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3002 > 86 Uterine motility > Flashcards

86 Uterine motility Flashcards

1
Q

What are the 3 layers of the uterine wall?

A
  1. Perimetrium (serosa):
    • Single thin outer layer of epithelium, not evident clinically
  2. Myometrium:
    • Thick middle layer of smooth muscle
  3. Endometrium:
    • Inner layer with glands, blood vessels, lymphatics and epithelial cells
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2
Q

Function of gap junctions in uterine motility?

A
  • Uterine contractions depend on gap junctions for phasic propagation of depolarisation
  • Gap junctions - functional connection between adjacent muscle cells
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3
Q

What makes up gas junctions?

A

Connexin 43

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4
Q

Hormones influence which 3 events in uterine motility?

A
  1. Menstrual cycle
  2. Pregnancy
  3. Labour

Minimal influence of autonomic innervation on contractions under physiological conditions

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5
Q

Intercalated discs

A

Provide structural support to adjacent cells

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6
Q

Connexin structure

A
  • Transmembrane proteins
  • 6 connexins = connexon
  • Makes up the pore for a gap junction between the cytoplasm of two adjacent cells.
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7
Q

At which 3 sites in your body are gap junctions found?

A
  1. Cardiac muscle
  2. Vascular/ intestinal smooth muscle
  3. Uterine smooth muscle
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8
Q

Gap junctions in cardiac muscle?

A

• Constitutively expressed
• Arranged in intercalated discs
• Depolarisation starts from the sinoatrial (SA) node
(pacemaker)

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9
Q

Gap junctions in vascular/ intestine smooth muscle?

A
  • Constitutively expressed

* Not concentrated in specialised areas (exception of myenteric interstitial cell of Cajal)

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10
Q

Gap junctions in uterine smooth muscle?

A
  • Inducible (especially hormonally)

* Fundal dominance during labour may arise from anatomical arrangement of expressed gap junctions

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11
Q

Connexin 43 expression

A

(Uterus of pregnant rats)
• Immunofluoroescence is absent day 4
Evident day 14
Prominent day 20 (term in rat)

• Disappears postnatally

I.e. more gap junctions and connexins when they are physiologically needed, i.e. end of pregnancy

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12
Q

Innervation of the uterus?

A

• Sympathetic, parasympathetic and sensory

• Innervation of vascular smooth muscle and
myometrium

• Sympathetic outflow effect depends on receptor type:

  1. a-adrenoceptors: contraction
  2. b-adrenoceptors: relaxation

• Ratio of sympathetic receptor types influenced by hormonal status.

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13
Q

Posterior pituitary hormones?

A
  1. Antidiuretic hormone (ADH)/vasopressin (primarily acts on kidneys)
  2. Oxytocin
  • Both 9 amino acid peptides, 2 amino acids different
  • Both stimulate CONTRACTION of the uterus
  • Oxytocin receptor numbers are influenced by sex hormone levels
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14
Q

Oxytocin

A

• Posterior pituitary hormone

• At term:
– Falling placental progesterone with sustained oestrogen levels.
–> Stimulates prostaglandin biosynthesis
–> Oxytocin receptor expression

  • Uterine smooth muscle sensitive prior onset of labour
  • Stimulates increasingly regular, co-ordinated contraction that travel from fundus to the cervix (fundal dominance)
  • Uterus relaxes completely between contractions
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15
Q

Uterine stimulants (oxytocics) role?

A

• Induce abortion
• Induce and accelerate labour
• Contract the uterus after delivery to control postpartum
haemorrhage (PPH)

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16
Q

Uterine relaxants (tocolytics) role?

A
  • (Treat menstrual cramps/dysmenorrhoea).
  • Prevent or treat preterm labour
  • Facilitate obstetric manoeuvres
  • Counteract (iatrogenic) uterine hyperstimulation
17
Q

What are drugs which stimulate uterine contractions called?

