Which of the following initiates the birth process?
A) CRH targets the fetal anterior pituitary to release ACTH.
B) Progesterone production levels decrease around six months, while estrogen levels keep increasing making the uterus more likely to contract.
C) The hypothalamus signals the posterior pituitary to secrete oxytocin.
D) All of these happen to initiate the birth process.

Question

Quizplus · Accepted Answer

The hypothalamus in the fetus releases corticotropin-releasing hormone (CRH) due to stress (confines of a small space relative to the growing fetus). CRH targets the fetal anterior pituitary to release ACTH. ACTH, in turn, targets the fetal adrenal glands so that glucocorticoids are released. The fetal glucocorticoids travel to the placenta. The fetal glucocorticoids cause the placenta to adjust the level of its hormones. Progesterone production levels off at around six months, while estrogen levels keep increasing. Estrogen makes the uterus more irritable (likely to contract), while progesterone suppresses contractions. So, estrogen begins to have an increased effect encouraging uterine contractions as the pregnancy reaches full term. The placenta and the membranes associated with it also produce prostaglandins that make the myometrium more likely to contract. Smooth muscle of the myometrium stretches more and more as the pregnancy progresses. Stretch receptors in the myometrium signal the mother's hypothalamus. The hypothalamus signals her posterior pituitary to secrete oxytocin. This hormone promotes labor (uterine contractions to bring about birth) in two ways: oxytocin directly stimulates the myometrium to contract, and it stimulates the placenta to produce more prostaglandins. Uterine contractions cause the head of the fetus to press 3 Harder on the cervix which causes more signals to be sent to the hypothalamus, so more oxytocin is released. The head pushing on the cervix also stimulates the cervix to release prostaglandins. This becomes a positive feedback mechanism that will not end until the fetus is expelled from the uterus.

Which of the Following Initiates the Birth Process