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Development and Ageing > Parturition > Flashcards

Parturition Flashcards

1
Q

What does the pre natal circulatory system look like?

A
  • Placenta acts as site of gas exchange for fetus
  • Ventricles act in parallel rather than series (pump together)
  • vascular shunts bypass pulmonary & hepatic circulation -> close at birth
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2
Q

What does prenatal resp system look like

A
  • Primitive air sacs form in lungs around 20 weeks, vascularization from 28 weeks
  • Surfactant production begins around week 20, upregulated towards term
  • Fetus spends 1-4h/day making rapid respiratory movements during REM sleep* important for diapragm development and practice for air
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3
Q

What does Gastrointestinal system look like prenatally?

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
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4
Q

What does the nervous system look like prenatally?

A
  • Fetal movements begin late 1T, detectable by mother from ~14 weeks
  • Stress responses from 18 weeks, thalamus-cortex connections form by 24 weeks
  • Fetus does not show conscious wakefulness – mostly in slow-wave or REM sleep
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5
Q

What is labour?

A

Safe expulsion of fetus at the right time

expulasion of the placenta and fetal membranes too so it is empty for future

resolution/healing for future events

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6
Q

What increases in the fetal blood near the end of pregnancy?

A

Corticosteroids increase

Causes increase in liver glycogen and lecithin - surfactant. This spurs organ maturation ready for birth

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7
Q

How is labour a pro-inflammatory reaction?

A

Immune cell infiltration

Inflammatory cytokine and prostaglandin secretion

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8
Q

What is phase 1 of parturition?

A

Quiescence:

contractile, unresponsive, cervical softening

from late T1 onwards

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9
Q

What is phase 2 of parturition?

A

Activation:

uterine preparedness for labour, cervical ripening

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10
Q

What is phase 3 of parturition?

A

Stimulation:

uterine contraction, cervical dilation, fetal and placenta expulsion

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11
Q

What is phase 4 of parturition?

A

Involution:

recovery, uterine involution, cervical repair, breast feeding

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12
Q

What are the 3 stages of labour

different organisation method to the 4 phases

A

First stage: latent phase and active phase, contractions start

Second stage - commenced at full cervical dilation, maximal myometrial contractions

Third stage - explusion of placenta and membranes, post partum repair

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13
Q

What is the latent phase?

A

Slow dilation of the cervix to 2-3cm

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14
Q

What is the active phase?

A

Rapid dilation of cervix to 10cm

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15
Q

Which stage of labour is the longest?

A

Latent and active phase: 0-14 hours with active being longer

fetal descent and delivery in second phase taking 1-2 hours

placenta delivery taking 1 hour

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16
Q

How long is a first delivery?

A

8-18 hours

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17
Q

How long is subsequent deliveries?

A

5-12 hours

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18
Q

Why does the cervix need to have high connective tissue content?

A

provides rigidity

stretch resistant

connective tissue: bundles of collagen fibres embedded in proteo-glycan matrix

changes to the collagen bundle causes softening

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19
Q

How is the cervix remodelled?

A

Softening

Ripening:

Dilation

post partum repair

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20
Q

What is cervix softening?

A

Softening: in first trimester, changes in compliance but retains cervical COMPETENCE - keeps fetus in uterus

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21
Q

What is cervical ripening?

A

Weeks and days before birth the cervix will be:

  • infiltrated by monocyte and IL-6 and IL-8 secretion
    And Hylaluron deposition
22
Q

What is cervical dilation?

A

increased elasticity

  • increased hyluronidase expression –> HA breakdown

Matrix MatelloProteases decrease collagen content

23
Q

What is Post partum cervix repair?

A

Recovery of tissue integrity and competency

24
Q

How is labour initiated by corticotrophin released hormone (CRH)?

A

Fetus determines timing of parturition through changes in fetal HPA axis. And it releases CRH

CRH levels rise exponentially towards the end of pregnancy

There is a decline in CRH binding protein levels so CRH bioavailability increases

25
Q

What are the functions of CRH?

