Read the given passage and answer the following questions :
The average duration of human pregnancy is about 9 months which is called the gestation period. Vigorous contraction of the uterus at the end of pregnancy causes expulsion/delivery of the foetus. This process of delivery of the foetus (childbirth) is called parturition. 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 leads to expulsion of the baby out of the uterus through the birth canal – parturition. Soon after the infant is delivered, the placenta is also expelled out of the uterus. The mammary glands of the female undergo differentiation during pregnancy and starts producing milk towards the end of pregnancy by the process called lactation. This helps the mother in feeding the new- born. The milk produced during the initial few days of lactation is called colostrum which contains several antibodies absolutely essential to develop resistance for the new-born babies. Breast-feeding during the initial period of infant growth is recommended by doctors for bringing up a healthy baby.
Foetal ejection reflex triggers the release of:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Oxytocin
The passage states that signals from the fully developed foetus and the placenta induce mild uterine contractions called the foetal ejection reflex, and that “This triggers release of oxytocin from the maternal pituitary”.
Oxytocin acts on the muscles of the uterus and causes stronger contractions. These contractions cause more oxytocin to be released, so the contractions keep getting stronger until the baby is pushed out through the birth canal.
Option (1) Cortisol — Incorrect. Cortisol is one of the hormones of the neuroendocrine mechanism of parturition, and its level rises during pregnancy. It is not, however, the hormone that the foetal ejection reflex releases from the pituitary.
Option (2) Oxytocin — Correct. Oxytocin is released from the maternal pituitary in response to the foetal ejection reflex. It brings about the stronger uterine contractions of childbirth.
Option (3) Prolactin — Incorrect. Prolactin is a pituitary hormone whose level rises during pregnancy, but it is linked with milk formation in the mammary glands, not with the contractions of childbirth.
Option (4) Vasopressin — Incorrect. Vasopressin (antidiuretic hormone, ADH) is released from the posterior pituitary, but it acts on the kidney to reduce water loss in urine. It has no role in the reflex of childbirth.