FErtilization

Question 1

Where does the extraembryonic tissue derive from?

Answer 1

It comes from the outer cell mass also known as the trophoblast. It will give rise to the placenta and can give rise to abnormal growth labeled the gestational trophoblastic tumor.

Question 2

How are fraternal twins gestationally?

Answer 2

They have separate amniotic cavities and shared or separate placenta.

Question 3

What is the cumulus oophorus?

Answer 3

It is the outer layer of the oocyte also known as the corona radiata.

Question 4

What happens in each of the 3 weeks?

Answer 4

1st week: fertilization which ends with implantation. Outer cell mass and inner cell mass is established.

2nd week: outer cell mass and outer cell mass differentiate into the two layers. You get a bilaminar disk (epiblast and hypoblast) along with extraembryonic structures.

3rd week: epiblast undergoes gastrulation.

Question 5

What happens during fertilization?

Answer 5

1. With whipping tail, the sperm penetrates the cumulus oophorus (corona radiata) which secretes chemoattractants and is made up of follicular cells which support the oocyte.
2. Sperm binds to ZP3 sperm receptors and release acrosomal enzymes that digest the pellucida.
3. The sperm penetrates the ZP and fuses with the oocyte membrane.
4. Fast block: a wave of depolarization in the plasma membrane. Slow block: INflux of calcium causes cortical reaction (cortical granules containing lysosomal enzymes are released which makes the ZP inpenetrable).
5. The oocyte completes meiosis II.