretory activity
•Stimulates stromal oedema
•Increases volume of blood vessels
•Primes decidual cells
•Stabilises lysosomes
•Might be an immunosuppresent
•May stimulate growth factors and binding proteins
•May regulate the formation of reactive oxygen species (reducing oxidative stress)

164
Q

Maternal recognition

A

Embryo is antigenically different from the mother
•At the same time as the decidual reaction, leukocytes in the endometrial stroma secrete interleukin-2 which prevents maternal recognition of the embryo as a foreign body during the early stages of implantation
•uterine natural killer cells

165
Q

Role of hCG

A

Essential to sustain early pregnancy
•ensures the corpus luteum continues to produce progesterone throughout the first trimester of pregnancy (prevents menstruation).
•Interacts with the endometrium via specific receptors
•Immunosuppressive – has highly negative charge, may repel the immune cells of the mother & protect the foetus.

166
Q

Slow rate of increase in hCG indicates

A

Slow rate of increase might indicate
–Early abortion
–Ectopic pregnancy
–Delayed implantation
–Inadequate trophoblast

167
Q

Rate of increase in hCG in first 10-12 days of pregnancy

A

Doubles every 1.3 days

168
Q

In vitro culture systems

A

Use a sequential culture medium – different composition at different stages

169
Q

Day 1-3 in vitro culture systems

A

Water, salts &ions
Pyruvate, lactate, protein
and
No/low Glucose
Non essential amino acids

170
Q

Day 3+ in vitro culture systems

A

Water, salts &ions
Pyruvate, lactate, protein
and
Glucose
Essential and non essential amino acids
Vitamins

171
Q

One-step in vitro culture systems

A

Culture day 1-6 in same media one media
–Let the embryo choose principal
–useful in uninterrupted systems like time lapse
–Why? Reduce stress, less disturbance, Increase embryo viability

172
Q

Maternal factors affecting embryo growth in vitro

A

Follicle environment
Oocyte maturity (hCG trigger 36 hours before egg collection)

173
Q

Embryonic factors affecting embryo growth in vitro

A

Cleavage rate, size of blastomeres, degree of fragmentation
Gross chromosome imbalance
Variations in embryo metabolism
Failure or abnormal formation of the blastocoel cavity

174
Q

Laboratory conditions affecting embryo growth in vitro

A

Exposure to light
Exposure to high oxygen concentrations
Changes in pH or osmolarity
Culture medium
Volatile organic compounds

175
Q

Embryo transfer

A

Select morphologically best embryo(s) to transfer on day 5.

•If any remaining embryos - cryopreserve.

•Need to be of good quality and correct stage

176
Q

Causes of failed implantation

A

Problem with the embryo - high proportion of embryos fail to implant
–Aneuploidy (40% IVF fertilised eggs abnormal)

•Interaction between embryo and uterus - insufficient trophoblast invasion
– miscarriage

•Insufficient invasion of maternal blood vessels
-Pre-eclampsia, poor foetal growth, hypertension

•Sperm problem – DNA fragmentation (abnormal genetic material). Increase miscarriage. Nutrition & lifestyle.

177
Q

Recurrent implantation failure

A

Failure to achieve a clinical pregnancy after transfer of at least 4 good quality embryos in at least 3 cycles

•Under the age of 40

178
Q

Causes of recurrent implantation failure

A

Poor ovarian function
•Increased sperm DNA fragmentation
•Uterine pathologies
–Polyps/fibroids
–Congenital anomalies
–Intrauterine adhesions
•Hydrosalpinges shown to significantly reduce implantation and preg rates - fluid toxic to embryos and affects endometrial receptivity.
•Immunological factor (NK cells)

179
Q

Management of recurrent implantation failure

A

Lifestyle changes (smoking, BMI)
•Sperm DNA fragmentation test
•Improve embryo selection e.g. PGT-A
•Hysteroscopy – remove anomalies
•Fibroid / Polyps /Hydrosalpinges removal
•Immunotherapy (intravenous immunoglobulin) – maybe only subgroup of women benefit.

