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Human development block > Parturition &lactation > Flashcards

Parturition &lactation Flashcards

1
Q

Define parturition

A
  • Process of giving birth ‘to be in labour’
  • Involves softening & effacement of the cervix and development of uterine contractions( rupture of membranes not essential)
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2
Q

Outline the stages of labour

A
  1. ) INITIAL (LATENT) PHASE: Contractions develop, cervix softens &effaces (days)
  2. )ACTIVE PHASE: Regular contractions (~3 every 10mins) & steady dilation of the cervix (~3-4cm to 10cm)
  3. )STAGE 2: cervix fully dilated-10cm; strong propulsive contractions 1-2hours
  4. ) STAGE 3: placenta delivered (oxytocin important)
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3
Q

What else may be given to a woman if oxytocin is insufficient in delivering the placenta

A

-Clinically women may be given ergotocin & oxytocin mix to allow artificial contraction of the uterus in case the oxytocin is insufficient

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4
Q

Describe the quiescent stage of pregnancy

A

<37weeks

  • During this stage the cervix &membranes are intact
  • Closed cervix maintains pregnancy and acts as a barrier to ascending infection
  • The cervix is elastic tissue with some smooth muscle; collagen fibres in a proteoglycan matrix
  • There is also epithelia cell lining and a mucous plug
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5
Q

Outline the preparation of the cervix& fetal membranes for labour (activation and stimulation)

A

-PGE2 is used for induction. This causes membrane weakening and rupure, causing cervix ripening to begin and allowing the cervix to dilate
INFLAMMATORY PROCESS:
-iNOS, COX-2, prostaglandin production (PGE2), matrix metalloproteinases 2&9(these break down the collagen), cytokines and immune cells
-Cervix softens and more likely to dilate/efface; ready for labour

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6
Q

What instigates the inflammatory process?

A

Hormone changes: functional progesterone withdrawal—> inflammation &influx of immune cells,increased corticotrophin releasing hormone & oestrogen, plus cervical distension —> oxytocin—>PGR (Ferguson reflex)

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7
Q

How is the myometrium prepared for pregnancy?

A

-At the quiescent stage the myometrium is dense smooth muscle cells embedded in connective tissue & well vascularised. It is sparsely innervated in pregnancy
-To get to the activation / stimuation stage….
-There’s induction of ‘contraction associated proteins; prostaglandin receptor COX-2, oxyotcin receptor, gap junctions (connexins), calcium signalling proteins & ion channels
-Myometrium primed for contraction
-activation with some uterine activity
powerful effective contractions stimulate it

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8
Q

What causes preparation of the myometrium for pregnancy?

A
  • CRH
  • oestrogen
  • oxytocin
  • uterine distension
  • function progesterone withdrawal-inflammation &influx of immune cells
  • prostaglandins from the fetal membranes
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9
Q

What is Nifedipine used for in labour

A
  • used to treat pre-term labour

- It is an L-type ca2+ channel blocker so targets the voltage gated ca2+ channels to stop contraction

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10
Q

How does the contractile interval change during pregnancy?

A

-Decreases as the woman comes to term

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11
Q

How does the resting membrane potential change during pregnancy?

A

-Gets less negative so it’s more likely to be excited and more likely to contract at the end of pregnancy

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12
Q

What is the clinical application of PGE2?

A

-Used to ripen the cervix

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13
Q

Outline the functions of gap junctions& connexins in pregnancy

A

-Gap junctions made from connexin proteins(Cx)
-Cx43 & Cx26 up-regulated during labour—> allows for better transmission of signals between cells
Increased gap junctions results in:
-Intercellular communication
-More powerful contractions

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14
Q

Outline the role of oxytocin in labour

A
  • Important uterotonin in labour
  • Increased uterine sensitivity to oxytocin at term
  • Increased expression of oxytocin receptor mRNA & protein towards term and peak after onset of labour
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15
Q

Which hormone is thought to be the placental clock?

