Question

Contraceptives oral pills help in birth control by
A. Killing the sperm in the uterus
B. Preventing implantation
C. Preventing ovulation
D. Both B and C

Answer 1

Hint: Pregnancy can be avoided if there is no egg to be fertilized. In case the egg is fertilized by the sperm, the failure of its embedding into the uterine lining can cause miscarriage and hence, prevent pregnancy. Use of pills also plays an important role in the process.

Complete answer: Birth control pills, also known as oral contraceptives, are used to prevent pregnancy by the secretion of hormones which prevent fertilization of an egg in the fallopian tube.
a) Ovulation: Ovulation is the process of rupture of the follicle from the ovaries of a female which results in the release of an egg from one of the ovaries per month. The egg, thus released, travels down the fallopian tube and is picked up by cilia of an oviducal funnel of the oviduct. It is when the fertilization by a sperm cell may occur. The egg fertilized in the fallopian tube, which is called a zygote, soon starts dividing. By the time it reaches the uterus it forms a small hollow mass of numerous cells and is called the blastocyst.
b) Implantation: It is the process of fixing the blastocyst to the wall of the uterus. The contraceptive pills work by either preventing ovaries from releasing an egg or by thickening the mucus membrane in the neck of the womb making it harder for the sperm cells to reach the egg. The thickened uterine lining also lessens the chances of survival of the fertilized egg.
Hence, the correct answer is option D.

Note: Following are the types of oral contraceptive pills: monophasic pills, biphasic pills and triphasic pills. There are other techniques involved to control birth such as the use of intrauterine devices, vasectomy, etc.