180
Q

After fertilization, male and female pronucleuses are unified. What this process is called?

A

Syngamy

181
Q

What happens in the embryo after embryonic genome activation and before blastocyst formation?

A

Compaction

182
Q

Implantation happens after blastocyst has hatched through

A

Zona pellucida

183
Q

What is the best choice of treatment for:“A 36 year old man with 47XXY karyotype that is consistently azoospermic at semen analysis but has a small number of sperm recovered by testicular biopsy. His 31 year old partner is of normal biology with patent Fallopian tubes and has responded well to superovulation”

A

Intra-cytoplasmic sperm injection

184
Q

What promotes myometrial contraction

A

Prostaglandins in seminal fluid

185
Q

3 outcomes of cortical reaction

A

1 Slow polyspermy block
2 Completion of meiosis II
3 Zygote formation.

186
Q

Completion of meiosis II

A

The Ca2+ released during the cortical reaction acts at the nucleus of the secondary oocyte to stimulate the completion of meiosis II. As a result, there is a definitive ovum and a polar body; the latter is later degraded.

187
Q

Zygote formation and implantation

A

Finally, the pronucleus of the definitive ovum (n) is now able to fuse with the pronucleus of the sperm cell (n). This produces the zygote (2n).
The zygote continues to divide via mitosis within the fallopian tubes. At the 16-cell stage (3-4 days after fertilisation), the embryo is called a morula. All 16 cells of the morula are totipotent, and not specified to a particular fate. At day 5, the embryo becomes a blastocyst, characterised by the development of a distinct inner cell mass and blastocoele (fluid filled cavity), and surrounded by trophoblast cells. Implantation occurs on day 7-8, at the late blastocyst stage

188
Q

Polyspermy block

A

To prevent multiple sperm from binding to the cell membrane, there are two mechanisms of polyspermy block.
Fast Block: Na+ dependent, rapid onset, short duration
Binding of sperm to the cell membrane activates Na+ ion channels which allow for Na+ influx into the egg. This causes depolarisation, making the oocyte more positive and thus repelling further sperm and inhibiting them from binding. A fast block has a rapid onset, but short duration.
Slow Block: Ca2+ dependent (occurs secondary to the cortical reaction), slow onset, long duration
Fusion of the sperm and oocyte cell membrane activates the smooth endoplasmic reticulum (smooth ER), causing it to release large amounts of Ca2+. This stimulates intracellular lysosomes to release hydrolytic enzymes to further degrade the ZP, and stimulates exocytosis of cortical granules to harden the oocyte cell membrane, making it impenetrable to further sperm.
The slow block has a slower onset but is longer in duration.

189
Q

Polyspermmy fast block

A

Na+ dependent, rapid onset, short duration
Binding of sperm to the cell membrane activates Na+ ion channels which allow for Na+ influx into the egg. This causes depolarisation, making the oocyte more positive and thus repelling further sperm and inhibiting them from binding. A fast block has a rapid onset, but short duration.

190
Q

Polyspermy slow block

A

Ca2+ dependent (occurs secondary to the cortical reaction), slow onset, long duration
Fusion of the sperm and oocyte cell membrane activates the smooth endoplasmic reticulum (smooth ER), causing it to release large amounts of Ca2+. This stimulates intracellular lysosomes to release hydrolytic enzymes to further degrade the ZP, and stimulates exocytosis of cortical granules to harden the oocyte cell membrane, making it impenetrable to further sperm.
The slow block has a slower onset but is longer in duration.

191
Q

Cortical reaction

A

After the ZP is digested, a single sperm fuses with the cell membrane of the oocyte. This causes the smooth endoplasmic reticulum of the oocyte to release Ca2+, raising intracellular Ca2+ levels

192
Q

Sperm capacitation

A

Firstly, it prepares the sperm’s head for the acrosomal reaction. Secondly, the motility of the sperm is hyperactivated by the changes to the strength and speed of flagellum’s movements.

