Uterine Motility Flashcards
What is the myometrium?
The inner layer of the uterus with layer of smooth muscle
Why are gap junctions important in labour?
They are required for depolarisation to spread between all the uterine smooth muscle
Which gap junction protein is important in the uterus?
Connexin 43
Why is connexin 43 unique?
It is hormonally controlled
What is fundal dominance?
More contractions in the fundus of the uterus that move downwards during labour
May be caused by more gap junctions present in the fundus
What are the sympathetic receptors found in the uterus and what effect do they have?
alpha - contraction
beta - relaxation
What determines whether of not the SNS causes relaxation or contraction of the uterus?
The ratio of receptor types which is influenced by hormones
Which pituitary hormones cause contraction of the uterus?
ADH
Oxytocin
What effects oxytocin receptor numbers?
At term, there is falling progesterone levels with sustained oestrogen levels
Stimulates prostaglandin biosynthesis which results in oxytocin receptor expression
What is the effect of oxytocin on the uterus?
Stimulates increasingly regular, co-ordinated contractions that travel from the fundus to the cervix (fundal dominance)
Uterus relaxes completely between contractions
What are uterine stimulants used for?
Abortion
Induction and acceleration of labour
Contract uterus after delivery to control postpartum bleeding
What are uterine relaxants used for?
Menstrual cramps
Prevention of preterm labour
Facilitate obstetric manouvers
Counteract uterine hyperstimulation
What is oxytocin used for clinically?
Given IV to induce labour
IV or IM to control postpartum haemorrhage
What is ergometrine used for now a days?
Misscarriage
What are the uses of misoprostol in obstetrics?
Abortion
Induction of labour
Postpartum haemorrhage
Why is ergometrine not used for women with living foetuses?
Powerful uterine contractions will compromise foetus
What is syntometrine?
Oxytocin and ergometrine combination used for 3rd stage of labour
What differing effects do prostaglandins E and F have?
E - vasodilator
F - vasoconstrictor
Both act on cervical ripening and induce oxytocin receptors
What is the decidua?
Pregnant endometrium
Give an example of a naturally occurring prostaglandin?
Dinoprostone
What is carboprost?
Synthetic analogue of prostaglandin F2a
What is Gemeprost?
Synthetic analogue of prostaglandin E1
Which type of prostaglandin is dinoprostone equivalent to?
E2
Which drug is misoprostol used with in abortion to sensitise the uterus?
Mifepristone
What effect does a rise in cAMP have on smooth muscle?
Relaxation
How do B-agonists work as uterine relaxants?
They bind to receptors causing increase in cAMP which relaxes muscle
Give 3 examples of B-agonists
Ritodrine
Terbulaine
Salbutamol
How do calcium channel blockers cause uterine relaxation?
Prevent intracellular calcium increase in smooth muscle which causes contraction
How do NSAIDs cause relaxation of uterine smooth muscle?
Inhibit prostaglandin biosynthesis
Give an example of an NSAID used in obstetrics
Indomethacin
Name an oxytocin receptor antagonist
Atosiban
Name a drug used to prevent excess blood loss during mensturation
Tanexamic acid
Name the different types of drugs that are uterine relaxants
Calcium channel blockers
NAIDS
Nitrates
B-agonists
Name the different types of drug that are uterine stimulants
Ergometrine
Prostaglandins e.g. misoprostol
Oxytocin
Give an example of a nitrate uterine relaxant
Nitroglycerine patch
What may be responsible for dysmenorrhoea?
Imbalance between prostaglandin E and F in endometrium
Name an antifibrinolytic used in menorrhagia
Tranexamic acid
Why are NSAIDS used for dysmenorrhoea?
Uterine relaxation
Central analgesic effect
