Physiology of parturition and lactation Flashcards
1
Q
partuition
A
process of giving birth
2
Q
what does partuition involve
A
softening and effacement of the cervix
development of uterine contractions
rupture of memebrane non essential
3
Q
softening and effacement of the cervix
development of uterine contractions
rupture of memebrane non essential
A
partuition
4
Q
what is the first stage of labour
A
initial latent phase
5
Q
initial latent phase
A
first stage of labour
- contractions develop and cervix softens across days
6
Q
what happens after initial latent phase
A
active phase
7
Q
active phase
A
reguar contractions ~3/10 minutes across hours
dilated between 3-10 cm
8
Q
stage 2 of labour
A
cervix fully dilated 10 cm
strong proulsive contractions across 1-2 hours
9
Q
fully dilated
A
10 cm, stage 2
10
Q
stage 3 of labour
A
placenta is delivered
oxytocin important
11
Q
quiescence
A
37 weeks build up to labour
12
Q
when are there no uterine contractions
A
quiescence
13
Q
what is activation of labour
A
physiological preparation for labour
14
Q
when does activationof labour occur
A
1-2 weeks prior
15
Q
closed cervix
A
maintains pregnancy
16
Q
softening of cervix
A
makes it more likely to dilate ready for labour
17
Q
role of cervix
A
barrier to infection
18
Q
what is the cervix
A
elastic tissue with some smooth muscle and collagen fibres in proteoglycan matrix
19
Q
what lines the cervix
A
epithelia cell and mucus plug which are immune cells to prevent infections from vaginal tract
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
21
Q
what doe matrix metalloproteinases 2 and 9 do
A
breakdown collagen to soften cervix
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
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
24
Q
what causes oxytocin release in parturition
A
cervical distention
25
COX-2
increased expression at term and post partum to breakdown collagen fibrils
bc COX2 produces prostaglandin
26
state of myometrium when not contracting
- dense smooth muscle cells embedded in connective tissue
- well vascularised
- sparsley innervated during pregnancy
27
state of myometrium when primed for contraction
- increased contraction associated proteins
28
contraction associated proteins
prostaglandin receptor, COX-2, oxytocin receptorm gap junctions, ion channels and calcium signalling proteins
29
what caues braxton hix
ion channels and calcium signalling proteins
30
PGE-2
prostaglandin E2 used to ripen cervix
31
what causes priming of myometrium
CRH, oestrogen, oxytocin and uterine distention
| functional progesterone withdrawal
32
what does functional prgesterone withdrawl cause
- inflammation and influx of immune cells
- production of prostaglandins from foetal memebranes
= helps prime myometrium
33
what is myometrium contraction dependent on
calcium
34
how is myometrium contraction augmented
use of agonists such as PGs or oxytocin
35
difference between sponateous and augmented contractions
augmented contractions are massive
36
how is labour induced at term
oxytocin
37
pro-relaxation
suppress pathways at labour onset
38
pro-contraction
activate pathways at labour onset
39
what effect does calcium have on contraction
an indirect effect
40
what are the changes in myometrial excitablilty and contractile activity during pregnancy
- frequency of contractions increases
- ion channel populations change from K to Ca
- resting membrane becomes less negative therefore more excitable
41
what are gap junctions made from
connexin proteins Cx
42
What happens to gap juctions in labour
Cx43 and Cx26 are upregulated to better transmission of signals between cells
43
why and when are Cx43 and Cx26 upregulated
in labour to better transmission between cells which makes contractions more powerful
44
how is uterine sensitivity to oxytocin increased and when
at term, there is increased expression of oxytocin receptor mRNA and protein and a peak expression after onset of labour
45
expression of COX isoforms in human myometrium throughout pregnancy
- upregulated prior to pregnancy
| - respoonsbile for cervix reipening by prostaglandin
46
what signalls to mother to prepare for birth
foetus signals to mother and produces hormones from HPA axis
47
What main hormone does placenta pump out in preparation for birth
CRH
48
What effect does CRH have, where and when released
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
is priming of tissues for contraction feed forward or feedback
feedforward
50
non hormonal signal for labour onset
uterine distention from baby growth
| cervical distention from baby movement
51
cervical distention
movement of baby towads cervic triggers neuroendocrine relfex as cervix is innovated
spinal chord reflex stimuates oxytocin production
52
uterine distention
- uterus starts diving and producing cells for growth
- once limit reached, uterus must stretch
- stretch signals labour onset
53
Ferguson reflex
spinal chrod reflex triggeredd by baby descending towards cervic which stimulates oxytocin production
54
normal time for birth
40 weeks
55
at what stage does birth become dangerous
42 weeks
56
dominant tissues for controlling birth timing
foetal HPA axis and placenta
57
balance of which hormones regualted timing of birth
progesterone:oestrogen
58
what does the balance of progesterone:oestrogen regulate
timing of birth
59
what initiates labour in animals
drop in progesterone mediated by foetal HPA axis
60
