Question

Which of the following sequence shows the correct progressive sequence of foetal ejection reflex and parturition

• A. Fully developed foetus → Stretching of the cervix →Hypothalamus →Posterior pituitary →Contraction of the myometrium → Parturition
• B. Fully developed foetus → Stretching of the cervix →Hypothalamus→ anterior pituitary →Contraction of the myometrium → Parturition
  
• C. Fully developed foetus → Stretching of the cervix →Hypothalamus→ anterior pituitary →Contraction of the endometrium → Parturition
  
• D. Fully developed foetus → Stretching of the cervix →Hypothalamus →Posterior pituitary →Contraction of the myometrium → ovulation
  

Answer 1

The correct option is A Fully developed foetus → Stretching of the cervix →Hypothalamus →Posterior pituitary →Contraction of the myometrium → Parturition

Parturition means childbirth. When the foetus is fully developed, the adrenal gland of the developing foetus starts releasing androgen, which is readily taken by the placenta and converted into estrogen.

Estrogen now acts as a mediator, it antagonises relaxation by inhibiting progesterone (pregnancy hormone, which keeps the endometrium relaxed whole through the gestation period).

Estrogen also induces the expression of the oxytocin receptor on the myometrial layer of the uterus.

Oxytocin contracts the smooth muscles and gradually the foetus starts expelling out and it scratches the wall of the cervical canal.

The first step of parturition starts with the onset of labour, and it continues until the cervix is dilated. The cervix will dilate with a rate of 1 cm per hour in a first time parturition and 2 cm per hour in successive parturitions.

In the phase of expulsion, the baby’s head moves down through the vagina. Where a high contraction is needed, then the baby is expelled out.

Stretch receptors on the wall of the cervical canal give a stimulus or positive feedback to the mother’s pituitary to release more and more oxytocin and hence more contraction of the endometrium. This causes the expulsion of the baby out of the mother’s womb.