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Development and Ageing > Foetal Growth and Placentation > Flashcards

Foetal Growth and Placentation Flashcards

1
Q

Describe early embryo nutrition with a word.

A

histiotrophic

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2
Q

Early embryo is reliant on what for nutrition?

A

uterine gland secretions and breakdown of endometrial tissues

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3
Q

At the start of the 2nd trimester, embryo switches from histiotrophic to ______ support.

A

haemotrophic

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4
Q

How is haemotrophic support achieved in humans?

A

through a haemochorial-type placenta where maternal blood directly contacts the fetal membranes

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5
Q

Define chorion.

A

outermost membrane surrounding an embryo

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6
Q

What is the connecting stalk?

A

links embryo to chorion

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7
Q

What are trophoblastic lacunae

A

Large spaces filled with maternal blood formed by breakdown of maternal capillaries and uterine glands
Become intervillous spaces aka maternal blood spaces

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8
Q

Define amnion.

A

innermost membrane that encloses the embryo

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9
Q

Define foetal membranes.

A

extraembryonic tissues that form a tough but flexible sac encapsulates the fetus and forms the basis of the maternal-fetal interface

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10
Q

The amnion arises from?

A

epiblast

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11
Q

The amnion goes on to form?

A

closed, avascular sac with developing embryo at one end

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12
Q

Amniotic sac is filled with?

A

amniotic fluid

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13
Q

Amniotic fluid is secreted from what week?

A

5th week

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14
Q

Functions of amniotic sac

A

encapsulates and protects the embryo

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15
Q

The chorion arises from?

A

yolk sac derivatives and the trophoblast

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16
Q

Is the chorion avascular or highly vascularised?

A

highly vascularised

17
Q

The chorion gives rise to?

A

chorionic villi

18
Q

What are chorionic villi?

A

outgrowths of cytotrophoblast from the chorion that form the basis of the fetal side of the placenta

19
Q

Amniotic sac is formed of what two layers?

A

amnion on the inside

chorion on the outside

20
Q

What is the allantois?

A

outgrowth of the yolk sac

21
Q

Allantois grows along?

A

connecting stalk from embryo to chorion

22
Q

Allantois goes on to?

A

becomes coated in mesoderm

vascularises to form umbilical cord

23
Q

Primary chorionic villi

A 
Cytotrophoblast forms
finger-like projections 
through 
syncitiotrophoblast layer
Into maternal
endometrium
24
Q

Function of chorionic villi

A

provide substantial surface area for exchange

25
Q

List the three phases of chorionic villi development.

A

primary
secondary
tertiary

26
Q

primary phase of chorionic development

A

outgrowth of the cytotrophoblast and branching of these extensions

27
Q

secondary phase of chorionic development

A

growth of the fetal mesoderm into the primary villi

28
Q

tertiary phase of chorionic development

A

growth of the umbilical artery and umbilical vein into the villus mesoderm, providing vasculature.

29
Q

Maternal blood supply to the endometrium

A

Uterine artery branches > network of arcuate arteries > radial arteries >
basal arteries form spiral arteries during menstrual cycle endometrial thickening

30
Q

Spiral artery remodelling

A

Extra-villus trophoblast (EVT) cells coating the villi invade down into the maternal spiral arteries, forming endovascular EVT.

Endothelium and smooth muscle is broken down – EVT coats inside of vessels

31
Q

How does the foetus get oxygen?

A

across placenta via diffusion (high maternal O2 tension, low fetal O2 tension)

32
Q

How does the foetus get glucose?

A

facilitated diffusion by transporters on maternal side and fetal trophoblast cells

33
Q

How does the foetus get water?

A

placenta main site of exchange, though some crosses amnion-chorion. Majority by diffusion, though some local hydrostatic gradients

34
Q

How does the foetus get electrolytes?

A

large traffic of sodium and other electrolytes across the placenta – combination of diffusion and active energy-dependent co-transport

35
Q

How does the foetus get calcium?

A

actively transported against a concentration gradient by magnesium ATPase calcium pump.

36
Q

How does the foetus get amino acids?

A

reduced maternal urea excretion and active transport of amino acids to foetus

37
Q

Maternal changes for maternal-foetal oxygen exchange

A

^CO 30% in 1st trimester, peripheral resistance decreases 30%, ^blood vol by 40%, ^ pulmonary ventilation 40%

38
Q

Compare O2 content and saturation of foetal and maternal blood.

A

similar

39
Q

Which has a greater affinity for O2: maternal haemoglobin or foetal haemoglobin?

A

foetal haemoglobin

Development and Ageing (9 decks)

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