Question

Signals from the fully developed foetus and placenta ultimately lead to parturition which requires the release of

• A. Oxytocin from maternal pituitary
  
• B. Relaxin from placenta
  
• C. Estrogen from placenta
  
• D. Oxytocin from foetal pituitary
  

Answer 1

The correct option is A Oxytocin from maternal pituitary


Fetal-ejection reflex
The signals for parturition originate from the fully developed foetus and the placenta which induce mild contractions in the uterus called fetal ejection reflex.

Role of oxytocin in parturition
A fully developed fetus pushes down the birth canal, causing stretching of the cervix. This generates nerve impulses that stimulate the hypothalamus. Hypothalamus in turn causes the posterior lobe of the maternal pituitary to release oxytocin, the birth hormone. Oxytocin causes the uterine muscles to contract to lead to parturition.

Relaxin
Relaxin is secreted by the corpus luteum in the ovary and the placenta. It relaxes the pelvic ligaments and widens the cervix for helping in childbirth.

Estrogen
Estrogen is the female sex hormone produced by the ovaries, corpus luteum, and placenta.

• It is responsible for endometrial thickening.
• It helps in repairing the wall of the uterus.
• It also helps in the development of secondary sexual characteristics in females such as widening of pelvis and hips, high pitched voice, initiation of the menstrual cycle, the growth of mammary glands (breasts), etc.

Final answer

c. Oxytocin from maternal pituitary