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Endocrinology & Reproduction > Physiology of parturition and lactation > Flashcards

Physiology of parturition and lactation Flashcards

1
Q

partuition

A

process of giving birth

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2
Q

what does partuition involve

A

softening and effacement of the cervix
development of uterine contractions
rupture of memebrane non essential

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3
Q

softening and effacement of the cervix
development of uterine contractions
rupture of memebrane non essential

A

partuition

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4
Q

what is the first stage of labour

A

initial latent phase

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5
Q

initial latent phase

A

first stage of labour

- contractions develop and cervix softens across days

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6
Q

what happens after initial latent phase

A

active phase

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7
Q

active phase

A

reguar contractions ~3/10 minutes across hours

dilated between 3-10 cm

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8
Q

stage 2 of labour

A

cervix fully dilated 10 cm

strong proulsive contractions across 1-2 hours

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9
Q

fully dilated

A

10 cm, stage 2

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10
Q

stage 3 of labour

A

placenta is delivered

oxytocin important

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11
Q

quiescence

A

37 weeks build up to labour

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12
Q

when are there no uterine contractions

A

quiescence

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13
Q

what is activation of labour

A

physiological preparation for labour

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14
Q

when does activationof labour occur

A

1-2 weeks prior

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15
Q

closed cervix

A

maintains pregnancy

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16
Q

softening of cervix

A

makes it more likely to dilate ready for labour

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17
Q

role of cervix

A

barrier to infection

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18
Q

what is the cervix

A

elastic tissue with some smooth muscle and collagen fibres in proteoglycan matrix

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19
Q

what lines the cervix

A

epithelia cell and mucus plug which are immune cells to prevent infections from vaginal tract

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20
Q

what causes sofetning of the cervic

A

inflammation

  • increase in iNOS and COX-2
  • increase in prostaglandin
  • increase in matrix metalloproteinases 2 and 9, cytokines and immune cells
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21
Q

what doe matrix metalloproteinases 2 and 9 do

A

breakdown collagen to soften cervix

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22
Q

inflammation

  • increase in iNOS and COX-2
  • increase in prostaglandin
  • increase in matrix metalloproteinases 2 and 9, cytokines and immune cells
A

causes cervix softening

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23
Q

what causes inflammatory response for cervix softening

A

hormonal changes

  • functional progesterone withdrawal
  • inflammation and influx of immune cells
  • fetal HPA
  • placental CRH
  • oestrogen
  • oxytocin
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24
Q

what causes oxytocin release in parturition

A

cervical distention

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25
Q

COX-2

A

increased expression at term and post partum to breakdown collagen fibrils
bc COX2 produces prostaglandin

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26
Q

state of myometrium when not contracting

A
  • dense smooth muscle cells embedded in connective tissue
  • well vascularised
  • sparsley innervated during pregnancy
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27
Q

state of myometrium when primed for contraction

A
  • increased contraction associated proteins
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28
Q

contraction associated proteins

A

prostaglandin receptor, COX-2, oxytocin receptorm gap junctions, ion channels and calcium signalling proteins

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29
Q

what caues braxton hix

A

ion channels and calcium signalling proteins

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30
Q

PGE-2

A

prostaglandin E2 used to ripen cervix

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31
Q

what causes priming of myometrium

A

CRH, oestrogen, oxytocin and uterine distention

functional progesterone withdrawal

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32
Q

what does functional prgesterone withdrawl cause

A
  • inflammation and influx of immune cells
  • production of prostaglandins from foetal memebranes
    = helps prime myometrium
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33
Q

what is myometrium contraction dependent on

A

calcium

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34
Q

how is myometrium contraction augmented

A

use of agonists such as PGs or oxytocin

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35
Q

difference between sponateous and augmented contractions

A

augmented contractions are massive

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36
Q

how is labour induced at term

A

oxytocin

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37
Q

pro-relaxation

A

suppress pathways at labour onset

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38
Q

pro-contraction

A

activate pathways at labour onset

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39
Q

what effect does calcium have on contraction

A

an indirect effect

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40
Q

what are the changes in myometrial excitablilty and contractile activity during pregnancy

