Question 1

Where does fertilisation take place in humans?

Accepted Answer

Fertilisation takes place in the ampullary region of the fallopian tube. Both the ovum released by the ovary and the sperms must reach the ampulla at the same time; the zygote then moves down the tube towards the uterus while it divides.

Question 2

What is the difference between a morula and a blastocyst?

Accepted Answer

A morula is the embryo at the 8–16 blastomere stage formed by cleavage. As it moves into the uterus it continues to divide and becomes a blastocyst, in which the cells are arranged into an outer trophoblast and an inner cell mass.

Question 3

What is implantation?

Accepted Answer

Implantation is the attachment of the blastocyst to the uterine wall. The trophoblast attaches to the endometrium, the uterine cells divide rapidly and cover the blastocyst, and it becomes embedded in the endometrium. This leads to pregnancy.

Question 4

How does the ovum prevent entry of more than one sperm?

Accepted Answer

When a sperm comes in contact with the zona pellucida layer of the ovum, it induces changes in the membrane that block the entry of additional sperms, ensuring that only one sperm fertilises the ovum.

Fertilisation to Implantation Lab — From Ampulla to Endometrium

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