Question

Capacitation refers to changes in the
A. Ovum after fertilization
B. Sperm after fertilization
C. Sperm before fertilization
D. Ovum before fertilization

Answer 1

Hint: Capacitation is the physiological changes occur in the spermatozoa to obtain the ability to penetrate and fertilize an egg. Capacitation is a biochemical process and only male gamete (sperm) undergoes the capacitation process.

Complete answer:
During copulation semen is released by the penis into the vagina of the female and this process is known as insemination. A human sperm can live for many weeks in male genital duct. When the ejaculation occurs the sperm lives for 24 to 48 hours. Sperms move in the liquid medium secreted by the female genital tract. Prostaglandins of semen help in the movement of spermatozoa.
When the sperm is released in the female genital tract, the capacitation of sperm occurs. This process involves:
- Removal of cholesterol membrane present over acrosome.
- Dilution of decapacitation factors takes place.
The entry of calcium ions in the sperm causes rapid whiplash movements of the tail part. Sperms swim through the vagina, cervix, uterus and reach the junction of isthmus and ampulla called ampullary-isthmic junction which is present in the fallopian tubes. The ovum released by the ovary also reaches to the ampullary-isthmic junction. In this region fertilization occurs. Ovum reaches the ampulla by the ciliary action of the ciliated columnar epithelium lining of the oviduct.

So the correct answer is option C.

Note: The ovum released by the ovary is in the secondary oocyte stage which is arrested in metaphase-2 stage. Fertilization can only occur if the ovum and the sperms are simultaneously transported to the ampullary-isthmic region.