Question

Signals from the fully developed fetus and placenta ultimately lead to parturition, which requires the release of
A. Relaxin from the placenta.
B. Estrogen from the placenta.
C. Oxytocin from maternal pituitary.
D. Oxytocin from fetal pituitary.

Answer 1

Hint: Oxytocin is a peptide hormone and neuropeptide. It is normally produced in the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, sexual reproduction, childbirth, and the period after childbirth.

Complete step-by-step answer:
The process of giving birth to a baby is called parturition. It starts with a rise in oestrogen/progesterone ratio, and increases in the level of oxytocin secretion by the mother. Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed foetus and the placenta, which induces mild uterine contractions called foetal ejection reflex. This reflex triggers the release of oxytocin from the maternal pituitary. This hormone acts on uterine muscle and causes more contractions, which in turn secrete more oxytocin.
The stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger and stronger contractions which leads to the expulsion of the baby.
Oxytocin has been best known for its roles in female reproduction. It is released in large amounts during labour. It is a facilitator for childbirth and breastfeeding. One of the oldest applications of oxytocin as a proper drug is as a therapeutic agent during labour and delivery.
Oxytocin injection is used to begin or improve contractions during labour. Oxytocin also is used to reduce bleeding after childbirth. It also may be used along with other medications or procedures to end a pregnancy. Oxytocin is in a class of medications called oxytocic hormones.

Hence, the correct option is C.

Note: Oxytocin secreted from the pituitary gland cannot re-enter the brain because of the blood-brain barrier. Instead, the behavioural effects of oxytocin are thought to reflect release from centrally projecting oxytocin neurons, different from those that project to the pituitary gland.