A
  • frequency of contractions increases
  • ion channel populations change from K to Ca
  • resting membrane becomes less negative therefore more excitable
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41
Q

what are gap junctions made from

A

connexin proteins Cx

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42
Q

What happens to gap juctions in labour

A

Cx43 and Cx26 are upregulated to better transmission of signals between cells

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43
Q

why and when are Cx43 and Cx26 upregulated

A

in labour to better transmission between cells which makes contractions more powerful

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44
Q

how is uterine sensitivity to oxytocin increased and when

A

at term, there is increased expression of oxytocin receptor mRNA and protein and a peak expression after onset of labour

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45
Q

expression of COX isoforms in human myometrium throughout pregnancy

A
  • upregulated prior to pregnancy

- respoonsbile for cervix reipening by prostaglandin

46
Q

what signalls to mother to prepare for birth

A

foetus signals to mother and produces hormones from HPA axis

47
Q

What main hormone does placenta pump out in preparation for birth

A

CRH

48
Q

What effect does CRH have, where and when released

A

released from placenta during preparation for labour and signals for tissue changes

  • functional progesterone withdrawal
  • increase in PG
  • changes in oestreogen to activate tissues
  • inflammatory response and more PG
49
Q

is priming of tissues for contraction feed forward or feedback

A

feedforward

50
Q

non hormonal signal for labour onset

A

uterine distention from baby growth

cervical distention from baby movement

51
Q

cervical distention

A

movement of baby towads cervic triggers neuroendocrine relfex as cervix is innovated
spinal chord reflex stimuates oxytocin production

52
Q

uterine distention

A
  • uterus starts diving and producing cells for growth
  • once limit reached, uterus must stretch
  • stretch signals labour onset
53
Q

Ferguson reflex

A

spinal chrod reflex triggeredd by baby descending towards cervic which stimulates oxytocin production

54
Q

normal time for birth

A

40 weeks

55
Q

at what stage does birth become dangerous

A

42 weeks

56
Q

dominant tissues for controlling birth timing

A

foetal HPA axis and placenta

57
Q

balance of which hormones regualted timing of birth

A

progesterone:oestrogen

58
Q

what does the balance of progesterone:oestrogen regulate

A

timing of birth

59
Q

what initiates labour in animals

A

drop in progesterone mediated by foetal HPA axis

60
Q

does progesterone drop in humans for initiating labour

A

there is no apparent drop in progesterone, although foetal HPA aixs is involved
there is eveidence for functional progesterone withdrawal and there is a changed in progesterone receptor/signalling

61
Q

what is the change in prgesterone for initiating labour

A

there is no change in progesterone levels
there is change in signalling/receptor progesterone
there is functional withdrawal of progesterone

62
Q

what happens to oestrogen concentrations for initiating labour

A

increase

63
Q

trigger for labour

A

not a single trigger but many contributory effects

64
Q

why is labour initiation thought to be triggered by many contributing factors

A

it is an evolutionary sound strategy; many physiological events pushing towards labour until point of no return is reached and birth proceeds

65
Q

what does primate uterine activity tell us about labour preparation

A
  • slow development of contractions
  • uterine contractions several nights before labour onset
  • oxytocin spurt increase PGR
  • humans report similar; false labour few days prior
66
Q

what happens to oestrogen:prgesterone ratio in sheep

A
  • Increased foetal cortisol & ACTHA
  • Causes P450 hydroxylase to convert progesterone to oestrogen
  • causes increased PG output
67
Q

is progesterone converted to oestrogen in humans for labour onset

A

no, happens in sheep because they have P450 hydroxylase enzyme but humans do not

68
Q

placental steroid hormones

A

oestradiol E2

progesterone

69
Q

what happens to placental steroid hormones levels during pregenacy

A
  • steady rise in oestradiol

- steady rise in progesterone with plateau at term

70
Q

which placental steroid hormone platueas at term

A

progesterone

71
Q

what is functional progesterone withdrawal

A

receptors change, not levels of P

  • increase in nuclear PRA:PRB
  • altered co-expression and activators effeting PR mediated transcription
  • PR transciprption blocked by NF-kB
72
Q

