Fertilisation and Conception

Question 1

Fertilisation stages

Answer 1

1. Capacitation
2. Acrosome reaction
3. Fusion of membranes
4. Cortical reaction

Question 2

Capacitation

Answer 2

Surface of spermatozoa undergoes changes to facilitate acrosome reaction and sperm entry into secondary oocyte

Question 3

Acrosome Reaction

Answer 3

The enzymes from the acrosome (bag at the tip of spermatozoa) digest a pathway through the follicular cells and zona pellucida to the secondary oocyte

Question 4

Fusion of membranes

Answer 4

The plasma membranes of spermatozoa and oocyte fuse together and nucleus of sperm cell enters oocyte’s cytoplasm. This triggers membrane depolarization which acts as a fast block to prevent further sperm entry. This also completes meioisis II of secondary oocyte and triggers cortical reaction.

Question 5

Cortical reaction

Answer 5

Slow and permanent change to the follicular cells to prevent any other sperm cell from entering oocyte.