193
Q

Binding of sperm and egg

A

Once the capacitated sperm reach the secondary oocyte in the fallopian tube, there are multiple sperm-oocyte interactions that must occur before the sperm can fertilise the egg. The capacitated sperm first encounters the cumulus-oocyte complex surrounding the secondary oocyte, and a much high concentration of follicular fluid. Hyaluronidase present on the surface of the capacitated sperm head dissolves the hyaluronic acid cementing the cells of the COC together, enabling the capacitated sperm to penetrate the COC. The sperm then reach a layer of glycoproteins surrounding the oocyte, known as the zona pellucida (ZP). Binding to ZP3 causes the sperm’s plasma membrane to fuse with its acrosomal membrane, leading to the release of hydrolytic and proteolytic enzymes from the sperm’s acrosome. These enzymes digest the zona pellucida, enabling the sperm to reach the cell membrane.
Multiple sperm are involved in the above three processes. However, only one of these sperm will fuse and fertilise the oocyte.

194
Q

Sperm travelling to egg

A

After ejaculation, the semen immediately coagulates to form a loose gel, which holds the sperm at the cervical os and protects against the acidic pH and immunological response of the vagina.`At the cervix, the sperm encounters cervical mucus. High levels of oestrogen around the time of ovulation reduce its viscosity and alter its microstructure to allow for easier passage of the sperm through the cervix and into the uterus. Additionally, components of the seminal fluid assist the sperm to penetrate the mucus barrier.
Once the sperm enters the uterus, pro-ovarian contractions of the uterine myometrium help to propel the sperm towards the fallopian tube. Prostaglandins present in the seminal fluid promote these myometrial contractions.
The first sperm enter the fallopian tubes only minutes after ejaculation, however may survive in the female reproductive tract for up to five days.

195
Q

Combined hormonal contraception

A

uses oestrogen and progesterone
• Act primarily to inhibit ovulation due to negative feedback effect of the oestrogen and progesterone on the hypothalamo-pituitary axis- prevents LH surge thus preventing ovulation
• Progesterone also inhibits proliferation of the endometrium , creating unfavourable conditions for implantation and increases the thickness of the cervical mucus, preventing passage of sperm

196
Q

Progesterone only contraception

A

thickens cervical mucus preventing the entry of sperm
• Thins endometrium which inhibits implantation

197
Q

Causes of female factor infertility

A

1 Disorders of ovulation – most common cause of infertility in women
2 Tubal causes
3 Uterine/peritoneal causes
4 Other causes

198
Q

Disorders of ovulation

A

WHO has classified ovulation disorders into 3 categories:
Group I: hypothalamic pituitary failure (10%)
Hypothalamic amenorrhoea – can be due to low body weight/excessive exercise
Hypogonadotrophic hypogonadism e.g. due to Kallmann syndrome
Group II: hypothalamic-pituitary-ovarian (85%)
Predominately PCOS
Group III: ovarian failure (4-5%)
Hypergonadotropic hypogonadism

199
Q

Tubal causes of infertility

A

Pelvic inflammatory disease (PID) – see our article on PID for more information
Endometriosis
Previous sterilisation

200
Q

Uterine and peritoneal causes of infertility

A

Endometriosis
Previous pelvic surgery (formation of adhesions, including intrauterine)
Uterine fibroids
Uterine anomalies
Cervical factors

201
Q

Other causes of female infertility

A

Unexplained
Genetic factors
Immune factors and systemic illnesses
Medications: chemotherapy and cytotoxic agents
Lifestyle factors: smoking, excessive alcohol, obesity

202
Q

Endocrine and biochemical maternal adaptation to pregnancy

A

Weight gain
Protein synthesis
Lipid synthesis
Insulin resistance

203
Q

Pregnancy hormones

A

Human chorionic gonadotrophin
Oestrogen
Progesterone
Prolactin
Relaxin
Oxytocin
Prostaglandins

