Fertilisation

Question 1

Why do sperm swim towards the oviducts?

Answer 1

The oocytes release chemoattracts.

Question 2

Describe capacitation.

Answer 2

Must happen for sperm to fertilise egg. The acrosome membrane becomes more permeable as cholesterol and glycoproteins are removed.

Question 3

Describe the acrosome reaction.

Answer 3

The acrosome releases processes that digest the corona radiata and acrosin which digest the zona pellucida. Cell membrane and sperm was fuse and the head sinks into the cytoplasm of the procure. The oocyte completes meiosis 2 and releases a second polar body, becoming an ovum.

Question 4

Describe the cortical reaction and why it occurs.

Answer 4

Cortical granules made from calcium ions fuse with the cell membrane and release enzymes by exocytosis. The zona pellucida hardens and expands, making the fertilisation membrane. This is so no sperm can enter and polyspermy is impossible.

Question 5

Describe the journey the zygote takes once the genetic material of the oocyte and sperm fuse.

Answer 5

The zygote moves down the oviduct and divides by mitosis in a process called cleavage. A solid ball called a morula forms. Then this develops into a hollow ball called a blastocyst. The blastocyst has an outer layer called the trophoblast, surrounding the chorion. Trophoblastic villi are formed.

Question 6

What is the role of the trophoblastic villi?

Answer 6

Produces a larger SA and attaches to the endometrium to gain nutrients.

Question 7

What is implantation?

Answer 7

The embedding of the blastocyst into the endometrium wall. The endometrium has thickened and got an increased blood supply.