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

9.0 Placentation Flashcards

1
Q

What does the inner cell mass differentiate into?

A

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

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2
Q

What layer forms the extra-embryonic mesoderm?

A

Hypoblast

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3
Q

What are the two layers of extra-embryonic mesoderm?

A

1) Chorion (applied to inside of trophoblast)<br></br>2) Cell layers that covers outer surface of yolk sac and amnion<br></br><br></br>Extra-embryonic coelom is found in between the above two layers

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4
Q

When is the extra-embryonic coelom obliterated?

A

12 weeks<br></br>Amnion expansion → obliteration of extra-embryonic coelom

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5
Q

Features of the outer surface of yolk sac:

A

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

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6
Q

Functions of placenta:

A

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

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7
Q

What shape is the placenta?

A

Discoid

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8
Q

What is the diameter of the placenta?

A

20-25cm

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9
Q

What is the weight of the placenta?

A

400-600g

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10
Q

What are the two layers of the placenta?

A

<b>1) Choronic plate</b><br></br>- Facing fetus<br></br><br></br><b>2) Basal plate</b><br></br>- Facing decidua basalis

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11
Q

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

A

1) Syncytiotrophoblast (SCT)<br></br>- Multinucleated<br></br>- Non-proliferative<br></br><br></br>2) Cytotrophoblast (CTB)<br></br>- Deeper

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12
Q

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

A

STB → invade decidua → spaces form lacunae where maternal secretions and blood enter<br></br><br></br>CTB + extraembryonic mesoderm infiltrate trabeculae (in between lacunae) → placental villi

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13
Q

Where do stem villi arise from?

A

Chorionic plate

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14
Q

Where do anchoring villi connect to?

A

Basal plate

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15
Q

When do terminal villi form?

A

2nd 1/2 of gestation

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16
Q

What is the main nutrient source in histiotrophic nutrition?

A

Carbohydrate and lipid secretions from the endometrial glands<br></br><br></br>Glands are stimulated by progesterone from the corpus luteum

17
Q

When does haemotrophic nutrition start?

A

Week 12 of pregnancy

18
Q

What are the features of the embryonic period of pregnancy?

A
  • Histiotrophic nutrition<br></br>- Organogenesis<br></br>- Susceptible to malformation
19
Q

What are the features of the fetal period of pregnancy?

A
  • Haemotrophic nutrition<br></br>- Growth and functional maturation
20
Q

What is the surface area of the placental villous tree?

A

12-14m²

21
Q

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

A

Extravillous trophoblast cells

22
Q

How to EVT cells migrate to spiral arteries?

A

From tips of anchoring villi. Via 2 methods:<br></br>1) Endovascular<br></br>2) Interstitial

23
Q

What occurs in spiral artery conversion?

A

1) Loss of smooth muscle<br></br>2) Loss of endothelial lining<br></br><br></br>Causes ↑ dilation and loss of vasoactivity<br></br>This slows rate of inflow and ↓ pressure in intervillous space

24
Q

What does the placenta need for effective exchange?

A

<b>1) Stable low-pressure/high volume maternal blood supply</b><br></br>- Occurs following conversion of spiral arteries<br></br><br></br><b>2) Large surface area for exchange</b><br></br>- Terminal villi provide this<br></br><br></br><b>3) Transporter mechanisms</b><br></br><br></br><b>4) High placental gradient</b>

25
Q

What are the types of transplacental transport mechanisms

A

<b>1) Diffusion</b><br></br>- Paracellular<br></br>- Tanscellular<br></br>- Gasses, FFAs and urea<br></br><br></br><b>2) Facilitated diffusion</b><br></br>- Requires carrier proteins example = GLUT<br></br>- No ATP<br></br>- Glucose, FFAs<br></br><br></br><b>3) Active transport</b><br></br>- ATP dependent <br></br>- Needed for amino acids (because fetal:maternal amino acids >1)<br></br><br></br><b>4) Receptor mediated endocytosis</b><br></br>- Only transports IgG<br></br>- Mainly occurs in last month of pregnancy → passive immunity

26
Q

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

A

All Na⁺ dependent<br></br><br></br><b>1) Systems A + ASC</b> → neutral amino acid<br></br><b>2) Systems Xag</b> → acidic amino acid<br></br><b>3) Systems L</b> → neutral amino acid

27
Q

What peptide hormones does the placenta synthesise?

A

“<div><img></img></div>”

28
Q

What steroid hormones does the placenta synthesise?

A

“<div><img></img></div>”

MedST IB: Human Reproduction (HR) (13 decks)

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