A

promotes fetal ACTH and cortisol release

increasing cortisol drives placental production of CRH –> positive feed back

stimulated DHEAS produced by the fetal adrenal cortex -> substrate for estrogen production

26
Q

What are DHEAS?

A

Dehydroepiandrosterone Sulphate - substrate to increase estrogen by the placenta

27
Q

What is progesterone important for?

A

maintains uterine relaxation throughout pregnancy

28
Q

Why may the estrogen progesterone ratio increase?

A

as serum estrogen:progesterone ratio may shift in favour of estrogen

29
Q

As term approaches how does progesterone decrease?

A

Switch from PR-A isoforms to PR-B and PR-C which are repressive isoforms

This causes Progesterone withdrawel * levels may be high but receptors have changed

30
Q

What happens to estrogen receptor Alpha expression during labour?

A

Rises

uterus becomes ‘blinded’ to progesterone action and sensitised to estrogen action.

31
Q

Where is oxytocin made?

A

a Nonapeptide hormone synthesised mainly in the utero-placental tissues and pituitary

32
Q

What drives Oxytocin expression increase in uterus?

A

Rise in estrogen levels

  • levels increase sharply at the onset of labour
33
Q

What promotes pituitary oxytocin release?

A

The Ferguson reflex:

promoted by stretch receptors

As fetus pushes down onto cervix, stretch receptors signal to hypothalamus trigers oxytocin release

34
Q

How does oxytocin signal?

A

Through G-coupled receptor (OTR/OXTR)

35
Q

What inhibits OXTR expression pre-labour?

A

Progesterone inhibits OXTR expression to keep the uterus relaxed

  • in comparison to estrogen which promotes large increase in uterine OXTR expression
36
Q

What are the functions of oxytocin?

A

increase connectivity of myocytes in myometrium

destablise membrane potentials to lower threshold for contraction

enhances liberation of intracellular Ca2+ ion stores to aid contraction

37
Q

What are the primary prostaglandins which are synthesized during labour?

A

PGE2, PGF2alpha and PGI2.

38
Q

How does estrogen levels drive prostaglandin action?

A

Rising estrogen activates phospholipase A2 enzyme, generating more arachidonic acid for PG synthesis

  1. Estrogen stimulation of oxytocin receptor expression promotes PG release.
39
Q

What does PGE2?

A

Cervix remodelling:

leukocyte infiltration - IL-8 release and collagen bundle re-modelling

40
Q

What does PGF2 Alpha do?

A

Acts on myometrium, destablise membrane potentials and connectivity of myocytes

41
Q

What does PGI2 do?

A
  • myometrium

Promotes myometrial smooth muscle relaxation and relaxation of lower uterine segment.

42
Q

What other factors may be involved in cervix re modelling?

A

peptide hormone relaxin and nitric oxide (NO)

43
Q

How does myometrial contractions lead to cervix to be pulled up to form the birth canal?

A

Myometrial muscle cells form a syncytium (gap junction)

contractions start from the fundas and work down the upper segement

muscle contractions are brachystatic causing lower segment and cervix to be pulled up to form birth canal

44
Q

What is brachystatis contractions?

A

fibres do not return to full length on relaxation

45
Q

How is the fetus expelled? *in what order

A

head engages with pelvic space

pressure on fetus causes chin to press against chest - flexion

fetus rotates so the belly is towards mothers spine

head expelled first after cervix dilates

shoulders delivered sequentially

46
Q

What shrinks rapidly after birth?

A

Uterus –> causea area of contact of placenta with endometrium to shrink

uterine shrinkage also causes folding of fetal membranes which then peel off the endometrium

47
Q

What does umbilical cord clamping do?

A

Stops fetal blood flow to placenta –> villi collapse

48
Q

How are the placenta and fetal tissues expelled?

A

Contractions

49
Q

what forms between the decidua and placenta?

A

Hematoma

50
Q

why does the uterus remain contracted post delivery?

A

facilitate uterine vessel thrombosis

51
Q

Why is it vital for uterus involution and cervix repair to occur?

A

Go back to non pregnant state

To shield uterus from commensural bacteria

restore endometrial cyclicity in response to hormones

Development and Ageing (5 decks)

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