does progesterone drop in humans for initiating labour
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
what is the change in prgesterone for initiating labour
there is no change in progesterone levels
there is change in signalling/receptor progesterone
there is functional withdrawal of progesterone
62
what happens to oestrogen concentrations for initiating labour
increase
63
trigger for labour
not a single trigger but many contributory effects
64
why is labour initiation thought to be triggered by many contributing factors
it is an evolutionary sound strategy; many physiological events pushing towards labour until point of no return is reached and birth proceeds
65
what does primate uterine activity tell us about labour preparation
- slow development of contractions
- uterine contractions several nights before labour onset
- oxytocin spurt increase PGR
- humans report similar; false labour few days prior
66
what happens to oestrogen:prgesterone ratio in sheep
- Increased foetal cortisol & ACTHA
- Causes P450 hydroxylase to convert progesterone to oestrogen
- causes increased PG output
67
is progesterone converted to oestrogen in humans for labour onset
no, happens in sheep because they have P450 hydroxylase enzyme but humans do not
68
placental steroid hormones
oestradiol E2
| progesterone
69
what happens to placental steroid hormones levels during pregenacy
- steady rise in oestradiol
| - steady rise in progesterone with plateau at term
70
which placental steroid hormone platueas at term
progesterone
71
what is functional progesterone withdrawal
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
what allows lactation
growth of lobules/alveoli during pregnancy to make more milk-producing cells
73
nutrient content of mature human milk per litre
```
energy = 750 kcal
lipid = 38g
casein protein = 2.5g
whey protein = 6.4g
lactose = 70g
```
74
when are human alveoli adequately differentiated to produce milk
from 16 weeks of gestation BUT full lactation doesnt occur until post partum
75
when does full lactation occur
post partum
76
why doesn't full lactation occur at 16 weeks
prolactin is secreted but breat tissue is unresponsive becuase of steroid block
77
what allows full lactation
withdrawal of porgesterone and oestrogen, becuase they suppress prolactin
78
what happens to prolactin levels at birth
they drop but a steady production is still maintained as long as the baby suckles
79
without suckling, how long will prolactin be priduced
3-4 weeks in small amounts
80
what ensures prolactin secretion
suckling. Baby orders next meal. More suckling = more milk
81
full lactogenesis
= copius milk productin
82
how does suckling ensure milk production?
- neuroendocrine reflex with a 2-3 hour delay
| - strength and duratin determins amount of prolactin released
83
how does suckling stimulate milk production
stimulates production of vasoactive intestinal peptide VIP
| reduces dopamine release
84
where is milk stored
alveoli
85
VIP
vasoactive intestinal peptide
86
what increases prolaction
VIP - vasoactive intestinal peptide
87
what is VIP
prolactin releasing factor
88
what is the prolactin releasing factor
VIP
89
what inhibits prolactin
dopamine
90
dopamine effect on prolactin
inhibitory
91
how many different pathways are there for milk secretion
5
92
pathway I for milk secretion
exoctytotic secretion of milk proteins
| lactose, calcium and aq phase componenets
93
pathway II for milk secretion
milk fat secretion
| lipid droplets move to apical memerbane and secreted as membrane bound milk fat globule
94
pathway III for milk secretion
vesicular transcytosis
| immuoglobulins from the interstitial
95
pathway IV for milk secretion
transporters
| direct movement of monovalent ions, water & glucose across apical and basal membrane
96
pathway V for milk secretion
paracellular transport
| for plasma componenets and leukocytes that are bigger, open only during pregnancy, involution & inflammation
97
exoctytotic secretion of milk proteins
pathway I
| lactose, calcium and aq phase componenets
98
milk fat secretion
pathway II for milk secretion
| lipid droplets move to apical memerbane and secreted as membrane bound milk fat globule
99
vesicular transcytosis for milk secretion
pathway III for milk secretion
| immuoglobulins from the interstitial
100
transporters for milk secretion
pathway IV for milk secretion
| direct movement of monovalent ions, water & glucose across apical and basal membrane
101
paracellular transport for milk secretion
pathway V for milk secretion
| for plasma componenets and leukocytes that are bigger, open only during pregnancy, involution & inflammation
102
what rate does milk ejactulation relfex occur
immediately
103
what kind of reflex is milk ejactualtion
neuroendocrine
104
where does milk travel in ejactulaton
from alveoli to nipple
105
what stimulates milk ejaculation
suckling
106
how does suckling stimulate milk ejaculation
- stimulates paraventricular and supropic nuclei to produce and release oxytocin from prosterior pituitary
107
where is oxytocin released from in milk ejactulation
prosterior pituitary
108
when is oxytocin released
onset of labour and milk ejaculation
109
what effect does oxytocin have on milk ejaculation
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
what is special about eh milk ejaculatin response
can be conditioned
111
what is the let down reflex of milk ejaculation
milk ejaculation triggered by baby crying
