Reproduction - parturition

Question 1

What leads to the onset of parturition?

Answer 1

Controlled by the foetus when it is stressed and releases foetal ACtH. This increases cortisol and reduces progesterone.

This reduction of progesterone leads to an increase in E2, and increase in prostaglandins. This starts myometrial contractions but reduces the threshold, putting pressure on the cervix which increases the oestrogen levels.

Question 2

What are the 3 stages of parturition?

Answer 2

1. Regular uterine contraactions, cervical shortening and dilation (2-6 hours)
   - Latent phase
   - Active phase
2. Complete delivery of foetus, rupture of membranes and abdominal contractions (30-120 mins later)
3. Delivery of placenta (5-8hours)

Question 3

What stimulates myometrial contractions?

Answer 3

The muscle cells grow significantly during pregnancy.

Oxytocin leads to an increase in Ca2+ levels and allows the expression of ATPase. The levels of oxytocin increases dramatically as the pressure is applied on the cervix, leading to more oxytocin release.

Question 4

What is brachystasis?

Answer 4

The myometrial cells contracts and shorted but do not return to orginal length (shorter birth canal)

Question 5

What is the hormonal control of parturition?

Answer 5

Prostaglandins (release of Ca2+)
Oxytocin (lowers excitation threshold of myometrium cells)

Question 6

What is primary uterine inertia?

Answer 6

Failure to initiate contractions due to a lack of oxytocin and/or receptors

OR

lack of induction by foetus

Question 7

What is secondary uterine intertia?

Answer 7

Starts well but contractions stop, so an injection/drip of oxytocin is needed.

Prostaglandins can be placed on cervix to help soften