A
  • CRH

- As the placenta matures it starts pumping out CRH

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16
Q

Why must time of delivery be relatively tightly controlled?

A
  • Babies need to be born at the right time as if not the mother will no longer be able to provide adequate support
  • The placenta ages over time so there will be a risk of insufficient nutrients
  • All the babies are delivered by 42 weeks, as if not then medical intervention would result
17
Q

What initiates/times labour in humans ?

A
  • Fetal HPA axis involvement, but progesterone drop not apparent. Evidence for ‘functional’ progesterone withdrawal
  • Increasing oestrogen concentrations
  • Anecephaly& fetal adrenal gland hypoplasia association with prolonged gestation
18
Q

Describe the circulating placental steroid hormone levels during pregnancy in humans

A
  • Steady rise in Estradiol (E2) across gestation
  • Steady rise with plateau at term in progesterone
  • Steady rise in human placental lactogen
  • No decrease in progesterone at term
19
Q

Outline the Ferguson reflex(PGR)

A
  • A neuro-endocrine reflex
  • A +ve feedback mechanism involving oxytocin
  • Estrogen from ovaries–> Induces oytocin receptors on uterus—> stimulates placenta to make—> prostaglandins which stimulate more contractions of uterus—> positive feedback causing oxytocin release
  • Oxytocin from fetus and mother’s posterior pituitary stimulates the uterus to contract
  • Initiated by pressure at the cervix or vaginal walls
20
Q

List the important signals in human parturition

A

-Fetal hypothalamus activity increases–> increased CRH production–> increased ACTH production
-Fetal adrenal gland increases cortisol & dehydroepiandrosterone sulphate (DHEAS)
-Increased placental CRH & Estrogens
-Reduced progesterone responsiveness ( increased PRA:PRB ratio)
Inflammation:
-Fetal membranes increase COX-2 and increase prostaglandin production

21
Q

What is the function of DHEAS?

A
  • Can get over to the placenta

- Gets converted to oestrogen

22
Q

When do the lobules/alveoli grow for milk production

A
  • They grow during early pregnancy to make more milk-producing cells
  • Human alveoli adequately differentiated to produce milk from 16 weeks gestation & prolactin is being produced
  • But full lactation doesn’t occur until post partum period
23
Q

Outline how milk is pushed to the nipple

A

Milk production— Baby suckles— contraction of myoepithelial cells around the alveoli— pushes the milk to the nipple

24
Q

Describe the hormonal changes that occur at the onset of lactation

A
  • Prolactin is secreted from 16 weeks but breast tissue is unresponsive due to a steroid block
  • Withdrawal of oestrogen & progesterone are essential
  • Prolactin also drops (suppressed by oestrogen & progesterone) but a steady production maintained (if no suckling-small amount of milk produced 3-4weeks)
  • Suckling ensures prolactin secretion; full lactogenesis
25
Q

What is the link between prolactin & VIP

A

VIP is a prolactin releasing factor

26
Q

What is the link between prolactin & dopamine?

A

Dopamine is a prolactin inhibitory factor

27
Q

How does suckling ensure milk production?

A
  1. ) Neuroendocrine reflex
  2. ) Suckling:
    - Stimulates production of Vasoactive Intestinal Peptide
    - Reduces dopamine release
  3. ) Strength &duration of suckling determines amount of prolactin released from the anterior pituitary
    - This determines amount of milk made to be available for subsequent feeds
28
Q

Outline the milk ejection reflex

A
  • Milk is transported from alveoli to nipple
  • Neuroendocrine reflex
  • Suckling stimulates paraventricular & supraoptic nuclei to produce and release oxytocin (from posterior pituitary)
  • Oxytocin causes contraction of myoepithelia cells surrounding alveoli full of milk
  • Milk propelled into ducts and intramammary pressure builds up
  • Milk spurts through nipple
  • Response can be conditioned

Human development block (35 decks)

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