Hormone control of parturation
a) Dilation of the cervix before delivery stimulate the hypothalamus which result in the release of oxytocin that lead to uterine contraction that push the head of fetus more into cervix which lead to stimulate more oxytocin releas. Oxytocin also stimulate the uterus to release PG causing more uterine contraction.
b) The number of oxytocin receptors are markedly increased in response to estrogen and relaxin at late pregnancy which increase the uterine response to oxytocin one hundred time compare to normal women.
2) Effect of prostaglandins
In response to oxytocin, the myometrium of uterus secret PG which through a paracrine stimulate further uterine contractions.