Question

Describe the process of parturition in humans.

Answer 1

At the end of an average 9 months of gestation, vigorous uterine contractions lead to the delivery of the foetus. This process is called parturition.

Parturition is a neuroendocrine mechanism and is started by the signals from the fully developed foetus and the placenta, which produce the foetal ejection reflex. A developing foetus secretes hormones from its adrenal glands. These hormones diffuse into the maternal blood and accumulate to stimulate the release of oxytocin (birth hormone) from the mother’s posterior pituitary.

Oxytocin causes the forceful contraction of smooth muscles of the myometrium, called labour pains, which pushes the young gradually out through the dilated cervix (caused by relaxin) and vagina, with the head foremost. Uterine contraction, in turn, stimulates further secretion of oxytocin. The stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger and stronger contractions. It is aided by a reflex and voluntary contraction of abdominal muscles. The foetal membranes burst and amniotic fluid is released but foetal membranes remain behind. This expulsion stage lasts about 20 minutes to one hour. It is followed by a placental stage of 10-45 minutes during which the umbilical cord, placenta and foetal membranes are expelled as decidua or after birth.

It is because, after the childbirth, the uterus reduces in size causing detachment of placenta. The umbilical cord is tied and then cut which finally shrinks into a depressed scar called umbilicus or navel.