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Human physiology > Reproduction 4 > Flashcards

Reproduction 4 Flashcards

1
Q

How long does pregnancy last?

A

40 weeks

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2
Q

What is parturition?

A

Birth

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3
Q

What is lactation?

A

Milk production in mammary glands

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4
Q

What are the stages of parturition?

A

Positioning of the fetus:
* Head-first on the cervix

At 37 weeks only 5% are still in feet-first position (breech):
* Half of these will ‘kick’ themselves around once labour start

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5
Q

How long does the first stage of labour last?

A

Up to 24 hours

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6
Q

What are the 2 main steps in the first stage of labour?

A
  • Dilation of the cervial canal to accomodate fetus
  • Inc myometrial contractions to exel the fetus - 30 min interval & 30s duration
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7
Q

What happens during dilation of the cervical canal to accomodate fetus (first stage of labour)?

A
  • 10 cm dilation of the cervix required to accommodate the head
  • As the fetus ‘bears down’ head-first on the cervix, amniotic sac is ruptured
  • ‘waters breaking’
  • serves to lubricate the cervical canal
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8
Q

What happens during the increasing myometrial contractions to expel the fetus (first stage of labour)?

A

(30 min interval and 30s duration)

  • Braxton-Hicks contractions increase in frequency and force during 3rd trimester
  • in 1st stage of labour the contractions become more coordinated and stronger
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9
Q

What happens in the second stage of labour?

A
  • 30-90 minutes duration
  • Cervical dilation is complete
  • Head of fetus activates cervical stretch receptors to synchronise abdominal and uterine contractions –>3 minute intervals, 60s duration
  • Baby is delivered connected to umbilical cord –> Cord is tied, then severed
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10
Q

What happens in the third stage of labour?

A
  • (30 min post-partum)
  • Second series of myometrial contractions expel the placenta - the ‘afterbirth’ —> continued contraction of the myometrium prevents excessive haemorrhage
  • loss of the placenta causes a major fall in maternal progesterone and estrogen levels
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11
Q

What is the main fetal response to parturition?

A

Inspiration of air following delivery, it has 2 concequences;

  • Elevated levels O2 in fetal circulation
  • Fetal supply of O2 to placental cirulation
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12
Q

What happens when levels of O2 in fetal circulation elevate in the fetal response to partuiton?

A

Increased production of vasoconstrictor prostanoids leads to closure of the ductus arteriosus

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13
Q

What happens to fetal supply of O2 to placental cirulation in the fetal response to partuition?

A

Induces prostanoid vasoconstriction of placental blood vessels - contributes to third stage of labour

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14
Q

What are the stages of parturition?

A

1 - End of pregnancy - cervix ripens

2 - Beginning of partuition –> cervix dilates, labour (uterine contractions)

3 - Babies head wedges cervix open - baby born head first

4 - Expulsion of placenta = afterbirth

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15
Q

Please look at the diagram on the regulation of partuition

A

It is a +ive feedback loop

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16
Q

What is known about the trigger for partuition?

A

Unkown, but current throty suggests signal comes from fetus

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17
Q

What are the triggers for partuition that are known?

A
  • Fetal placenta = CRH –> fetal ACTH –> DHEA
  • DHEA -> estrogens = Enters maternal blood stream
  • Estrogen -> parturition
18
Q

What is the role placental Cortiotophin Releasing Hormone (CRH)?

A
  • Regulate fetal adrenal production of DHEA sulphate and increases estrogen levels
  • Evidence for CRH receptors regulating sensitivity of myometrium to other agents
19
Q

When do placental levels of Cortiotophin Releasing Hormone (CRH) increase?

A

Placental levels increase during the pregnancy and levels at 16 weeks predicts duration

The placenta (and not the hypothalamus) is the principal source

20
Q

Descibre the pharmacology of pregnancy:

A
  • Uterine muscle characterised by high degree of spontaneous electrical and contractile activity
  • can be modified by humoral and neuronal factors
  • spread of excitation occurs via low resistance contacts (gap junctions) between cells - creates a functional syncitium
  • Therapeutic agents either increase intracellular calcium (spasmogen) or cyclic AMP (tocolytics)
21
Q

What is the role of spasmogens?

A

In force & frequency of contractions

22
Q

What are the spasmogens involved in birth & what do they do?

A

Oxytocin
* Given by slow infusion to titrate dose - intense contractions are sometimes precipitated which requires fetal monitoring

Prostaglandins F2∝ and E2
* Intravaginal tablets produce localised action which limits side effects - also used to ‘ripen’ cervix

23
Q

What are the slincal uses of spasmogens?

A
  • Induce or augment labour
  • Control post-partum uterine haemorrhage
  • Induce therapeutic abortion
24
Q

What sort of pregnancies are spasmogens used to induce?

A

Post-term pregnancies, near-term pre-eclampsia, active management of labour

25
Q

What do relaxants (Tocolytic agents) do?

A

Reduce freq & force of contractions

26
Q

What are the 2 types of relaxants (Tocolytic agents)?

A
  • β2-adrenoreceptor agonists
  • Magnesium ions
27
Q

When are β2-adrenoreceptor agonists used as relaxants (tocolytic agents)?

A
  • No evidence for differences between agonists
  • Contraindicated in women with heart disease and eclampsia and use with caution in diabetic mothers
28
Q

When are Magnesium ions agonists used as relaxants (tocolytic agents)?

A

Used in pre-eclampsia to alter cerebral blood flow and lower incidence and severity of condition

29
Q

What are the clinical uses of relaxants (tocolytic agents)?

A
  • Delay or prevent premature parturition –> up to 7 days
  • Slow or arrest delivery to undertake therapeutic measures
30
Q

What is used to inhibit lactation?

A
  • Estrogen
  • Progesterone
31
Q

What is used to stimulate lactation?

A
  • Prolactin
  • Oxytocin
32
Q

What are the 2 components of lactation?

A
  • Colostrum
  • Later milk
33
Q

What is colostrum?

A
  • Watery milk produced 1st few days after birth
  • Proteins, few nutrients
34
Q

What is later milk?

A

Nutrients, growth factors, hormones & antibodies

35
Q

Defo worth looking at the mammary glands diagram

A

Thanks

36
Q

What does prolactin stimulate?

A

Stimulates milk synthesis

37
Q

What does oxytocin stimulate?

A

Stimulates the milk ejection reflex

38
Q

Control of lactation diagram pls

A

Too complex to write on here

39
Q

What are the advantaegs of breast feeding for the mother?

A
  • Oxytocin release hastens uterine involution (around 4 weeks in lactating mother, 6 weeks otherwise)
  • Suckling surpresses menstrual cycle by inhibitn LH & FSH secretion
40
Q

How does suckling surpessing the mestrual cycle benefit the mother?

A
  • Acts as natural contraceptive (though not reliably!)
  • Directs mothers resources to newborn
41
Q

How does the cessation (stopping) of milk production at weaning happen?

A
  • Absence of suckling, prolactin secretion is not stimulated
  • No suckling leads to no oxytocin release –> therefore no milk letdown
  • Milk production does not immediately shut down, so pressure builds in alveoli (further stimulus to suppress milk production)
42
Q

How does the absence of suckling, leading to no stimulation for prolactin secretion cease milk production?

A

Removes the main stimulus for continued milk synthesis & secretion

Human physiology (43 decks)

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