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BRS 1: Development & Aging Domain > 3: Pregnancy parturition and late fetal development > Flashcards

3: Pregnancy parturition and late fetal development Flashcards

1
Q

Early embryo nutrition is

A

histiotrophic - reliant on uterine gland secretions and breakdown of endometrial tissues

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2
Q

When does embryo growth switch from histiotrophic to haemotrophic

A

start of 2nd trimester
- achieved through a haemochorial-type placenta where maternal blood contacts the foetal membrane

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3
Q

Fetal membrans

A

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

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4
Q

Aminion (inner fetal membrane)

A

arises from epiblast (doesn’t contribute to fetal tissues)
forms closed, avascular sac with developing embryo at one end
begins to secrete amniotic fluid from 5th week - forms fluid filled sac that encapsulates and protects fetus

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5
Q

Chorion (outer fetal membranee)

A

formed from yolk sac derivatives and trophoblast
highly vascularised
gives rise to chorionic villi

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6
Q

Allantois

A

outgrowth from yolk sac
grow along connecting stalk from embryo to chorion
becomes coated in mesoderm and vascularises to form umbilical chord

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7
Q

How is the amniotic sac formed

A

Expansion of amniotic sac by fluid accumulation forces amnion into contact with chorion, which fuse forming amniotic sac

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8
Q

Amniotic sac

A

sac 2 layers
amnion on inside
chorion on outside

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9
Q

Chorionic villi

A

outgrowths of cytotrophoblast from chorion that form basis of fetal side of placenta
- cavity formed, coated by mesoderm then blood vessels inside cavity (primary secondary and tertiary chorionic vili)

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10
Q

Terminal villus

A

convoluted knot of vessels and vessel dilation
slows blood flow - enabling exchange between maternal and fetal blood
whole structure coated with trophoblast

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11
Q

Terminal vilus in early pregnancy

A

150-200 micro meters in diameter
approx. 10 micrometer trophoblast thickness between cappilaries and maternal blood

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12
Q

Terminal vilus in late pregnancy

A

villi thin to 40 micro meters
vessels move within villi to leave only 1-2 micro meters trophoblast separation from maternal blood

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13
Q

Maternal blood supply

A

Uterine artery - gives rise to network of arcuate arteries
Radial artery - branch from arcuate arteries and branch further to form:
Basal artery - form spiral arteries during menstrual cycle endometrial thickening

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14
Q

How is oxygen transferred from the mother to the fetus

A

Diffusional gradient (high maternal O2 tension, low fetal O2 tension)

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15
Q

How is glucose transferred from the mother to the fetus

A

facilitated diffusion by transporters on maternal side and fetal trophoblast cells

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16
Q

How is water transferred from mother to fetus

A

Placenta - main exchange site
some crosses amnion-chorion
majority by diffusion, but some local hydrostatic gradients present

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17
Q

How are electrolytes transferred from mother to fetus

A

Large traffic of sodium + electrolytes across placenta
combination of diffusion and active energy-dependent co-transport

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18
Q

How is calcium transferred from mother to fetus

A

actively transported against concentration gradient by magnesium ATPase calcium pump

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19
Q

How are amino acids transferred from mother to fetus

A

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

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20
Q

What is organ formation in late fetal development driven by

A

corticosteroids

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21
Q

fetal circulatory system

A

placenta acts as a site of gas exchange
ventricles act in parallel rather than series
vascular shunts bypass pulmonary and hepatic circulation –> close at birth

22
Q

Fetal respiratory system

A

Primitive air sacs form in lungs around 20 weeks - vascularisation from 28 weeks
Surfactant production begins around week 20, upregulated towards term
fetus spends 1-4h/day making rapid respiratory air movements during REM sleep

23
Q

Fetal gastrointestinal system

A

endocrine pancreas functional from start of 2T, insulin from mid-2T
liver glycogen progressively deposited -accelerates towards term
large amounts of amniotic fluid swallowed - debris and bile acids form meconium

24
Q

Fetal nervous system

A

Fetal movements begin late 1T
detectable by moth from ~14 weeks
Stress response from 18 weeks, thalmus-cortex connections form by 24 weeks
Fetus doesn’t show conscious wakefulness - mostly in slow-wave or REM sleep

25
Q

Labour has the characteristics of a

A

pro-inflammatory reaction :
- immune cell infiltration
- inflammatory cytokine and prostaglandin secretion

26
Q

Stages of labour

A

Phase 1 - quiescence
Phase 2 - activation
Phase 3 - stimulation
Phase 4 - involution

27
Q

In the first stage of labour:

