Question

What is fertilization and explain it with taking an example of human beings?

Answer 1

A single egg comes out of the ovary every month, and reaches the fallopian tube. Sperms reach the fallopian tube where a sperm fertilizes the egg. This results in formation of zygote.

• In humans, fertilization occurs in the fallopian tubes of the female reproductive tract. It takes place within hours following sexual intercourse. Approximately 300 million sperm are released into a female's vagina during intercourse. However, only one of these sperm can actually fertilize the single female egg cell (also called an ovum). The successful sperm cell must enter the uterus and swim up the fallopian tube to meet the egg cell. There it passes through the thick coating surrounding the egg. This coating is known as the zona pellucida.
• The head of the sperm cell contains enzymes (certain types of chemicals) that break through the zona pellucida and make it possible for the sperm to penetrate into the egg. Once the head of the sperm is inside the egg, the tail of the sperm falls off. The outside of the egg then thickens to prevent another sperm from entering.
• In humans, a number of variables affect whether or not fertilization occurs following intercourse. One factor is a woman's ovulatory cycle. The ovulatory cycle is the series of events that bring about the ripening of an egg and its release from the ovaries. Human eggs can be fertilized for only a few days after ovulation, which usually occurs only once every 28 days.