Fertilisation and placental development Flashcards Preview

203: Gynaecological pathology, common gynaecological disorders and sexual health > Fertilisation and placental development > Flashcards

Flashcards in Fertilisation and placental development Deck (27)
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1
Q

Fertilisation occurs where?

A

Ampulla of the fallopian tube

2
Q

First cleavage of zygote

A

Occurs at day one

- In the fallopian tube

3
Q

2-cell stage

A

Occurs at day 2

- In fallopian tube

4
Q

4 cell stage

A

Occurs at day 2

5
Q

Blastocyst

A

Forms at day 4, after fertilisation

Formed from the blastula which arranges into:

  • Inner cell mass–> embryoblast
  • Lined by trophoblast
  • Contained blastocele cavity
6
Q

Morula

A

Ball of cells from fertilised ovum, forms blastocyst.
- >8 cells

Day 4-5
- Develops a cavity–> blastocyst

7
Q

Trophoblast

A

Thin outer layer of the blastocyst

- Develops into placenta

8
Q

Day 6-7 of the embryp

A

Inner cell mass differentiates

  • Epiblast
  • Hypoblast

Hypoblast forms extraembryonic membrane and primary yolk sac

Epiblast forms embryo

Amniotic cavity originates from within epiblast.

The epiblast and hypoblast cells in contact forms the bilaminar disc of the embryo.

9
Q

Day 16+ of embryo

A

Bilaminar disc differentiation–> Gastrulation

Primitive streak initiates germ layer formation

  • Epiblast into ectoderm
  • Invading epiblast replace hypoblast–> endoderm
  • Epiblast also forms mesoderm

Epiblast forms all three germ cells cells

10
Q

Syncytiotrophoblast

A

Layer of cells external to the blastocyst

  • Full differentiated cells
  • Outer layer of the trophoblast
  • Invades the decidua (endometrium)

Directly in contact with maternal blood.

Produces placental hormones

11
Q

Cytotrophoblast

A

Cells that line inner layer of trophoblast
- Undifferentiated stem cells

Erodes maternal spinal vessel epithelium
- Gives rise to syncytiotrophoblast

Reduces as pregnancy advances

12
Q

Formation of placenta

A

Syncytiotrophoblast invades the decidua

Cytotrophoblast erode maternal spiral vessels
The lacunae spaces fill with maternal blood
- Mesoderm form fetal blood vessels

13
Q

Hormones produced by the placenta

A

hCG

  • Maintans corpus luteum
  • Stimulates oestrogen and progesterone release

Human placental lactogen (HPL)

  • Helps growth
  • Stimulates lactation
14
Q

Placental barrier

A

Composed of a monolayer of:

  • Syncytiotrophoblast (in direct contact with maternal blood)
  • Cyrotrophoblast
  • Fetal capillary epithelium

The barrier things as pregnancy advances= greater SA.

15
Q

Components that are transferred across the placenta

A

Gases
- Simple diffusion

Water and electrocytes

Steroid hormones

Proteins- pinocytosis

Maternal antibodies IgG

  • beings at week 12
  • Peaks after week 34
16
Q

Decidua

A

Modified endometrium

Three layers

  • Capsularis
  • Parietalis
  • Basali–> between uterine wall and chorionic villae
17
Q

Types of umbilical insertions

A

Central
- Normal

Marginal

Succenturiate

Circumvallate

Velamentous

18
Q

Velamentous cord insertion

A

When the umbilical cord inserts and transverses fetal membrane before entering fetus.

19
Q

Vasa praevia

A

When fetal blood vessel runs across the internal os opening

Complications

  • Massive, painless bleeding
  • Fetal death
  • Maternal death
20
Q

Positions of the placenta

A

anterior or posterior wall?

At the top? fundal

Placental praevia

21
Q

Failure of trophoblastic invasion into maternal circulation at 12-18 weeks

A

Poor mixing of blood leads to

  • Lack of o2 and nutrients
  • IUGR
  • Pre-clamspia
22
Q

Placenta accreta

A

When the placenta attaches too deeply into the uterine wall.

Accreta- Invasion into myometrium, not constricted by basalis

Increta
- Invasion into myometrium

Percreta
- Invasion into perimetrium

Complications

  • Severe bleeding
  • Treated with hysterectomy.
23
Q

Placental abruption

A

Premature separation of the placenta from the uterus

Complications

  • Very painful
  • Fetal/ maternal death
  • Massive bleeding
24
Q

DCDA

A

Either from dizygotic twins or monozygotic twins that split from between days 1-3.

25
Q

MCDA

A

Of monozygoic twins

Cleavage occurs days 4-8
- Single cell mass in blastula

Shared chorion, separate amniotic sac

26
Q

MCMA

A

Of monozygotic twins
-Cleavage occurs days 8-13.

Blastocyst has already implanted
- Major complications

27
Q

Conjoined twins

A

Occurs when splitting happens between days 13-15.

- Embryonic disc has formed.