204
Q

Human chorionic gonadotrophin hormone function

A

Stimulates oestrogen/progesterone production in ovary

205
Q

Human chorionic gonadotrophin hormone diminishes when

A

Placenta is mature enough to take over oestrogen.progesterone production

206
Q

Oestrogen function

A

Regulates levels of progesterone
Prepares uterus for baby and breasts for lactation

207
Q

Progesterone function

A

Prevents miscarriage
Builds up endometrium for support of placenta
Prevents uterine contractions

208
Q

Prolactin function

A

Increases cells that produce milk
Prevents ovulation
After birht- stimulates production of milk and also controlled by suckling

209
Q

Relaxin levels

A

High in early pregnancy

210
Q

Relaxin function

A

Limits uterine activity
Softens the cervix- cervical ripening in preparation for delivery

211
Q

Oxytocin function

A

Triggers caring reproductive behaviour
Responsible for uterine contractions during pregnancy and labour

212
Q

Prostaglandins function

A

Tissue hormones
Initiation of labour

213
Q

Which drugs are used to induce labour

A

Oxytocin
Synthetic Prostaglandins

214
Q

Maternal cardiovascular changes

A

Increasing cardiac output
Reduced systemic blood pressure
Reduced total peripheral resistance
Increased uterine blood flow
Increased red cell mass

215
Q

Common maternal problems affecting pregnancy

A

Poor weight gain/undernutrition
Extremes of maternal age
Medical conditions
Drug misuse: cigarettes, heroin
Haemorrhage

216
Q

Common fetal problems

A

Miscarriage
Abnormal development
Disordered fetal growth
Premature birth

217
Q

What allows uterine growth

A

Cell division and hypertrophy of individual myometrial cells

218
Q

Uterine cervix

A

Protects fetus during development
Mainly collagen and ground substance with glycosaminoglycans
Collagen has cross-links which increase tensile strength

219
Q

Cervical ripening

A

Growth and remodelling of the cervix prior to labour
Occurs under influence of placental hormones and relaxin through gestation
Process accelerates in last 3 months due to oestrogens and dehydroepiandrosterone
Promoted by release of PGE from cervical mucosa- relaxin and placental oestrogens
Effacement and dilation due to muscular action of cervix and uterus

220
Q

Which hormone promote cervical ripening

A

PGE from cervical mucosa
Relaxin
Placental oestrogens

221
Q

PGE

A

Prostaglandins E

222
Q

The process of cervical ripening accelerates when

A

Last 3 months of pregnancy

223
Q

Cervical ripening increases in last 3 months due to

A

Oestrogens
Dehydroepiandrosterone

224
Q

What is the main prostaglandin released during labour

A

PGF2(Alpha)

225
Q

Which prostaglandin is more potent

A

PGE2 X10 more than PGF2(alpha)

226
Q

Events of pre labour

A

Enhanced prostaglandin production
Initiation of labour: maternal signal (oxytocin), fetal signals (oxytocin, vasopressin and cytokines)
PGF2(alpha) enchanted action of oxytocin
With increased pressure on cervix , increased release of PG from decidua and chorioamnion

227
Q

Fetal signals that initiate labour

A

Oxytocin
Vasopressin
Cytokines

228
Q

Components of labour

A

Passenger - th baby
Passages - the pelvis
Powers- the uterus

229
Q

The powers- the uterus

A

Braxton-Hicks contraction
Co-ordinate
Into-ordinate

230
Q

Labour action

A

Myosin can only react with actin when phosphorylated by MLCK
MLCK functionally dependent on Ca2+ ions and calmodulin but inactivated by its own phosphorylation

231
Q

What is MLCK functionally dependent on

A

Ca2+ ions
Calmodulin

232
Q

What is MLCK inhibited by

A

Its own phosphorylation

233
Q

Problems with contractions

A

Too strong/weak
Disorganised
Cervix too rigid
Cervix weak
Postpartum bleeding

234
Q

Problems with the stages of labour

A

Prolonged latent phase
Failure to progress in labour
Delayed 2nd stage - instrumental delivery
Delayed 3rd stage - manual removal of the placenta

