Uterine Motility Flashcards
What are the layers of the uterus called (from outward most layer inwards)?
- Perimetrium (serosa)
- Myometrium
- Endomrtrium
What layer of the uterus is a single thin layer of epithelium?
Perimetrium (serosa) (not evident clinically)
What does the endometrium become during pregnancy?
Decidua
What is the cervix mostly made up of?
Connective tissue and blood vessels (a little bit of smooth muscle)
What do uterine contractions depend on?
Gap junctions for phasic propagation of depolarisation
What is the name of the gap junction present in the uterus?
Connexin 43
How is uterine SM induced?
Hormones during pregnancy (connexin 43 not active after)
What alpha-adrenoceptors cause?
Contraction
What beta-adrenoceptors cause?
Relaxation
What is the ratio of alpha and beta sympathetic receptor types influenced by?
Hormonal status
How many amino acods make up oxytocin and ADH?
9 amino acid peptides (only 2 are different between them)
What are the effects of oxytocin and ADH on the uterus?
They stimulate contraction
What are oxytocin’s effect on the uterus dependant on?
Receptor numbers which is influenced by sex hormone levels
What tissues does oxytocin affect?
- Uterine muscles
- Mammary glands
What happens to the number of uterine receptors in the uterus at term?
Increases drastically (in order to induce contractions)
What does oxytocin stimulate the biosynthesis of at term?
Prostaglandins
What happens to progesterone levels at term?
They start to fall
Describe the uterine contractions?
- Stimulated by oxytocin
- They increase in regularity towards parturition and are co-ordinated and travel from the fundus to the cervix (fundal dominance)
- Uterus relaxes completely between contractions
What are uterine stimulants (oxytocics) used for?
- Induce abortion
- Induce and accelerate labour
- Contract the uterus after delivery to control postpartum haemorrhage (PPH)
What are uterine relaxants (tocolytics) used for?
- Menstraul cramps / dysmenorrhoea
- Prevent or treat preterm labour
- Facillitate obstetric manoeuvres
- Counteract (iatrogenic) uterine hyperstimulation
What do uterine stimulants (oxytocics) comprise of?
- Oxytocin
- Ergometrine
- E and F series prostaglandins
What is the main purpose of ergometrine?
- To stop bleeding post partum (contract uterus)
- Causes sustained powerful contractions
- Also used for bleeding in early pregnancy (oxytocin not effective)
When is ergometrine not advised?
HYpertension can cause nasea/vomitting
Where are prostaglandins synthesised?
Endometrium and cervix
What will prostglandins do for pregnancy?
Stimulates labour
What do the F series of prostaglandins do?
Vasoconstrict (PGF2a)
WHat do the E series of prostaglandins do?
Vasodilate (PGE2 - helps to ripen and soften cervix as well 20x more powerful)
What is Dinoprostone used for?
To induce rapid uterine contractions (equivelant to PGE2)
What is Carboprost used for?
- Analogue of PGF2a
- Injected to uterus
- Induces rapid uterine contractions (C-section)
What are synthetic analogues of PGE1?
- Gemeprost
- Misoprostol (more widely used)
What does misoprostol used for?
- Slow effect
- Treat peptic ulcers
- Medical abortion, myometrium sensitised by mifepristone (progesterone receptor antagonist) then misoprostol
- Induction of labour
- Control of PPH
How is misoprostol administered?
- Oral
- Vaginal
- Sublingual
- Rectal
SLOWLY ABSORBED so NOT IV/IM
Wha are some examples of types of Uterine relaxants (tocolytics)?
- B2-agonists
- CCBs
- NSAIDs
- Oxytocin receptor antagonists
- Nitrates
What are some adverse effects of B2 agonists?
- Tachycardia
- Hypertension
- Hyperglycaemia
What are some examples of B2 agonists?
- Ritodrine, terbutaline, salbutamol
What are some examples of CCBs?
- Nifedipine (current choice of drug for preterm labour)
- Magnesium sulphate (also vasodilate so baby will not have compromised blood flow)
What are some examples of NSAIDs used as tocolytics?
- Indomethacin (not in obstetrics used as it can cause ductus arteriosus to stay open)
- Inhibit prostaglandin biosynthesis
What is an example of a oxytocin receptor antagonist?
Atosiban
What are some examples of Nitrates used as tocolytics ?
- Nitric oxide (NO) donors
- Nitroglycerine patch
- Weak
What medication is used for dysmenorrhoea and can reduce period blood loss by almost 50%?
Antifibrinolytic i.e tranexamic acid enhances vit K pathway w/o increasing blood clots
