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Semester 3 repro > Implantation, Placentation and Hormonal Changes in Pregnancy > Flashcards

Implantation, Placentation and Hormonal Changes in Pregnancy Flashcards

1
Q

What is a blastocyst?

A

→ An embryo at the 5th or 6th day of development

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2
Q

What does the embryoblast give rise to?

A

→ The fetus

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3
Q

What are the three layers of the blastocyst?

A

→ Trophoblast
→ Blastocoel
→ Embryoblast

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4
Q

What does the trophoblast give rise to?

A

→ The placenta

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5
Q

What is the blastocoel?

A

→ The fluid filled cavity

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6
Q

What are the two things needed for implantation to occur?

A

→ The blastocyst has to be fully mature

→ A receptive endometrium is needed which expresses receptivity markers to communicate with the blastocyst

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7
Q

Describe hatching

A

→The blastocyst hatches out of the zona pellucida due to expansions and contractions
→ this herniates the blastocyst out of the zona
→ digestive enzymes break down the opposite pole of where the blastocyst is

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8
Q

Where do the enzymes dissolve the zona?

A

→ Abembryonic pole

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9
Q

What are the three stages of implantation?

A

1) Apposition
2) Attachment
3) Invasion

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10
Q

What is Apposition?

A

→ Close positioning of the blastocyst to the endometrium

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11
Q

What is Attachment?

A

→ Cells of the trophoblast attaching to endometrium

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12
Q

What is Invasion?

A

→ Trophoblast cells multiply and invade the endometrium

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13
Q

Describe how the embryo implants (days 7-11)

A

→ The blastocyst attaches itself to the surface of the endometrial wall (decidua basalis)
→ Trophoblast cells start to assemble to form a syncytiotrophoblast to facilitate invasion
→ Syncytiotrophoblast further invades the decidua basalis and by day 11 it is almost completely buried

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14
Q

Describe the decidual reaction

A

→ High levels of progesterone results in the enlargement and coating of the decidual cells in glycogen and lipid-rich fluid
→ the fluid is taken up by the syncytiotrophoblast and helps sustain the blastocyst early on before the placenta is formed

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15
Q

What is a syncytiotrophoblast?

A

→ A group of trophoblast cells which are multinucleated

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16
Q

How are primary villi formed?

A

→ Cells of the syncytiotrophoblast start to protrude out to form tree-like structures known as primary villi which are formed around the blastocyst

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17
Q

How are lacunae formed?

A

→ Decidual cells between the primary villi begin to clear out leaving behind empty spaces known as lacunae

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18
Q

How does the junctional zone form?

A

→ Maternal arteries and veins grow into the decidua basalis
→ Blood vessels merge with the lacunae
→ Arteries fill the lacunae with oxygenated blood
→ Veins return the deoxygenated blood to the maternal circulation
→ Blood filled lacunae merge to a single large pool of blood connected to multiple arteries and veins
→this is known as the junctional zone

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19
Q

When is the umbilical cord formed?

A

→ Around week 5

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20
Q

Describe how chorionic frondosum form?

A

→ Day 17 the fetal mesoderm cells start to form blood vessels within the villi
→ a basic network of arteries, veins and capillaries
→ capillaries connect with blood vessels in the umbilical cord
→ villi grow larger in size and develop into chorionic frondosum

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21
Q

What separates maternal and fetal blood cells?

A

→ The outer lining of the primary villi is in contact with the junctional zone
→ The lining of the endothelial cells of the decidual from the mothers side

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22
Q

When do the decidual septa form?

A

→ 4th and 5th month

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23
Q

What is the function of decidual septa?

A

→ They divide the placenta into 15-20 regions

→ This gives it a much larger surface area in contact with the maternal blood

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24
Q

What is the umbilical cord made up of?

A

→ Two arteries and one vein

25
Q

What does the placenta take up?

A

→ O2 and glucose
→ immunoglobulins
→ hormones
→ toxins

26
Q

What does the placenta drop off?

A

→ Co2

→ Waste products

27
Q

What are the 4 functions of the placenta?

A

→ Provision of maternal O2, CHO, Fats, amino acids, vitamins, minerals, antibodies
→ metabolism - synthesis of glycogen
→Barrier - bacteria, viruses, drugs
→ Removal of fetal waste products : CO2, urea, NH4, minerals
→ Endocrine secretion e.g : hCG, estrogens, progesterone, HPL, cortisol

28
Q

How is the placenta adapted to its function?

