Fertilisation

Question 1

When and where does fertilisation occur?

Answer 1

• in the outer third of the fallopian tube
• when the nuclei of the sperm and egg fuse to form a zygote

Question 2

What happens after semen is deposited in the vagina?

Answer 2

• sperm move through the cervix, uterus and into the fallopian tubes until they reach the egg

Question 3

What happens to the egg during fertilisation?

Answer 3

• the egg, surrounded by follicle cells, is sucked into the fallopian tube by action of the fimbriae

Question 4

What happens during step 1 of fertilisation?

Answer 4

1. thousands of sperm surround the egg

Question 5

What happens during step 2 of fertilisation?

Answer 5

2. hydrolytic enzymes, released from the acrosomes, break down the follicle cells

Question 6

What happens during step 3 of fertilisation?

Answer 6

3. only one sperm penetrates the membrane of the egg; the tail is discarded

Question 7

What happens during step 4 of fertilisation?

Answer 7

4. the nuclei of the sperm and egg fuse, forming a diploid zygote

Question 8

What happens during step 5 of fertilisation?

Answer 8

5. a fertilisation (egg) membrane forms immediately, which prevents other sperm from entering the egg