Implantation, Placentation and Hormonal Changes in Pregnancy Flashcards Preview

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Flashcards in Implantation, Placentation and Hormonal Changes in Pregnancy Deck (58)
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1

What is a blastocyst?

β†’ An embryo at the 5th or 6th day of development

2

What does the embryoblast give rise to?

β†’ The fetus

3

What are the three layers of the blastocyst?

β†’ Trophoblast
β†’ Blastocoel
β†’ Embryoblast

4

What does the trophoblast give rise to?

β†’ The placenta

5

What is the blastocoel?

β†’ The fluid filled cavity

6

What are the two things needed for implantation to occur?

β†’ The blastocyst has to be fully mature
β†’ A receptive endometrium is needed which expresses receptivity markers to communicate with the blastocyst

7

Describe hatching

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

8

Where do the enzymes dissolve the zona?

β†’ Abembryonic pole

9

What are the three stages of implantation?

1) Apposition
2) Attachment
3) Invasion

10

What is Apposition?

β†’ Close positioning of the blastocyst to the endometrium

11

What is Attachment?

β†’ Cells of the trophoblast attaching to endometrium

12

What is Invasion?

β†’ Trophoblast cells multiply and invade the endometrium

13

Describe how the embryo implants (days 7-11)

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

14

Describe the decidual reaction

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

15

What is a syncytiotrophoblast?

β†’ A group of trophoblast cells which are multinucleated

16

How are primary villi formed?

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

17

How are lacunae formed?

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

18

How does the junctional zone form?

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

19

When is the umbilical cord formed?

β†’ Around week 5

20

Describe how chorionic frondosum form?

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

21

What separates maternal and fetal blood cells?

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

22

When do the decidual septa form?

β†’ 4th and 5th month

23

What is the function of decidual septa?

β†’ They divide the placenta into 15-20 regions
β†’ This gives it a much larger surface area in contact with the maternal blood

24

What is the umbilical cord made up of?

β†’ Two arteries and one vein

25

What does the placenta take up?

β†’ O2 and glucose
β†’ immunoglobulins
β†’ hormones
β†’ toxins

26

What does the placenta drop off?

β†’ Co2
β†’ Waste products

27

What are the 4 functions of the placenta?

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

28

How is the placenta adapted to its function?

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

29

What is the placental barrier formed by?

β†’ Cells of the villi

30

How many pregnancies does pre-eclampsia affect?

β†’ 3-4%

31

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

β†’ >20 weeks of gestation
β†’ can show up upto 6 weeks after delivery

32

What does pre-eclampsia result in?

β†’ Placental insufficiency - inadequate maternal blood flow to the placenta during pregnancy

33

What does pre-eclampsia cause?

β†’ new onset maternal hypertension and proteinuria

34

What are the 7 risk factors for pre-eclampsia?

β†’ First pregnancy
β†’ Multiple gestation
β†’ Maternal age > 35
β†’ Hypertension
β†’ DIabetes
β†’ Obesity
β†’ Family history of pre-eclampsia

35

What is eclampsia?

β†’ Pre-eclampsia + seizures

36

What is pre-eclampsia caused by?

β†’ narrowing of maternal spiral arteries supplying blood to the placenta

37

Describe how pre-eclampsia works?

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

38

What are the first signs of pre-eclampsia?

β†’ Proteinuria (impaired filtration)
β†’ high blood pressure

39

Why does proteinuria occur during pre-eclampsia?

β†’ Glomerular damage

40

What are the 6 risk factors for placental abruption?

β†’ Blunt force trauma
β†’ Smoking and drug use
β†’ multiple gestation
β†’ Maternal age > 35
β†’ previous placental abruption
β†’ hypertension from previous pre-eclampsia

41

What are the symptoms of placental abruption?

β†’ Vaginal bleeding
β†’ Pain in back and abdomen

42

What are the causes of placental abruption?

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

43

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

β†’ Hypovolemic shock
β†’ Sheehan syndrome
β†’ Renal failure
β†’ Disseminated intravascular coagulation

44

What is Sheehan syndrome?

β†’ Not enough blood to the pituitary
β†’ perinatal pituitary necrosis

45

What are fatal complications of placental abruption?

β†’ Intrauterine hypoxia and premature birth

46

What is placenta previa?

β†’ Placenta implants in the lower uterus
β†’ fully or partially covering the internal cervical os

47

What is placenta previa associated with?

β†’ Increased chances of preterm birth and fetal hypoxia

48

What are 7 risk factors associated with placenta previa?

β†’ Previous C section
β†’ previous uterine/endometrial surgery
β†’ uterine fibroids
β†’ previous placenta previa
β†’ smoking and drug use
β†’ multiple gestation
β†’ maternal age > 35

49

What is the cause of placenta previa?

β†’ Endometrium in upper uterus not well vascularised

50

What do trophoblasts secrete?

β†’ hCG

51

What is the function of hCG?

β†’ It binds to LH receptors on the CL
β†’ results in synthesis and secretion of progesterone and estrogen

52

What is the ratio of progesterone to estrogen?

β†’ Progesterone is much higher

53

When is there a decline in hCG and why?

β†’ At week 7
β†’ Placenta takes over and produces progesterone

54

When does hPL increase?

β†’ Around week 5

55

What is the function of hPL?

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

56

How does the placenta make progesterone?

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

57

How does the placenta make estrogen?

β†’ Adrenal androgens from the fetus DHEA and DHEAS
β†’ placenta converts these into estrogens

58

What is the cause of gestational diabetes?

β†’ hPL not functioning properly