A

contraction starts
cervix dilates
extensive - 14h
latent phase - slow dilation of cervix too 2-3cm
active phase - rapid dilation of cervix to 10cm

28
Q

In the second stage of labour:

A

Delivery of fetus
Relatively quick 1/2hrs
- commences at full dilation of cervix (10cm)
- maximal myometrial contractions - intense and frequent

29
Q

In the third stage of labour:

A

Delivery of placenta
Expulsion of placenta and fetal membranes
Post-partum repair

30
Q

Process of cervix remodelling

A

Softening
Ripening
Dilation
Post-partum repair

31
Q

Softening of cervix

A

begins in first trimester
- measurable changes in compliance but retains cervical competency - remains close, keeps fetus in uterus

32
Q

Ripening of cervix

A

weeks and days before birth
- monocyte infiltration and IL-6 and IL-8 secretion
-Hylaluron deposition

33
Q

Dilation of cervix

A

increased elasticity
Increased hylaluronidase expresssion –> HA broken down
MMPs (matrix metalloproteinases) decrease collagen content

34
Q

Post partum repair of cervix

A

Recovery of tissue integrity and competency

35
Q

Role of cervix

A

retaining fetus in uterus

36
Q

Characteristics of cervix

A

Highly connective tissue content - provides rigidity, stretch resistant
Bundles of collagen fibres embededded in proteo-glycan matrix
Changes to collagen bundle structure underline softening - unclear mechanism

37
Q

Functions of CHR in labour

A
  • promotes fetal ACTH and cortisol release - incr. cortisol drives placental production of CRH = positive feedback
  • stimulates DHEAS production by the fetal adrenal cortex = substrate for oestrogen production
38
Q

CHR and initiation of labour

A
  • fetus determines timing of parturition through changes in fetal HPA axis
    Corticotrophin Releasing Hormone (maternal) levels rise exponentially towards end of pregnancy
    Decline in CRH-binding protein levels, so bioavailable (free to signal) CRH increases
39
Q

Progesterone levels during pregnancy

A

High progesterone - maintains relaxation

40
Q

Porgesterone and oestrogen levels as term approaches

A

progesterone receptors expressed by uterus switch from active signalling forms (PR-A) to repressive isoforms (PR-B and PR-C) isoforms
causing functional progesterone withdrawal

Rise in estrogen receptor alpha expression

41
Q

Progesterone and oestrogen levels during labour

A

uterus unresponsive to progesterone action and sensitized to oestrogen
likely leads to local changes in oestrogen-to-progesterone (E:P) ratio in uterine tissues

42
Q

Primary prostoglandings synthesised during labour

A

PGE2
PGF2alpha
PGI2

43
Q

How does rising oestrogen levels drive prostaglandin action in the uterus

A
  1. Rising estrogen activates phospholipase A2 enzyme, generating more arachidonic acid for PG synthesis
  2. Estrogen stimulation of oxytocin receptor expression promotes PG release
44
Q

PGE2

A

cervix re-modelling
- promotes leukocyte infiltration into cervix
IL-8 release and collagen bundle re-modelling allow softening of cervix and cervix ripening

45
Q

PGF2alpha

A

myometrial contractions
- destabilises membrane potentials and promotes connectivity of myocytes (with Oxytocin), mainly acts on myometrium

46
Q

PGI2

A

myometrium
promotes myometrial sooth muscle relaxation and relaxation of lower uterine segment
important between myometrial contraction for there to be relaxation for blood flow to uterus to provide fetus

47
Q

Other factors affecting labour

A

peptide hormone - relaxin (cervix re-modelling)
nitric oxide (NO) - implicated in cervix re-modelling

48
Q

Foetal explusion

A

Head engages with pelvic space 34-38 weeks
Pressure on fetus causes chin to press against chest (flexion)
fetus rotates (belly to mothers spine)
head expelled first after cervix dilation
shoulders delivered sequentially (upper first) followed by torso

49
Q

Post fetal delivery

A

rapid shrinkage of uterus - causes area of contact of placenta with endometrium to shrink
- shrinkage causes folding of fetal membranes - peel off the endometrium
- clamping of umbilical chord stops fetal blood flow to placeta = villi collapse
-Hematoma formation between decidua and placenta
-contractions expel placenta and fetal tissues

50
Q

Why does the uterus remain contracted after delivery

A

to facilitate uterine vessel thrombosis

51
Q

Process of uterine involution and cervix repair

A

restores non- pregnant state
- sheilding uterus from commensural bacteria
-restore endometrial cyclicity in response to hormones - allow future implantation

BRS 1: Development & Aging Domain (4 decks)

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