what allows lactation

A

growth of lobules/alveoli during pregnancy to make more milk-producing cells

73
Q

nutrient content of mature human milk per litre

A 
energy = 750 kcal
lipid = 38g
casein protein = 2.5g
whey protein = 6.4g
lactose = 70g
74
Q

when are human alveoli adequately differentiated to produce milk

A

from 16 weeks of gestation BUT full lactation doesnt occur until post partum

75
Q

when does full lactation occur

A

post partum

76
Q

why doesn’t full lactation occur at 16 weeks

A

prolactin is secreted but breat tissue is unresponsive becuase of steroid block

77
Q

what allows full lactation

A

withdrawal of porgesterone and oestrogen, becuase they suppress prolactin

78
Q

what happens to prolactin levels at birth

A

they drop but a steady production is still maintained as long as the baby suckles

79
Q

without suckling, how long will prolactin be priduced

A

3-4 weeks in small amounts

80
Q

what ensures prolactin secretion

A

suckling. Baby orders next meal. More suckling = more milk

81
Q

full lactogenesis

A

= copius milk productin

82
Q

how does suckling ensure milk production?

A
  • neuroendocrine reflex with a 2-3 hour delay

- strength and duratin determins amount of prolactin released

83
Q

how does suckling stimulate milk production

A

stimulates production of vasoactive intestinal peptide VIP

reduces dopamine release

84
Q

where is milk stored

A

alveoli

85
Q

VIP

A

vasoactive intestinal peptide

86
Q

what increases prolaction

A

VIP - vasoactive intestinal peptide

87
Q

what is VIP

A

prolactin releasing factor

88
Q

what is the prolactin releasing factor

A

VIP

89
Q

what inhibits prolactin

A

dopamine

90
Q

dopamine effect on prolactin

A

inhibitory

91
Q

how many different pathways are there for milk secretion

A

5

92
Q

pathway I for milk secretion

A

exoctytotic secretion of milk proteins

lactose, calcium and aq phase componenets

93
Q

pathway II for milk secretion

A

milk fat secretion

lipid droplets move to apical memerbane and secreted as membrane bound milk fat globule

94
Q

pathway III for milk secretion

A

vesicular transcytosis

immuoglobulins from the interstitial

95
Q

pathway IV for milk secretion

A

transporters

direct movement of monovalent ions, water & glucose across apical and basal membrane

96
Q

pathway V for milk secretion

A

paracellular transport

for plasma componenets and leukocytes that are bigger, open only during pregnancy, involution & inflammation

97
Q

exoctytotic secretion of milk proteins

A

pathway I

lactose, calcium and aq phase componenets

98
Q

milk fat secretion

A

pathway II for milk secretion

lipid droplets move to apical memerbane and secreted as membrane bound milk fat globule

99
Q

vesicular transcytosis for milk secretion

A

pathway III for milk secretion

immuoglobulins from the interstitial

100
Q

transporters for milk secretion

A

pathway IV for milk secretion

direct movement of monovalent ions, water & glucose across apical and basal membrane

101
Q

paracellular transport for milk secretion

A

pathway V for milk secretion

for plasma componenets and leukocytes that are bigger, open only during pregnancy, involution & inflammation

102
Q

what rate does milk ejactulation relfex occur

A

immediately

103
Q

what kind of reflex is milk ejactualtion

A

neuroendocrine

104
Q

where does milk travel in ejactulaton

A

from alveoli to nipple

105
Q

what stimulates milk ejaculation

A

suckling

106
Q

how does suckling stimulate milk ejaculation

A
  • stimulates paraventricular and supropic nuclei to produce and release oxytocin from prosterior pituitary
107
Q

where is oxytocin released from in milk ejactulation

A

prosterior pituitary

108
Q

when is oxytocin released

A

onset of labour and milk ejaculation

109
Q

what effect does oxytocin have on milk ejaculation

A

causes contraction of myoepithelia cells surrounding the alveoli full of milk so milk is propelled into ducts and the intramammary pressure builds forcing milk out of nipple

110
Q

what is special about eh milk ejaculatin response

A

can be conditioned

111
Q

what is the let down reflex of milk ejaculation

A

milk ejaculation triggered by baby crying

Endocrinology & Reproduction (15 decks)

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