Intro

Question 1

Describe the route of the oocyte

Answer 1

The oocyte is created in the ovaries. Sperm travels through the fallopian tubes to fertilise the egg. Once fertilised it travels down the oviduct, developing from egg to blastocyst until it implants in the uterus at around 4-5 days.

Question 2

Why can we study egg development?

Answer 2

Because the cell is not attached to the mother it can be removed for studies. It allows us to follow the development of a fertilised egg pre-implantation.

Question 3

Summarise what happens pre-implantation.

Answer 3

Polarisation, compaction and cavitation.

Three distinct lineages have been established.

Question 4

What are the 3 distinct lineages that are established and summarise how.

Answer 4

Trophectoderm (TE), primitive endoderm (PrE), epiblast (EPI). Defined and maintained by mutually antagonistic expression of key genetic determinants - e.g. Cdx2 and Oct4.

Question 5

What are the two main cell fate decisions?

Answer 5

• Segregation of trophectoderm from inner cell mass (shortly after 8 cell stage, complete by 32)
• Segregation of primitive endoderm from epiblast (from early morula, complete by implantation)

Question 6

How are these cell fates determined?

Answer 6

Unsure of how, different models still argued but microenvironment, polarity and history all may be involved in regulating these decisions.