A

→ Huge maternal uterine supply - low pressure
→ huge surface area in contact with maternal blood
→ huge reserve in function

29
Q

What is the placental barrier formed by?

A

→ Cells of the villi

30
Q

How many pregnancies does pre-eclampsia affect?

A

→ 3-4%

31
Q

When does pre-eclampsia start and how long can it last?

A

→ >20 weeks of gestation

→ can show up upto 6 weeks after delivery

32
Q

What does pre-eclampsia result in?

A

→ Placental insufficiency - inadequate maternal blood flow to the placenta during pregnancy

33
Q

What does pre-eclampsia cause?

A

→ new onset maternal hypertension and proteinuria

34
Q

What are the 7 risk factors for pre-eclampsia?

A 
→ First pregnancy
→ Multiple gestation
→ Maternal age > 35
→ Hypertension
→ DIabetes
→ Obesity 
→ Family history of pre-eclampsia
35
Q

What is eclampsia?

A

→ Pre-eclampsia + seizures

36
Q

What is pre-eclampsia caused by?

A

→ narrowing of maternal spiral arteries supplying blood to the placenta

37
Q

Describe how pre-eclampsia works?

A

→ Placenta responds by secreting pro inflammatory proteins
→ these enter the maternal circulation and cause dysfunction of the maternal endothelial cells
→ this causes vasoconstriction and affects other body systems

38
Q

What are the first signs of pre-eclampsia?

A

→ Proteinuria (impaired filtration)

→ high blood pressure

39
Q

Why does proteinuria occur during pre-eclampsia?

A

→ Glomerular damage

40
Q

What are the 6 risk factors for placental abruption?

A 
→ Blunt force trauma 
→ Smoking and drug use
→ multiple gestation
→ Maternal age > 35
→ previous placental abruption
→ hypertension from previous pre-eclampsia
41
Q

What are the symptoms of placental abruption?

A

→ Vaginal bleeding

→ Pain in back and abdomen

42
Q

What are the causes of placental abruption?

A

→ Degeneration of maternal arteries supplying blood to the placenta
→ Degenerated vessels rupture causing haemorrhage and separation of the placenta

43
Q

What are 4 complications that occur as a result of placental abruption?

A

→ Hypovolemic shock
→ Sheehan syndrome
→ Renal failure
→ Disseminated intravascular coagulation

44
Q

What is Sheehan syndrome?

A

→ Not enough blood to the pituitary

→ perinatal pituitary necrosis

45
Q

What are fatal complications of placental abruption?

A

→ Intrauterine hypoxia and premature birth

46
Q

What is placenta previa?

A

→ Placenta implants in the lower uterus

→ fully or partially covering the internal cervical os

47
Q

What is placenta previa associated with?

A

→ Increased chances of preterm birth and fetal hypoxia

48
Q

What are 7 risk factors associated with placenta previa?

A 
→ Previous C section
→ previous uterine/endometrial surgery 
→ uterine fibroids 
→ previous placenta previa 
→ smoking and drug use 
→ multiple gestation
→ maternal age > 35
49
Q

What is the cause of placenta previa?

A

→ Endometrium in upper uterus not well vascularised

50
Q

What do trophoblasts secrete?

A

→ hCG

51
Q

What is the function of hCG?

A

→ It binds to LH receptors on the CL

→ results in synthesis and secretion of progesterone and estrogen

52
Q

What is the ratio of progesterone to estrogen?

A

→ Progesterone is much higher

53
Q

When is there a decline in hCG and why?

A

→ At week 7

→ Placenta takes over and produces progesterone

54
Q

When does hPL increase?

A

→ Around week 5

55
Q

What is the function of hPL?

A

→ Makes the mother a bit more resistant to insulin so there is more glucose in the bloodstream available for mother and fetus

56
Q

How does the placenta make progesterone?

A

→ Cholesterol is received from the placenta
→ converted into pregnenolone and progesterone
→ it makes its way to the mothers circulation

57
Q

How does the placenta make estrogen?

A

→ Adrenal androgens from the fetus DHEA and DHEAS

→ placenta converts these into estrogens

58
Q

What is the cause of gestational diabetes?

A

→ hPL not functioning properly

Semester 3 repro (12 decks)

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