9.0 Placentation Flashcards Preview

MedST IB: Human Reproduction (HR) > 9.0 Placentation > Flashcards

Flashcards in 9.0 Placentation Deck (28)
Loading flashcards...
1

What does the inner cell mass differentiate into?

1) Epiblast (contacts trophoblast)
2) Hypoblast (faces blastocele)
3) Mesoderm (develops in between the other 2 layers)

2

What layer forms the extra-embryonic mesoderm?

Hypoblast

3

What are the two layers of extra-embryonic mesoderm?

1) Chorion (applied to inside of trophoblast)
2) Cell layers that covers outer surface of yolk sac and amnion

Extra-embryonic coelom is found in between the above two layers

4

When is the extra-embryonic coelom obliterated?

12 weeks
Amnion expansion → obliteration of extra-embryonic coelom

5

Features of the outer surface of yolk sac:

1) Acts like absorptive epithelium
2) Contains transports (GLUT1)
2) Secretes proteins (alpha-fetoprotein)

6

Functions of placenta:

1) Gas exchange
2) Excretion, water and pH balance
3) Reabsorptive features
4) Synthesis and secretory function
5) Metabolic and secretory function
6) Immunological/protective

7

What shape is the placenta?

Discoid

8

What is the diameter of the placenta?

20-25cm

9

What is the weight of the placenta?

400-600g

10

What are the two layers of the placenta?

1) Choronic plate
- Facing fetus

2) Basal plate
- Facing decidua basalis

11

What are the two layers that the trophoblast differentiates into on contacting uterine epithelium?

1) Syncytiotrophoblast (SCT)
- Multinucleated
- Non-proliferative

2) Cytotrophoblast (CTB)
- Deeper

12

What do STB and CTB become? (brief overview of steps)

STB → invade decidua → spaces form lacunae where maternal secretions and blood enter

CTB + extraembryonic mesoderm infiltrate trabeculae (in between lacunae) → placental villi

13

Where do stem villi arise from?

Chorionic plate

14

Where do anchoring villi connect to?

Basal plate

15

When do terminal villi form?

2nd 1/2 of gestation

16

What is the main nutrient source in histiotrophic nutrition?

Carbohydrate and lipid secretions from the endometrial glands

Glands are stimulated by progesterone from the corpus luteum

17

When does haemotrophic nutrition start?

Week 12 of pregnancy

18

What are the features of the embryonic period of pregnancy?

- Histiotrophic nutrition
- Organogenesis
- Susceptible to malformation

19

What are the features of the fetal period of pregnancy?

- Haemotrophic nutrition
- Growth and functional maturation

20

What is the surface area of the placental villous tree?

12-14m²

21

What cells need to be present for conversion of spiral arteries?

Extravillous trophoblast cells

22

How to EVT cells migrate to spiral arteries?

From tips of anchoring villi. Via 2 methods:
1) Endovascular
2) Interstitial

23

What occurs in spiral artery conversion?

1) Loss of smooth muscle
2) Loss of endothelial lining

Causes ↑ dilation and loss of vasoactivity
This slows rate of inflow and ↓ pressure in intervillous space

24

What does the placenta need for effective exchange?

1) Stable low-pressure/high volume maternal blood supply
- Occurs following conversion of spiral arteries

2) Large surface area for exchange
- Terminal villi provide this

3) Transporter mechanisms

4) High placental gradient

25

What are the types of transplacental transport mechanisms

1) Diffusion
- Paracellular
- Tanscellular
- Gasses, FFAs and urea

2) Facilitated diffusion
- Requires carrier proteins example = GLUT
- No ATP
- Glucose, FFAs

3) Active transport
- ATP dependent
- Needed for amino acids (because fetal:maternal amino acids >1)

4) Receptor mediated endocytosis
- Only transports IgG
- Mainly occurs in last month of pregnancy → passive immunity

26

What are the 3 active transport systems for transporting amino acids?

All Na⁺ dependent

1) Systems A + ASC → neutral amino acid
2) Systems Xag → acidic amino acid
3) Systems L → neutral amino acid

27

What peptide hormones does the placenta synthesise?

"
"

28

What steroid hormones does the placenta synthesise?

"
"