235
Q

When does the placenta begin to develop

A

At blastocyst implantation

236
Q

Fetal surface of placenta

A

Umbilical cord attachment
Covered with amnion attached to chorionic plate
Umbilical vessels branch into anastomosing chorionic vessels

237
Q

Maternal surface of placenta

A

Cotyledons
Cobblestone appearance
Covered with maternal decidua basalis

238
Q

Implantation- placental development

A

1st stage
Adhesion/attachment of embryo trophoblast and endometrial epithelial cells

239
Q

3 main functions of placenta

A

Metabolism
Transport
Endocrine

240
Q

Placental metabolism

A

Synthesised glycogen, cholesterol and fatty acids
Provided nutrient and energy

241
Q

Placental transport

A

Gases and nutrition
Water, glucose and vitamins
Hormones - mainly steroid
Electrolytes
Maternal antibodies _IgG
Waste products
Drugs and their metabolites
Infectious agents

242
Q

Maternal antibodies cross placenta

A

IgG
Not IgM

243
Q

Placental hormones

A

Human chorionic gonadotrophin (hCG)
Human chorionic somatommotropin (hCS)
Human chorionic thyrotropin (hCT)
Human chorionic corticotropin (hCACTH)
Progesterone and oestrogen
Relaxin

244
Q

Function of human chorionic somatommotropin

A

Stimulates mammary development

245
Q

Haemolytic disease of the newborn

A

Fetus Rh+
Maternal Rh-
Fetal causes anti Rh antibodies
Dangerous for 2nd child

246
Q

Placenta accreta

A

Abnormal adherence with absence of decidua basalis

247
Q

Placenta percreta

A

Villi penetrate myometrium

248
Q

Placenta praevia

A

Placenta overlies internal os of uterus
Abnormal bleeding

249
Q

When does labour usually occur

A

37-42 weeks

250
Q

Patruition

A

Pregnancy

251
Q

Dilation of cervix - latent

A

<4 cm

252
Q

Active dilation of cervix

A

4-10cm

253
Q

3rd stage of labour

A

Delivery of placenta

254
Q

Stage 1 of labour

A

Dilatation of cervix

255
Q

Stage 2 of labour

A

Birth of fetus

256
Q

The human embryo develops in a number of discrete stages.

The Morula stage of embryonic development happens before which of the following?

A

Blastocyst formation

257
Q

The ovarian follicle is a collection of cells which surround a single oocyte.

Which one of these forms the inner most layer of an ovarian follicle?

A

Zona pellucida

258
Q

24-year-old woman presents with a two month history of heavy periods.

What is the name given to the part of the uterus that lies above the entrance of the Fallopian tubes?

A

Fundus

259
Q

23 year old women presents to her GP for advice on getting pregnant as she is experiencing difficulty conceiving.

Which of these events induces ovulation?

A

Increasing plasma oestrogen triggers a surge of Luteinising Hormone

260
Q

Pregnancy tests rely on the detection of hCG (human chorionic gonadotrphin).

Which of the following best describes the role of chorionic gonadotropin (hCG)?

A

stimulates the corpus luteum to produce progesterone beyond the 14 days after ovulation when the corpus luteum would normally regress.

261
Q

Where is hCG produced

A

Placenta

262
Q

When are hCG levels highest

A

First trimester but production is throughout pregnancy

263
Q

24-year old presents to her GP as they are having difficulty conceiving.

Where in vivo in the female reproductive tract does fertilisation normally take place?

A

Fallopian tubes

264
Q

The corpus luteum is the remains of an ovarian follicle after ovulation.

Which hormone is produced by the corpus luteum?

A

Progesterone

265
Q

Portal system is where the blood from the capillaries of one organ is transported to the capillaries of another organ via a connecting vein(s)

Which of these hormones is secreted directly into a portal system?

A

Gonadotropin-releasing hormone

SUGER (17 decks)

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