Question

The foetal ejection reflex in humans stimulates ____________ to release the ____________ hormone, which is responsible for parturition.

• A. foetal pituitary, oxytocin
• B. maternal pituitary, oxytocin
  
• C. placenta, human Placental Lactogen (hPL)
  
• D. placenta, human Chorionic Gonadotropin (hCG)

Answer 1

The correct option is B maternal pituitary, oxytocin


The process of delivery of the foetus, due to the vigorous contraction of the uterus at the end of gestation is called parturition.

Parturition occurs due to a complex neuroendocrine mechanism that involves the mother, foetus, and placenta; stress plays a crucial role in activating a series of neurohormones. The signals for parturition originate from the fully developed foetus and the placenta, which cause mild uterine contractions called foetal-ejection reflex by inducing oxytocin release from the mother’s posterior pituitary. This results in vigorous contraction on the myometrium of the uterus.

At the same time, estrogen induces the expression of the ‘oxytocin receptors’ on the uterine wall, which helps in the secretion of more and more oxytocin and eventually more and more contractions in the smooth muscles of the myometrium leading to parturition.

The placenta acts as an endocrine tissue and secretes hormones like human Chorionic Gonadotropin (hCG), human Placental Lactogen (hPL), estrogen and progesterone.