Fertilisation to trilaminar embryo

Question 1

What is the zona pellucida?

Answer 1

Extracellular matrix which surrounds the oocyte

Question 2

How many zona pellucida glycoproteins are there and what are they called?

Answer 2

4: ZP1, ZP2, ZP3 & ZP4

Question 3

What processes does the zona pellucida play an important role in?

Answer 3

development and growth of the embryo, protection, fertilisation, help binding of sperm and preventing polyspermy.

Question 4

Where are acrosomal enzymes released from and what is their function?

Answer 4

They are released from the sperm head and they digest the zona pellucida to help the sperm penetrate into the oocyte.

Question 5

What two processes does sperm trigger when it enters the oocyte?

Answer 5

Completion of meiosis II and release of cortical granules by oocyte.

Question 6

What do cortical granules in the oocyte do?

Answer 6

Makes the zona pellucida impenetrable by other sperm cells.

Question 7

Where does fertilisation normally occur?

Answer 7

The ampulla

Question 8

Describe the process of sperm entering the oocyte.

Answer 8

1) Sperm binds in a human specific interaction with ZP3
2) Acrosomal enzymes are released and the sperm digests its way into egg
3) Egg and sperm plasma membrane fuse and sperm contents enter the egg
4) Sperm entry triggers completion of meiosis 2 and release of cortical granules by oocyte