Which factor does NOT contribute to parturition?
A) The increasing ACTH (adrenocorticotropic hormone) secretion by the fetal pituitary causes the fetal adrenal glands to secrete more cortisol, which diffuses into the maternal circulation.
B) Cortisol increases oxytocin and progesterone secretion, increasing plasma progesterone levels.
C) The uterus stretches as the pregnancy progresses, initiating nerve impulses that stimulate oxytocin secretion from the posterior pituitary lobe.
D) The number of oxytocin receptors on uterine muscle fibres increases, causing the uterus to become more sensitive to the effects of oxytocin.

Question

Quizplus · Accepted Answer

ACTH and cortisol secretion contribute to parturition by promoting fetal maturation and initiating contractions, and uterine stretching and oxytocin secretion also play important roles in initiating and maintaining labor. However, cortisol does not increase plasma progesterone levels; in fact, cortisol levels increase as progesterone levels decrease, as progesterone inhibits the cortisol-producing pathway. Cortisol increases the number and sensitivity of oxytocin receptors on uterine muscle fibres, but this is a downstream effect that is not directly related to progesterone levels.

Which Factor Does NOT Contribute to Parturition