Question

The expulsion of completely developed foetus from the uterus is known as
A. Ovulation
B. Oviposition
C. Gestation
D. Parturition

Answer 1

Hint: The average time period of human pregnancy is normally about 9 months or can be said as 38weeks/266 days after fertilisation which is called the gestation period. Vigorous contraction of the uterus at the end of pregnancy period causes expulsion and delivery of foetus.

Complete Answer:
The signals for the delivery of foetus comes from the fully developed foetus and placenta which causes mild uterine contraction called foetal ejection reflex. This causes the release of oxytocin from the maternal pituitary. Oxytocin functions on uterine muscles and causes stronger uterine contractions, which in turn leads to secretion of oxytocin. The stimulatory reflex between the uterine contraction and oxytocin secretion goes on and results in stronger and stronger contraction and leads to expulsion of foetus.

Now let us find solution from given options:
- Ovulation: The process when graafian follicle gets ruptured and leads to release of ovum , it is termed as ovulation. This process occurs on the 14th day.
- Oviposition: It is defined as the expulsion of the egg from the structure called an oviduct.
- Gestation: The average time period of human pregnancy is normally about 9 months or can be said as 38 weeks / 266 days after fertilisation which is called the gestation period.
- Parturition: When there occurs strong contraction of the uterus at the time of end of pregnancy it results in the delivery of foetus. This process of delivery is termed as parturition.

Our required option is D that is Parturition.

Note: Parturition starts with the dilation in which the posterior lobe of the pituitary secretes the oxytocin hormone (birth releasing hormone). This hormone is unique in itself due to the reason that it is positively regulated (known as positive feedback regulation) that means the more the concentration of oxytocin, the more it will be secreted by the posterior lobe of the pituitary.