A

Oxytocics

18
Q

Options for administrating uterine stimulants (oxytocics)

A
  1. Oxytocin:
    • IV infusion to induce or accelerate labour
    • IV or IM injection after delivery to control postpartum
    haemorrhage (PPH)
  2. Ergometrine
  3. E & F series prostaglandins
19
Q

Name 3 alkaloids

A
  1. Ergotamine
  2. Dihydro-ergotamine
  3. Ergometrine
20
Q 
Ergometrine:
• 5-HT receptor?
• alpha-adrenoreceptor?
• Dopamine receptor?
• Uterine contraction?
• Main uses?
A
  • 5-HT receptor: Antagonist/partial agonist
  • Alpha-adrenoreceptor: Weak antagonist/partial agonist
  • Dopamine receptor: Weak
  • Uterine contraction: +++
  • Main uses: Obstetric haemorrhage
21
Q

Uses of ergometrine in practice?

A
  • Useful for bleeding related to early pregnancy complications e.g. miscarriage
  • Causes sustained powerful uterine contractions
  • Largely obsolete for postpartum haemorrhage (PPH) prophylaxis owing to stability, inadvisability in the presence of hypertension (vasoconstriction), adverse effect of nausea/vomiting
22
Q

What is syntometrine?

A
  • Combination of oxytocin + ergometrine

* For 3rd stage of labour

23
Q

Prostaglandins’ role in pregnancy?

A
  • Endometrium/ decidua and myometrium have significant prostaglandin synthesising capacity
  • Membrane phospholipid substrate in late pregnancy
  • Prostaglandin F2a (PGF2a) generated in large amounts
  • Prostaglandin I2 (PGI2)/prostacyclin and prostaglandin E2 (PGE2) also occur naturally
  • F series more vasoconstrictor, E series vasodilator, both act on cervical ripening and induce oxytocin receptors
24
Q

Name 4 examples of prostaglandin drugs?

A
  1. Dinoprostone
    • Equivalent to prostaglandin E2 (PGE2), naturally occurring
  2. Carboprost
    • Synthetic analogue of prostaglandin F2a (PGF2a)
  3. Gemeprost
    • Synthetic analogue of prostaglandin E1 (PGE1)
  4. Misoprostol
    • Synthetic analogue of prostaglandin E1 (PGE1)
25
Q

What is misoprostol?
Uses?
Administration?

A

(PGE1 analogue)
• Room temperature storage
• Treatment/ prevention of peptic ulcers (initially)
• Medical abortion, myometrium sensitised by mifepristone
(progesterone receptor antagonist) then misoprostol
• Induction of labour
• Control of postpartum haemorrhage (PPH) secondary to uterine atony (not as effective as IV/IM oxytocin)
• Oral, vaginal, sublingual or rectal routes of administration

26
Q

What are the 5 categories of uterine relaxants (tocolytics)?

A
  1. Beta 2-agonists
  2. Calcium channel blockers
  3. Nonsteroidal anti-inflammatory drugs (NSAIDs)
  4. Oxytocin receptor antagonist
  5. Nitrates
27
Q

Beta 2-agonists as uterine relaxants (tocolytics):
• Name 3 examples
• Mechanism
• Side effects

A
  • Ritodrine, terbutaline, salbutamol
  • Increase cyclic AMP levels in smooth muscle
  • Adverse effects of tachycardia, hypertension, hyperglycaemia
28
Q

Calcium channel blockers as uterine relaxants (tocolytics):
• Name 2 examples
• Mechanism

A
  1. Nifedipine (current drug of choice for preterm labour)
  2. Magenisum sulphate

• Prevent intracellular calcium increase in smooth muscle

29
Q

Which NSAIDs act as a uterine relaxant (tocolytics)? Action?

A
  • Indomethacin

* Inhibit prostaglandin biosynthesis

30
Q

Name an oxytocin receptor antagonist used as uterine relaxant (tocolytics)

A

Atosiban

31
Q

How are nitrates used as uterine relaxants (tocolytics)?

A
  • Nitric oxide (NO) donors

* Nitroglycerine patch

32
Q

What is dysmenorrhoea?

A

Painful periods

33
Q

What is menorrhagia?

A

Excessive blood loss

34
Q

What is the cause for dysmenorrhoea and menorrhagia?

A

Prostaglandins

imbalance of prostaglandin E vs prostaglandins F in endometrium

35
Q

Which NSAIDs are used to treat menstrual symptoms?

A
  1. Ibuprofen
  2. Naproxen
  3. Mefenamic acid

• Effective for pain relief, unclear whether via uterine relaxation or central analgesic effect

36
Q

What reduces blood loss by ~ 10% in menstrual symptoms?

A

Antifibrinolytics

e.g. tranexamic acid

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