Signals from a fully developed fetus and placenta ultimately lead to parturition which requires the release of?

Explanation

Note: Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex. This triggers release of oxytocin from the maternal pituitary. Oxytocin acts on the uterine muscle and causes stronger uterine contractions, which in turn stimulates further secretion of oxytocin. The stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger and stronger contractions. This lead to expulsion of the baby out of the uterus through the birth canal.The correct option is: b) Oxytocin from maternal pituitaryExplanation of each option:a) Estrogen from placenta:Estrogen plays a crucial role in pregnancy and childbirth, but it is not directly responsible for initiating parturition (the process of childbirth). During pregnancy, the placenta produces and releases estrogen, which helps maintain the pregnancy, support fetal development, and prepare the mother's body for labor. However, the release of estrogen from the placenta alone does not trigger the onset of labor.b) Oxytocin from maternal pituitary:This is the correct option. Oxytocin is a hormone produced by the hypothalamus and released from the posterior pituitary gland. As the pregnancy nears full-term, the fully developed fetus and placenta release certain signals that lead to an increase in maternal oxytocin production and sensitivity to oxytocin. This increased oxytocin release from the maternal pituitary gland plays a central role in initiating and regulating contractions during labor. Oxytocin stimulates the uterine muscles to contract, which helps progress labor and eventually leads to childbirth.c) Oxytocin from foetal pituitary:The fetal pituitary gland does produce oxytocin, but it does not play a significant role in initiating labor. The primary source of oxytocin responsible for triggering labor is from the maternal pituitary gland.d) Relaxin from placenta:Relaxin is another hormone that is released during pregnancy, mainly by the corpus luteum in the ovaries and the placenta. It helps to relax the ligaments and tissues in the pelvic region, preparing the mother's body for childbirth. However, relaxin's role is not to initiate labor directly. Instead, it aids in creating the necessary physical conditions for a smoother and less obstructed passage during delivery.In summary, the correct option is (b) Oxytocin from maternal pituitary. Signals from the fully developed fetus and placenta lead to an increase in maternal oxytocin production and sensitivity, which initiates labor by stimulating uterine contractions, eventually leading to childbirth.